Li-Jun Wan

Controlling the Compositional Chemistry in Single Nanoparticles for Functional Hollow Carbon Nanospheres

Co-reporter:De-Shan Bin, Zi-Xiang Chi, Yutao Li, Ke Zhang, Xinzheng Yang, Yong-Gang Sun, Jun-Yu Piao, An-Min Cao, and Li-Jun Wan

Journal of the American Chemical Society September 27, 2017 Volume 139(Issue 38) pp:13492-13492

Publication Date(Web):August 31, 2017

DOI:10.1021/jacs.7b07027

Hollow carbon nanostructures have inspired numerous interests in areas such as energy conversion/storage, biomedicine, catalysis, and adsorption. Unfortunately, their synthesis mainly relies on template-based routes, which include tedious operating procedures and showed inadequate capability to build complex architectures. Here, by looking into the inner structure of single polymeric nanospheres, we identified the complicated compositional chemistry underneath their uniform shape, and confirmed that nanoparticles themselves stand for an effective and versatile synthetic platform for functional hollow carbon architectures. Using the formation of 3-aminophenol/formaldehyde resin as an example, we were able to tune its growth kinetics by controlling the molecular/environmental variables, forming resin nanospheres with designated styles of inner constitutional inhomogeneity. We confirmed that this intraparticle difference could be well exploited to create a large variety of hollow carbon architectures with desirable structural characters for their applications; for example, high-capacity anode for potassium-ion battery has been demonstrated with the multishelled hollow carbon nanospheres.

Metal Octaethylporphyrin Nanowire Array and Network toward Electric/Photoelectric Devices

Co-reporter:Jin-Song Hu;Heng-Xing Ji

The Journal of Physical Chemistry C September 10, 2009 Volume 113(Issue 36) pp:16259-16265

Publication Date(Web):Publication Date (Web): August 17, 2009

DOI:10.1021/jp905818n

A vapor transfer deposition method was developed to fabricate metal (metal = Co, Ni, Cu, Zn, Mg) octaethylporphyrin (MOEP) nanowire arrays in large area on a variety of substrates. The formation process of MOEP nanowire arrays was investigated by time-dependently terminating deposition at various stages, based on which, a vaporization−condensation−recrystallization (VCR) mechanism was proposed to understand the formation of nanowires and thus guide the synthesis of three-dimensional (3D) sea urchin-like nanowire assemblies and two-dimensional (2D) nanowire networks. As application examples of these porphyrin nanostructures, the porphyrin nanowires demonstrated a good field emission property and the photoelectric device based on the 2D MOEP nanowire network was fabricated, showing a good light-induced signal amplification behavior.

Atom-Thick Interlayer Made of CVD-Grown Graphene Film on Separator for Advanced Lithium–Sulfur Batteries

Co-reporter:Zhenzhen Du, Chengkun Guo, Linjun Wang, Ajuan Hu, Song Jin, Taiming Zhang, Hongchang Jin, Zhikai Qi, Sen Xin, Xianghua Kong, Yu-Guo Guo, Hengxing Ji, and Li-Jun Wan

ACS Applied Materials & Interfaces December 20, 2017 Volume 9(Issue 50) pp:43696-43696

Publication Date(Web):November 27, 2017

DOI:10.1021/acsami.7b14195

Lithium–sulfur batteries are widely seen as a promising next-generation energy-storage system owing to their ultrahigh energy density. Although extensive research efforts have tackled poor cycling performance and self-discharge, battery stability has been improved at the expense of energy density. We have developed an interlayer consisting of two-layer chemical vapor deposition (CVD)-grown graphene supported by a conventional polypropylene (PP) separator. Unlike interlayers made of discrete nano-/microstructures that increase the thickness and weight of the separator, the CVD-graphene is an intact film with an area of 5 × 60 cm2 and has a thickness of ∼0.6 nm and areal density of ∼0.15 μg cm–2, which are negligible to those of the PP separator. The CVD-graphene on PP separator is the thinnest and lightest interlayer to date and is able to suppress the shuttling of polysulfides and enhance the utilization of sulfur, leading to concurrently improved specific capacity, rate capability, and cycle stability and suppressed self-discharge when assembled with cathodes consisting of different sulfur/carbon composites and electrolytes either with or without LiNO3 additive.Keywords: CVD-graphene film; interlayer; lithium−sulfur battery; polysulfide; separator;

Microbial-Phosphorus-Enabled Synthesis of Phosphide Nanocomposites for Efficient Electrocatalysts

Co-reporter:Tian-Qi Zhang, Jian Liu, Lin-Bo Huang, Xu-Dong Zhang, Yong-Gang Sun, Xiao-Chan Liu, De-Shan Bin, Xi Chen, An-Min Cao, Jin-Song Hu, and Li-Jun Wan

Journal of the American Chemical Society August 16, 2017 Volume 139(Issue 32) pp:11248-11248

Publication Date(Web):July 28, 2017

DOI:10.1021/jacs.7b06123

Transition-metal phosphides have recently been identified as low-cost and efficient electrocatalysts that are highly active for the hydrogen evolution reaction. Unfortunately, to achieve a controlled phosphidation of nonprecious metals toward a desired nanostructure of metal phosphides, the synthetic processes usually turned complicated, high-cost, and even dangerous due to the reaction chemistry related to different phosphorus sources. It becomes even more challenging when considering the integration of those active metal phosphides with the structural engineering of their conductive matrix toward a favorable architecture for optimized catalytic performance. Herein, we identified that the biomass itself could act as an effective synthetic platform for the construction of supported metal phosphides by recovering its inner phosphorus upon reacting with transition-metals ions, forming well-dispersed, highly active nanoparticles of metal phosphides incorporated in the nanoporous carbon matrix, which promised high catalytic activity in the hydrogen evolution reaction. Our synthetic protocol not only provides a simple and effective strategy for the construction of a large variety of highly active nanoparticles of metal phosphides but also envisions new perspectives on an integrated utilization of the essential ingredients, particularly phosphorus, together with the innate architecture of the existing biomass for the creation of functional nanomaterials toward sustainable energy development.

Investigation of Physical and Electronic Properties of GeSe for Photovoltaic Applications

Co-reporter:Shun-Chang Liu;Yang Mi;Ding-Jiang Xue;Yao-Xuan Chen;Chao He;Xinfeng Liu;Jin-Song Hu

Advanced Electronic Materials 2017 Volume 3(Issue 11) pp:

Publication Date(Web):2017/11/01

DOI:10.1002/aelm.201700141

AbstractGeSe is a promising absorber material for photovoltaic applications due to its attractive material, optical, and electrical properties as well as its low toxicity and earth abundance. The first GeSe-based solar cell with 1.48% efficiency has been recently reported through self-regulated rapid thermal sublimation. However, most of the fundamental physical and electronic properties of GeSe such as refractive index, dielectric constant, carrier mobility, lifetime, and diffusion length remain unclear, despite the necessity of this for the design of high-performance GeSe solar cells. In this work, the above basic properties of GeSe are systematically studied by using spectroscopic ellipsometry, space charge limited current measurements, and transient absorption spectroscopy. These comprehensive results provide a solid foundation for the further development of GeSe solar cells.

High-Temperature Formation of a Functional Film at the Cathode/Electrolyte Interface in Lithium–Sulfur Batteries: An In Situ AFM Study

Co-reporter:Shuang-Yan Lang;Yang Shi; Dr. Yu-Guo Guo; Dr. Rui Wen; Dr. Li-Jun Wan

Angewandte Chemie International Edition 2017 Volume 56(Issue 46) pp:14433-14437

Publication Date(Web):2017/11/13

DOI:10.1002/anie.201706979

AbstractLithium–sulfur (Li–S) batteries have been attracting wide attention for their promising high specific capacity. A deep understanding of Li–S interfacial mechanism including the temperature (T) effect is required to meet the demands for battery modification and systematic study. Herein, the interfacial behavior during discharge/charge is investigated at high temperature (HT) of 60 °C in an electrolyte based on lithium bis(fluorosulfonyl) imide (LiFSI). By in situ atomic force microscopy (AFM), dynamic evolution of insoluble Li2S2 and Li2S is studied at the nanoscale. An in situ formed functional film can be directly monitored at 60 °C after Li2S nucleation. It retards side reactions and facilitates interfacial redox. The insight into the interfacial processes at HT provides direct evidence of the existence of the film and reveals its dynamic behavior, providing a new avenue for electrolyte design and performance enhancement.

Ionic interaction-induced assemblies of bimolecular “chessboard” structures

Co-reporter:Zhen-Feng Cai;Ting Chen;Jing-Ying Gu;Dong Wang

Chemical Communications 2017 vol. 53(Issue 65) pp:9129-9132

Publication Date(Web):2017/08/10

DOI:10.1039/C7CC03625F

Here we applied ionic interactions as the driving force to fabricate well-ordered bicomponent assemblies by using two porphyrin ions equipped with oppositely-charged groups. Two kinds of bimolecular chessboard structures were successfully constructed on Au(111) and investigated by scanning tunneling microscopy (STM).

Designed synthesis of SnO2–C hollow microspheres as an anode material for lithium-ion batteries

Co-reporter:Lin-Lin Hu;Li-Ping Yang;Dong Zhang;Xian-Sen Tao;Chen Zeng;An-Min Cao

Chemical Communications 2017 vol. 53(Issue 81) pp:11189-11192

Publication Date(Web):2017/10/10

DOI:10.1039/C7CC05747D

We report a simple and facile synthetic protocol to prepare an SnO2–C hollow composite, which shows improved battery performance when used as an anode material in lithium ion batteries.

Controlled formation of uniform nanoshells of manganese oxide and their potential in lithium ion batteries

Co-reporter:Xiao-Chan Liu;Jun-Yu Piao;De-Shan Bin;Tian-Qi Zhang;Shu-Yi Duan;Zi-Xiao Wu;An-Min Cao

Chemical Communications 2017 vol. 53(Issue 19) pp:2846-2849

Publication Date(Web):2017/03/02

DOI:10.1039/C7CC00284J

Uniform nanoshells of manganese oxides have been successfully prepared by controlling their growth kinetics in solution. The prepared manganese oxides show promising electrochemical performance when used as an anode material in lithium ion batteries.

Controlled synthesis of hierarchically-structured MnCo2O4 and its potential as a high performance anode material

Co-reporter:Zixiao Wu;Fuhai Li;Yonggang Sun;Deshan Bin;Junyu Piao

Science China Chemistry 2017 Volume 60( Issue 9) pp:1180-1186

Publication Date(Web):03 July 2017

DOI:10.1007/s11426-017-9064-9

To satisfy the upsurging demand for energy storage in modern society, anode materials which can deliver high capacity have been intensively researched for the next generation lithium ion batteries. Typically, the binary MnCo2O4 with a characteristic coupled metal cations showed promising potential due to its high theoretical capacity and low cost. Here, by means of a well-designed synthesis control, we demonstrated a scalable process to achieve a hierarchical structure of MnCo2O4, which existed as uniform microspheres with embedded mesopores, showing favorable structural characters for high performance during a fast charge/discharge process. Our synthesis highlighted the importance of sodium salicylate as an essential additive to control the precipitation of the two involved metal cations. It was proved that a dual role was played sodium salicylate which cannot only facilitate the formation of microspheric shape, but also act as an effective precursor for the creation of inner mesopores. We confirmed that the hierarchically-structured MnCo2O4 showed outstanding performance when it was tested as an anode material in lithium ion batteries as revealed by its extraordinary cycling stability and high rate capability.

Template synthesis of imine-based covalent organic framework core-shell structure and hollow sphere: a case of COFTTA-DHTA

Co-reporter:Bing Sun;Dong Wang;Lijun Wan

Science China Chemistry 2017 Volume 60( Issue 8) pp:1098-1102

Publication Date(Web):05 July 2017

DOI:10.1007/s11426-017-9071-0

Controllably synthesizing well-dispersed covalent organic frameworks (COFs) with uniform both morphology and size is still a challenge. Herein, we report the template-directed synthesis of COFTTA-DHTA-based core-shell hybrids under solvothermal conditions by using amino-functionalized SiO2 microspheres as templates coupled with stepwise addition of initial monomer molecules. The modified amino groups on the surfaces of SiO2 templates play an important role in the formation of well-defined NH2-f-SiO2@COFTTA-DHTA core-shell hybrids. COFTTA-DHTA hollow spheres can be obtained by etching SiO2 cores of NH2-f-SiO2@COFTTA-DHTA. Both the NH2-f-SiO2@COFTTA-DHTA and COFTTA-DHTA hollow spheres possess the well-defined morphology, high crystallinity and porosity, excellent dispersion property and high chemical stability. The template synthesis method demonstrated in this work provides a general method for the shape-controlled synthesis of COF-based materials, which is important for the further applications in the fields such as energy storage, drug delivery and catalysis.

The intramolecular H-bonding effect on the growth and stability of Schiff-base surface covalent organic frameworks

Co-reporter:Yi-Ping Mo;Xuan-He Liu;Bing Sun;Hui-Juan Yan;Dong Wang

Physical Chemistry Chemical Physics 2017 vol. 19(Issue 1) pp:539-543

Publication Date(Web):2016/12/21

DOI:10.1039/C6CP06894D

The introduction of intramolecular H-bonding by adding –OH functionalities adjacent to the Schiff base centers is considered to be a useful strategy to enhance the stability and crystallinity of bulk covalent organic frameworks (COFs). However, the influence of intramolecular H-bonding on the synthesis of surface COFs (SCOFs) have been barely explored. Herein, SCOFs based on the Schiff-base reaction between 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehydes with symmetry or asymmetrically substituted hydroxyl functional groups are designed. In the absence of a solvent, hydroxyl substituents can be easily oxidized; thus argon protection is required to obtain high-quality SCOFs. Besides, an extended network with uniform pores can be achieved in spite of the symmetry of substituents. Both experimental results and theoretical calculations show that the influence of intramolecular hydrogen bonding on surface synthesis is not as important as that in bulk phase synthesis because the substrate itself can lead to the complanation of adsorbed molecules. The existence of intramolecular H-bonding can enhance the stability of the network in both acid and alkali environments.

Research progress regarding Si-based anode materials towards practical application in high energy density Li-ion batteries

Co-reporter:Jin-Yi Li;Quan Xu;Ge Li;Ya-Xia Yin;Yu-Guo Guo

Materials Chemistry Frontiers 2017 vol. 1(Issue 9) pp:1691-1708

Publication Date(Web):2017/08/23

DOI:10.1039/C6QM00302H

Silicon has been considered as one of the most promising high-capacity anode materials because of its environmentally friendly character, natural abundance, and attractive operating voltage. However, successful implementation of Si-based anodes in Li-ion batteries is seriously hindered by their huge volume variation and low electric conductivity. The rational design of Si and effective combination of nanosized Si with carbonaceous materials represent the most effective approaches to overcome the challenges towards practical application of Si-based anodes. In this review, the mechanisms of Li–Si alloying and cell failure are briefly analyzed to comprehend the inherent impediments of Si-based anodes. Furthermore, nano-structured Si materials are summarized and nano/micro-structured Si/C and SiOx/C composites with 3D conductive networks and stable interfaces are discussed in detail. Accessory battery components that influence electrochemical performance are also reviewed. As for practical application, full batteries with Si-based anodes are discussed. Finally, the key aspects of Si-based materials are emphasized and prospective strategies for promoting the practical applications of Si-based anodes in high energy density Li-ion batteries are proposed.

Facile Synthesis of Mo2C Nanocrystals Embedded in Nanoporous Carbon Network for Efficient Hydrogen Evolution

Co-reporter:Yuyun Chen;Yun Zhang;Yuling Ma;Tang Tang;Zhihui Dai;Jinsong Hu;Lijun Wan

Chinese Journal of Chemistry 2017 Volume 35(Issue 6) pp:911-917

Publication Date(Web):2017/06/01

DOI:10.1002/cjoc.201600790

AbstractExploring facile and easily-scalable methods for synthesizing earth-abundant, cost-effective and efficient hydrogen evolution reaction (HER) electrocatalysts is essential for the mass production of hydrogen as a clean and sustainable energy carrier. We report here a simple strategy to produce Mo2C nanocrystals embedded in carbon network (Mo2C@C) by the direct pyrolysis of ammonium molybdate and polyvinylpyrrolidone (PVP). It is found that PVP can be effectively used as a single source to form carbides and carbon network. The long polymer chain and coordinating capability with transition metal of PVP make it possible to form connected porous carbon network and well-dispersed Mo2C nanocrystals in several nanometers. The carbonization of PVP not only effectively in-situ prevents the aggregation of Mo2C nanocrystals during their formation, but also provides conductive porous matrix. As a result, the Mo2C@C composite exhibits the superior electrocatalytic performance for HER, which can be ascribed to the large number of active sites from plenty of small Mo2C nanocrystals and the efficient mass and electron transport network from carbon matrix. This strategy may inspire the exploration of cost-effective functional polymer as single source for both carbon precursor and nanostructure-directed reagent to mass-produce well-defined metal carbides nanostructures embedded in porous carbon network for energy applications.

General Space-Confined On-Substrate Fabrication of Thickness-Adjustable Hybrid Perovskite Single-Crystalline Thin Films

Co-reporter:Yao-Xuan Chen, Qian-Qing Ge, Yang Shi, Jie Liu, Ding-Jiang Xue, Jing-Yuan Ma, Jie Ding, Hui-Juan Yan, Jin-Song HuLi-Jun Wan

Journal of the American Chemical Society 2016 Volume 138(Issue 50) pp:16196-16199

Publication Date(Web):November 27, 2016

DOI:10.1021/jacs.6b09388

Organic–inorganic hybrid perovskite single-crystalline thin films (SCTFs) are promising for enhancing photoelectric device performance due to high carrier mobility, long diffusion length, and carrier lifetime. However, bulk perovskite single crystals available today are not suitable for practical device application due to the unfavorable thickness. Herein, we report a facile space-confined solution-processed strategy to on-substrate grow various hybrid perovskite SCTFs in a size of submillimeter with adjustable thicknesses from nano- to micrometers. These SCTFs exhibit photoelectric properties comparable to bulk single crystals with low defect density and good air stability. The clear thickness-dependent colors allow fast visual selection of SCTFs with a suitable thickness for specific device application. The present substrate-independent growth of perovskite SCTFs opens up opportunities for on-chip fabrication of diverse high-performance devices.

GeSe Thin-Film Solar Cells Fabricated by Self-Regulated Rapid Thermal Sublimation

Co-reporter:Ding-Jiang Xue, Shun-Chang Liu, Chen-Min Dai, Shiyou Chen, Chao He, Lu Zhao, Jin-Song Hu, and Li-Jun Wan

Journal of the American Chemical Society 2016 Volume 139(Issue 2) pp:958-965

Publication Date(Web):December 20, 2016

DOI:10.1021/jacs.6b11705

GeSe has recently emerged as a promising photovoltaic absorber material due to its attractive optical and electrical properties as well as earth-abundant and low-toxic constituent elements. However, no photovoltaic device has been reported based on this material so far, which could be attributed to the inevitable coexistence of phase impurities Ge and GeSe2, leading to detrimental recombination-center defects and seriously degrading the device performance. Here we overcome this issue by introducing a simple and fast (4.8 μm min–1) rapid thermal sublimation (RTS) process designed according to the sublimation feature of the layered structured GeSe. This new method offers a compelling combination of assisting raw material purification to suppress deleterious phase impurities and preventing the formation of detrimental point defects through congruent sublimation of GeSe, thus providing an in situ self-regulated process to fabricate high quality polycrystalline GeSe films. Solar cells fabricated following this process show a power conversion efficiency of 1.48% with good stability. This preliminary efficiency and high stability, combined with the self-regulated RTS process (also extended to the fabrication of other binary IV-VI chalcogenide films, i.e., GeS), demonstrates the great potential of GeSe for thin-film photovoltaic applications.

Click and Patterned Functionalization of Graphene by Diels–Alder Reaction

Co-reporter:Jing Li; Meng Li; Li-Li Zhou; Shuang-Yan Lang; Hai-Yan Lu; Dong Wang; Chuan-Feng Chen

Journal of the American Chemical Society 2016 Volume 138(Issue 24) pp:7448-7451

Publication Date(Web):June 6, 2016

DOI:10.1021/jacs.6b02209

Chemical functionalization is a promising approach to controllably manipulate the characteristics of graphene. Here, we designed cis-dienes, featuring two dihydronaphthalene backbones, to decorate a graphene surface via Diels–Alder (DA) click reaction. The installation of a diene moiety into a nonplanar molecular structure to form cis-conformation enables a rapid (∼5 min) DA reaction between graphene and diene groups. Patterned graphene of sub-micrometer resolution can be obtained by easily soaking poly(methyl methacrylate)-masked graphene in solution of hydroxyl-substituted cis-diene at room temperature. The functionalization degree can be further controlled by carrying out the reaction at higher temperature. The present result gives important insight into the effect of molecular conformation on the graphene functionalization process, and provides an effective and facile method for graphene functionalization.

General Synthetic Strategy for Hollow Hybrid Microspheres through a Progressive Inward Crystallization Process

Co-reporter:Li-Ping Yang; Xi-Jie Lin; Xing Zhang; Wei Zhang; An-Min Cao

Journal of the American Chemical Society 2016 Volume 138(Issue 18) pp:5916-5922

Publication Date(Web):April 20, 2016

DOI:10.1021/jacs.6b00773

Hollow hybrid microspheres have found great potential in different areas, such as drug delivery, nanoreactors, photonics, and lithium-ion batteries. Here, we report a simple and scalable approach to construct high-quality hollow hybrid microspheres through a previously unexplored growth mechanism. Starting from uniform solid microspheres with low crystallinity, we identified that a hollowing process can happen through the progressive inward crystallization process initiated on the particle surface: the gradual encroachment of the crystallization frontline toward the core leads to the depletion of the center and forms the central cavity. We showed that such a synthetic platform was versatile and can be applicable for a large variety of materials. By using the production of Li4Ti5O12–carbon hollow hybrid microspheres as an example, we demonstrated that high-performance anode materials could be achieved through synthesis and structure control. We expect that our findings offer new perspectives in different areas ranging from materials chemistry, energy storage devices, catalysis, to drug delivery.

Understanding the High Activity of Fe–N–C Electrocatalysts in Oxygen Reduction: Fe/Fe3C Nanoparticles Boost the Activity of Fe–Nx

Co-reporter:Wen-Jie Jiang; Lin Gu; Li Li; Yun Zhang; Xing Zhang; Lin-Juan Zhang; Jian-Qiang Wang; Jin-Song Hu; Zidong Wei

Journal of the American Chemical Society 2016 Volume 138(Issue 10) pp:3570-3578

Publication Date(Web):February 23, 2016

DOI:10.1021/jacs.6b00757

Understanding the origin of high activity of Fe–N–C electrocatalysts in oxygen reduction reaction (ORR) is critical but still challenging for developing efficient sustainable nonprecious metal catalysts in fuel cells and metal–air batteries. Herein, we developed a new highly active Fe–N–C ORR catalyst containing Fe–Nx coordination sites and Fe/Fe3C nanocrystals (Fe@C-FeNC), and revealed the origin of its activity by intensively investigating the composition and the structure of the catalyst and their correlations with the electrochemical performance. The detailed analyses unambiguously confirmed the coexistence of Fe/Fe3C nanocrystals and Fe–Nx in the best catalyst. A series of designed experiments disclosed that (1) N-doped carbon substrate, Fe/Fe3C nanocrystals or Fe–Nx themselves did not deliver the high activity; (2) the catalysts with both Fe/Fe3C nanocrystals and Fe–Nx exhibited the high activity; (3) the higher content of Fe–Nx gave the higher activity; (4) the removal of Fe/Fe3C nanocrystals severely degraded the activity; (5) the blocking of Fe–Nx downgraded the activity and the recovery of the blocked Fe–Nx recovered the activity. These facts supported that the high ORR activity of the Fe@C-FeNC electrocatalysts should be ascribed to that Fe/Fe3C nanocrystals boost the activity of Fe–Nx. The coexistence of high content of Fe–Nx and sufficient metallic iron nanoparticles is essential for the high ORR activity. DFT calculation corroborated this conclusion by indicating that the interaction between metallic iron and Fe–N4 coordination structure favored the adsorption of oxygen molecule. These new findings open an avenue for the rational design and bottom-up synthesis of low-cost highly active ORR electrocatalysts.

Influence of N,N-Dimethylformamide Annealing on the Local Electrical Properties of Organometal Halide Perovskite Solar Cells: an Atomic Force Microscopy Investigation

Co-reporter:Jiang-Jun Li, Jing-Yuan Ma, Jin-Song Hu, Dong Wang, and Li-Jun Wan

ACS Applied Materials & Interfaces 2016 Volume 8(Issue 39) pp:26002

Publication Date(Web):September 7, 2016

DOI:10.1021/acsami.6b07647

Organometal halide perovskites have been recognized as a new class of materials for photovoltaic application. Solvent annealing introduced during crystallization of bulk or thin-film materials can improve the performance of perovskite solar cells. Herein, we present Kelvin probe force microscopy and conductive atomic force microscopy (c-AFM) measurements to investigate the local optoelectronic properties of a perovskite film after N,N-dimethylformamide (DMF) annealing. AFM results show that DMF annealing induces recrystallization, yielding a large-size polycrystalline perovskite film. Uniform and higher photocurrent is distributed on the film. However, lower surface potential enhancement and photocurrent are observed at grain boundaries (GBs), illustrating that GBs acting as recombination sites are detrimental to photocurrent transport and collection. Our observation provides a nanoscale understanding of the device performance improvement after DMF annealing.Keywords: c-AFM; GBs; KPFM; perovskite solar cells; solvent annealing

Mitigating Voltage Decay of Li-Rich Cathode Material via Increasing Ni Content for Lithium-Ion Batteries

Co-reporter:Ji-Lei Shi, Jie-Nan Zhang, Min He, Xu-Dong Zhang, Ya-Xia Yin, Hong Li, Yu-Guo Guo, Lin Gu, and Li-Jun Wan

ACS Applied Materials & Interfaces 2016 Volume 8(Issue 31) pp:20138

Publication Date(Web):July 20, 2016

DOI:10.1021/acsami.6b06733

Li-rich layered materials have been considered as the most promising cathode materials for future high-energy-density lithium-ion batteries. However, they suffer from severe voltage decay upon cycling, which hinders their further commercialization. Here, we report a Li-rich layered material 0.5Li2MnO3·0.5LiNi0.8Co0.1Mn0.1O2 with high nickel content, which exhibits much slower voltage decay during long-term cycling compared to conventional Li-rich materials. The voltage decay after 200 cycles is 201 mV. Combining in situ X-ray diffraction (XRD), ex situ XRD, ex situ X-ray photoelectron spectroscopy, and scanning transmission electron microscopy, we demonstrate that nickel ions act as stabilizing ions to inhibit the Jahn–Teller effect of active Mn3+ ions, improving d–p hybridization and supporting the layered structure as a pillar. In addition, nickel ions can migrate between the transition-metal layer and the interlayer, thus avoiding the formation of spinel-like structures and consequently mitigating the voltage decay. Our results provide a simple and effective avenue for developing Li-rich layered materials with mitigated voltage decay and a long lifespan, thereby promoting their further application in lithium-ion batteries with high energy density.Keywords: cathode materials; high-capacity; Li-rich; lithium batteries; voltage decay

Wet Chemistry Synthesis of Multidimensional Nanocarbon–Sulfur Hybrid Materials with Ultrahigh Sulfur Loading for Lithium–Sulfur Batteries

Co-reporter:Wen-Cheng Du, Ya-Xia Yin, Xian-Xiang Zeng, Ji-Lei Shi, Shuai-Feng Zhang, Li-Jun Wan, and Yu-Guo Guo

ACS Applied Materials & Interfaces 2016 Volume 8(Issue 6) pp:3584

Publication Date(Web):September 17, 2015

DOI:10.1021/acsami.5b07468

An optimized nanocarbon–sulfur cathode material with ultrahigh sulfur loading of up to 90 wt % is realized in the form of sulfur nanolayer-coated three-dimensional (3D) conducting network. This 3D nanocarbon–sulfur network combines three different nanocarbons, as follows: zero-dimensional carbon nanoparticle, one-dimensional carbon nanotube, and two-dimensional graphene. This 3D nanocarbon–sulfur network is synthesized by using a method based on soluble chemistry of elemental sulfur and three types of nanocarbons in well-chosen solvents. The resultant sulfur–carbon material shows a high specific capacity of 1115 mA h g–1 at 0.02C and good rate performance of 551 mA h g–1 at 1C based on the mass of sulfur–carbon composite. Good battery performance can be attributed to the homogeneous compositing of sulfur with the 3D hierarchical hybrid nanocarbon networks at nanometer scale, which provides efficient multidimensional transport pathways for electrons and ions. Wet chemical method developed here provides an easy and cost-effective way to prepare sulfur–carbon cathode materials with high sulfur loading for application in high-energy Li–S batteries.Keywords: 3D conducting networks; lithium−sulfur batteries; multidimensional nanocarbons; soluble chemistry; sulfur cathode

Core–shell structured TiO2@polydopamine for highly active visible-light photocatalysis

Co-reporter:Wen-Xin Mao, Xi-Jie Lin, Wei Zhang, Zi-Xiang Chi, Rong-Wen Lyu, An-Min Cao and Li-Jun Wan

Chemical Communications 2016 vol. 52(Issue 44) pp:7122-7125

Publication Date(Web):28 Apr 2016

DOI:10.1039/C6CC02041K

This communication reports that the TiO2@polydopamine nanocomposite with a core–shell structure could be a highly active photocatalyst working under visible light. A very thin layer of polydopamine at around 1 nm was found to be critical for the degradation of Rhodamine B.

The formation of an ordered microporous aluminum-based material mediated by phthalic acid

Co-reporter:Wei Zhang, Jian-Hua Cai, Pei-Pei Huang, Lin-Lin Hu, An-Min Cao and Li-Jun Wan

Chemical Communications 2016 vol. 52(Issue 51) pp:8038-8041

Publication Date(Web):31 May 2016

DOI:10.1039/C6CC01667G

By using phthalic acid as a soft template, we showed that it was possible to prepare a microporous aluminum-based material when the precipitation of Al3+ was properly controlled. We also identified that this microporous aluminum-based material could be promising for the removal of fluoride ions in water treatment.

Controlled formation of uniform CeO2 nanoshells in a buffer solution

Co-reporter:Wei Zhang, Li-Ping Yang, Zi-Xiao Wu, Jun-Yu Piao, An-Min Cao and Li-Jun Wan

Chemical Communications 2016 vol. 52(Issue 7) pp:1420-1423

Publication Date(Web):23 Nov 2015

DOI:10.1039/C5CC08422A

Uniform CeO2 nanoshells were successfully prepared by using buffer solution as a unique growth medium. The application of this methodology to construct a yolk–shell structured Au@CeO2 nanocatalyst shows improved performance for the catalytic CO oxidation.

Fabrication of bilayer tetrathiafulvalene integrated surface covalent organic frameworks

Co-reporter:Wei-Long Dong, Shu-Ying Li, Jie-Yu Yue, Cheng Wang, Dong Wang and Li-Jun Wan

Physical Chemistry Chemical Physics 2016 vol. 18(Issue 26) pp:17356-17359

Publication Date(Web):06 Jun 2016

DOI:10.1039/C6CP01804A

A bilayer covalent organic framework (COF) of TTF-based building blocks was obtained by imine reaction between tetrathiafulvalene tetraaldehyde (4ATTF) and p-phenylenediamine (PPDA). Direct evidence for the eclipsed stacking of bilayer structure via π–π interaction between TTF units is provided by high resolution scanning tunneling microscopy.

Self-assembly of a sulfur-bridged annulene: Substrate effect and donor-acceptor complex

Co-reporter:Zhen-Feng Cai, Jie-Yu Yue, Jing Li, Dong Wang, Wei Xu, Li-Jun Wan

Journal of Electroanalytical Chemistry 2016 Volume 781() pp:20-23

Publication Date(Web):15 November 2016

DOI:10.1016/j.jelechem.2016.09.010

We have studied the self-assembly structure of meso-diphenyltetrathia [22]-annulene [2,1,2,1] (DPTTA) on highly oriented pyrolytic graphite (HOPG), Au(111), and single-layer graphene (SLG) modified Au(111) substrates. High resolution scanning tunneling microscopy (STM) reveals that DPTTA molecules pack into one dimensionally ordered row structure on graphene and HOPG surfaces, while assemble into two dimensional close-packed structure on Au(111) surface. We ascribe this difference to the effect of the substrate. The addition of C60 molecules on these DPTTA modified substrates further reveals that the structural difference in DPTTA adlayer can affect its ability to form donor-acceptor (D-A) hierarchical structure with C60 molecules. The results provide an example of substrate effect in self-assemblies of functional molecules, which is significant for the design of molecular based devices.

Optoeletronic investigation of Cu2ZnSn(S,Se)4 thin-films & Cu2ZnSn(S,Se)4/CdS interface with scanning probe microscopy

Co-reporter:Jiangjun Li;Yugang Zou;Ting Chen;Jinsong Hu;Dong Wang

Science China Chemistry 2016 Volume 59( Issue 2) pp:231-236

Publication Date(Web):2016 February

DOI:10.1007/s11426-015-5444-4

The kesterite-structured semiconductor Cu2ZnSn(S,Se)4 (CZTSSe) is prepared by spin coating a non-hydrazine precursor and annealing at Se atmosphere. Local electrical and optoelectronic properties of the CZTSSe thin-film are explored by Kelvin probe force microscopy and conductive atomic force microscopy. Before and after irradiation, no marked potential bending and very low current flow are observed at GBs, suggesting that GBs behave as a charge recombination site and an obstacle for charge transport. Furthermore, CdS nano-islands are synthesized via successive ionic layer adsorption and reaction (SILAR) method on the surface of CZTSSe. By comparing the work function and current flow change of CZTSSe and CdS in dark and under illumination, we demonstrate photo-induced electrons and holes are separated at the interface of p-n junction and transferred in CdS and CZTSSe, respectively.

Single-Molecule Imaging of Iron-Phthalocyanine-Catalyzed Oxygen Reduction Reaction by in Situ Scanning Tunneling Microscopy

Co-reporter:Jing-Ying Gu, Zhen-Feng Cai, Dong Wang, and Li-Jun Wan

ACS Nano 2016 Volume 10(Issue 9) pp:8746

Publication Date(Web):August 10, 2016

DOI:10.1021/acsnano.6b04281

We report herein an in situ electrochemical scanning tunneling microscopy (ECSTM) investigation of iron-phthalocyanine (FePc)-catalyzed oxygen reduction reaction (ORR). A highly ordered FePc adlayer is revealed on a Au(111) electrode. The center ions in the FePc adlayer show uniform high contrast in an oxygen-saturated electrolyte, which is attributed to the formation of an FePc–O2 complex. In situ STM results reveal the sharp contrast change upon shifting the electrode potential to trigger the ORR. Theoretical simulation has supplied further evidence for the contrast difference of the adsorbed FePc species.Keywords: electrocatalyst; electrochemical scanning tunneling microscopy; metal phthalocyanines; oxygen reduction reaction; single-molecule studies

Enantiomeric Excess-Tuned 2D Structural Transition: From Heterochiral to Homochiral Supramolecular Assemblies

Co-reporter:Shu-Ying Li, Ting Chen, Lin Wang, Bing Sun, Dong Wang, and Li-Jun Wan

Langmuir 2016 Volume 32(Issue 27) pp:6830-6835

Publication Date(Web):June 10, 2016

DOI:10.1021/acs.langmuir.6b01418

Spontaneous resolution of enantiomers is an intriguing and important phenomenon in surface chirality studies. Herein, we report on a two-dimensional (2D) structural transition from the heterochiral to homochiral assembly tuned by changing the enantiomeric excess (ee) of enantiomers in the solution phase. Enantiomers cocrystallize as racemates on the surface when the ee of the R-enantiomer (or S-enantiomer) remains below a critical value, whereas chiral segregation is achieved, and globally homochiral surfaces composed of exclusively one enantiomer are obtained as the critical ee is exceeded. The heterochiral–homochiral transition is ascribed to the formation of energetically unfavored homochiral molecular dimers under the control of the majority-rules principle at high ee values. Such results present an intriguing phenomenon in chiral ordering at surfaces, promising a new enlightenment toward understanding chiral resolution and the evolution of chirality.

Surface Host–Guest Supramolecular Assemblies on Porphyrin-Based Covalent Organic Grids

Co-reporter:Xuan-He Liu

The Journal of Physical Chemistry C 2016 Volume 120(Issue 29) pp:15753-15757

Publication Date(Web):February 9, 2016

DOI:10.1021/acs.jpcc.5b11322

The design and construction of stable porous networks featuring tunable cavities for selective guest inclusion remains a great challenge in construction of functional miniature devices. Herein we report on construction and guest inclusion of stable 2D porphyrin-based molecular square grids connected by imine bonds showing crystalline pattern with periodic square cavities. Diperylene diimides molecules can be decorated into the square pores of the porphyrin-based molecular template on HOPG surfaces. The periodicity control over the covalent molecular grid and thus that of guest molecules is demonstrated by changing the building block. The preparation of robust host–guest systems may facilitate the fabrication of molecular miniature devices with designable properties.

Electrochemical (De)Lithiation of 1D Sulfur Chains in Li–S Batteries: A Model System Study

Co-reporter:Chun-Peng Yang; Ya-Xia Yin; Yu-Guo Guo

Journal of the American Chemical Society 2015 Volume 137(Issue 6) pp:2215-2218

Publication Date(Web):February 4, 2015

DOI:10.1021/ja513009v

In contrast to the extensive studies of the electrochemical behavior of conventional cyclic S8 molecules in Li–S batteries, there has been hardly any investigation of the electrochemistry of S chains. Here we use S chains encapsulated in single- and double-walled carbon nanotubes as a model system and report the electrochemical behavior of 1D S chains in Li–S batteries. An electrochemical test shows that S chains have high electrochemical activity during lithiation and extinctive electrochemistry compared with conventional S8. The confined steric effect provides Li+ solid-phase diffusion access to insert/egress reactions with S chains. During lithiation, the long S chains spontaneously become short chains, which show higher discharge plateaus and better kinetics. The unique electrochemistry of S chains supplements the existing knowledge of the S cathode mechanism and provides avenues for rational design of S cathode materials in Li–S batteries.

Solvent-Induced Oriented Attachment Growth of Air-Stable Phase-Pure Pyrite FeS2 Nanocrystals

Co-reporter:Bin-Bin Yu; Xing Zhang; Yan Jiang; Jie Liu; Lin Gu; Jin-Song Hu

Journal of the American Chemical Society 2015 Volume 137(Issue 6) pp:2211-2214

Publication Date(Web):February 3, 2015

DOI:10.1021/ja512979y

We report here the selective synthesis of air-stable phase-pure pyrite FeS2 nanocubes, spheroidal nanocrystals, and microspheres by solvent-induced oriented attachment (OA). It was found that the solvents could control the OA process and thus the morphologies of the products. Solvent exchange experiments and detailed Raman analysis revealed that 1-octanol contributed to the long-term stability of these pyrite nanomaterials.

Formation of Halogen Bond-Based 2D Supramolecular Assemblies by Electric Manipulation

Co-reporter:Qing-Na Zheng; Xuan-He Liu; Ting Chen; Hui-Juan Yan; Timothy Cook; Dong Wang; Peter J. Stang

Journal of the American Chemical Society 2015 Volume 137(Issue 19) pp:6128-6131

Publication Date(Web):May 7, 2015

DOI:10.1021/jacs.5b02206

Halogen bonding has attracted much attention recently as an important driving force for supramolecular assembly and crystal engineering. Herein, we demonstrate for the first time the formation of a halogen bond-based open porous network on a graphite surface using ethynylpyridine and aryl-halide based building blocks. We found that the electrical stimuli of a scanning tunneling microscopy (STM) tip can induce the formation of a binary supramolecular structure on the basis of halogen bond formation between terminal pyridyl groups and perfluoro-iodobenzene. This electrical manipulation method can be applied to engineer a series of linear or porous structures by selecting halogen bond donor and acceptor fragments with different symmetries, as the directional interactions ultimately determine the structural outcome.

Insight into the Effect of Oxygen Vacancy Concentration on the Catalytic Performance of MnO2

Co-reporter:Li Li, Xianghong Feng, Yao Nie, Siguo Chen, Feng Shi, Kun Xiong, Wei Ding, Xueqiang Qi, Jinsong Hu, Zidong Wei, Li-Jun Wan, and Meirong Xia

ACS Catalysis 2015 Volume 5(Issue 8) pp:4825

Publication Date(Web):July 7, 2015

DOI:10.1021/acscatal.5b00320

Oxygen vacancies (OVs) are important for changing the geometric and electronic structures as well as the chemical properties of MnO2. In this study, we performed a DFT+U calculation on the electronic structure and catalytic performance of a β-MnO2 catalyst for the oxygen reduction reaction (ORR) with different numbers and extents of OVs. Comparing those results with the experimental XRD analysis, we determined that OVs produce a new crystalline phase of β-MnO2. Changes in the electronic structure (Bader charges, band structure, partial density of states, local density of states, and frontier molecular orbital), proton insertion, and oxygen adsorption in β-MnO2 (110) were investigated as a function of the bulk OVs. The results show that a moderate concentration of bulk OVs reduced the band gap, increased the Fermi and HOMO levels of the MnO2 (or MnOOH), and elongated the O–O bond of the adsorbed O2 and coadsorbed O2 with H. These changes substantially increase the conductivity of MnO2 for the catalysis of ORR. However, an excessively high concentration of OVs in β-MnO2 (110) will work against the catalytic enhancement of MnO2 for ORR. The DFT+U calculation reveals that a moderate concentration of OVs induced a large overlap of the surface Mn dz2 orbitals, thus introducing an extra donor level at the bottom of the conductive band, which increased the conductivity of β-MnO2 (110). Such a curvilinear change of the catalytic activity and electronic structure as a function of the oxygen vacancy concentration suggests that the β-MnO2 with moderate concentration OVs exhibits the highest conductivity and catalytic activity for ORR.Keywords: catalytic activity; DFT; oxygen reduction reaction; oxygen vacancy; β-MnO2

Physical vapor deposition of amorphous MoS2 nanosheet arrays on carbon cloth for highly reproducible large-area electrocatalysts for the hydrogen evolution reaction

Co-reporter:Xing Zhang, Yun Zhang, Bin-Bin Yu, Xing-Liang Yin, Wen-Jie Jiang, Yan Jiang, Jin-Song Hu and Li-Jun Wan

Journal of Materials Chemistry A 2015 vol. 3(Issue 38) pp:19277-19281

Publication Date(Web):25 Aug 2015

DOI:10.1039/C5TA05793K

Molybdenum sulfide materials have been shown to be promising non-precious metal catalysts for the hydrogen evolution reaction (HER). This work reports a facile and scalable preparation method for amorphous MoS2 nanosheet arrays directly deposited on carbon cloth (a-MoS2 NA/CC) using a highly reproducible physical vapor deposition (PVD) approach. As a result of the three-dimensional nanostructure of the catalyst, the amorphous nature and the abundant exposed edge sites of MoS2, the a-MoS2 NA/CC composite exhibited superior catalytic activity and stability for the HER in acidic solutions.

Facile growth of centimeter-sized single-crystal graphene on copper foil at atmospheric pressure

Co-reporter:Jing Li, Xuan-Yun Wang, Xing-Rui Liu, Zhi Jin, Dong Wang and Li-Jun Wan

Journal of Materials Chemistry A 2015 vol. 3(Issue 15) pp:3530-3535

Publication Date(Web):18 Feb 2015

DOI:10.1039/C5TC00235D

By mildly oxidizing Cu foil and slowing down the total gas flow rate, we develop an easily repeatable atmospheric growth method to grow single-crystal graphene of centimeter-size. The graphene edge, which is different from the previously reported straight edge, is connected by a series of graphene-corners. The graphene-corner, ranging between 100° and 110°, is formed by a zig-zag edge and a mix edge. The oxidation of Cu crystal boundaries results in the rearrangement of active Cu sites for graphene nucleation, thus suppressing graphene nucleation density.

Core–shell structured Ce2S3@ZnO and its potential as a pigment

Co-reporter:Wen-Xin Mao, Wei Zhang, Zi-Xiang Chi, Rong-Wen Lu, An-Min Cao and Li-Jun Wan

Journal of Materials Chemistry A 2015 vol. 3(Issue 5) pp:2176-2180

Publication Date(Web):26 Nov 2014

DOI:10.1039/C4TA05797J

The potential use of cerium selenide (Ce2S3) as a non-toxic pigment has long been plagued by its release of hydrogen sulfide (H2S). Here, it is shown that a uniform nanoshell of zinc oxide (ZnO) can effectively eliminate the released H2S and also improve the thermal stability of Ce2S3. Through a series of investigations, a 40 nm thick ZnO surface coating layer was found to provide full protection for the Ce2S3 core, and this thickness is best for eliminating the release of H2S. Such a core–shell configuration has great potential for real applications of Ce2S3 as an odorless and non-toxic inorganic pigment.

Unexpected functions of oxygen in a chemical vapor deposition atmosphere to regulate graphene growth modes

Co-reporter:Jing Li, Dong Wang and Li-Jun Wan

Chemical Communications 2015 vol. 51(Issue 85) pp:15486-15489

Publication Date(Web):26 Aug 2015

DOI:10.1039/C5CC06073G

Herein, by controlling the oxygen concentration in a graphene growth process, we reveal that the ppm grade of oxygen in the graphene growth atmosphere can tune the graphene growth modes of multilayer growth and graphene etching fragments.

In situ encapsulation of Pd inside the MCM-41 channel

Co-reporter:Xi-Jie Lin, Ai-Zhi Zhong, Yong-Bin Sun, Xing Zhang, Wei-Guo Song, Rong-Wen Lu, An-Min Cao and Li-Jun Wan

Chemical Communications 2015 vol. 51(Issue 35) pp:7482-7485

Publication Date(Web):24 Mar 2015

DOI:10.1039/C5CC00300H

Pd nanoparticles were successfully introduced into the channels of mesoporous silica MCM-41 with their dispersion well-tuned. We identified the dual role played by CTAB, which was critical for both the micelle template and Pd grafting, leading to the formation of a highly active Pd–MCM-41 nanocomposite for catalysing the Suzuki reaction.

Controlled formation of core–shell structures with uniform AlPO4 nanoshells

Co-reporter:Fen-Li Yang, Wei Zhang, Zi-Xiang Chi, Fu-Quan Cheng, Ji-Tao Chen, An-Min Cao and Li-Jun Wan

Chemical Communications 2015 vol. 51(Issue 14) pp:2943-2945

Publication Date(Web):09 Jan 2015

DOI:10.1039/C4CC09924A

Uniform AlPO4 nanoshells are successfully achieved on different core materials by controlling their formation kinetics in solution. The application of this coating protocol to LiCoO2 shows an obvious improvement in its battery performance.

Microscopic Investigation of Grain Boundaries in Organolead Halide Perovskite Solar Cells

Co-reporter:Jiang-Jun Li, Jing-Yuan Ma, Qian-Qing Ge, Jin-Song Hu, Dong Wang, and Li-Jun Wan

ACS Applied Materials & Interfaces 2015 Volume 7(Issue 51) pp:28518

Publication Date(Web):December 3, 2015

DOI:10.1021/acsami.5b09801

Grain boundaries (GBs) play an important role in organic–inorganic halide perovskite solar cells, which have generally been recognized as a new class of materials for photovoltaic applications. To definitely understand the electrical structure and behavior of GBs, here we present Kelvin probe force microscopy and conductive atomic force microscopy (c-AFM) measurements of both typical and inverted planar organolead halide perovskite solar cells. By comparing the contact potential difference (CPD) of these two devices in the dark and under illumination, we found that a downward band bending exists in GBs that predominantly attract photoinduced electrons. The c-AFM measurements observed that higher photocurrents flow through GBs when a low bias overcomes the barrier created by the band bending, indicating that GBs act as effective charge dissociation interfaces and photocurrent transduction pathways rather than recombination sites.Keywords: c-AFM; CPD; GBs; KPFM; perovskite solar cells; photocurrent

Controlled Formation of Metal@Al2O3 Yolk–Shell Nanostructures with Improved Thermal Stability

Co-reporter:Wei Zhang, Xi-Jie Lin, Yong-Gang Sun, De-Shan Bin, An-Min Cao, and Li-Jun Wan

ACS Applied Materials & Interfaces 2015 Volume 7(Issue 49) pp:27031

Publication Date(Web):November 30, 2015

DOI:10.1021/acsami.5b09791

Yolk–shell structured nanomaterials have shown interesting potential in different areas due to their unique structural configurations. A successful construction of such a hybrid structure relies not only on the preparation of the core materials, but also on the capability to manipulate the outside wall. Typically, for Al2O3, it has been a tough issue in preparing it into a uniform nanoshell, making the use of Al2O3-based yolk–shell structures a challenging but long-awaited task. Here, in benefit of our success in the controlled formation of Al2O3 nanoshell, we demonstrated that yolk–shell structures with metal confined inside a hollow Al2O3 nanosphere could be successfully achieved. Different metals including Au, Pt, Pd have been demonstrated, forming a typical core@void@shell structure. We showed that the key parameters of the yolk–shell structure such as the shell thickness and the cavity size could be readily tuned. Due to the protection of a surrounding Al2O3 shell, the thermal stability of the interior metal nanoparticles could be substantially improved, resulting in promising performance for the catalytic CO oxidation as revealed by our preliminary test on Au@Al2O3.Keywords: Al2O3 coating; catalysis; CO oxidation; thermal stability; yolk−shell structure

Si@Cu@Au AFM tips for tip-enhanced Raman spectrum

Co-reporter:Pei Lu;Jing Li;Dong Wang

Science China Chemistry 2015 Volume 58( Issue 9) pp:1494-1500

Publication Date(Web):2015 September

DOI:10.1007/s11426-015-5353-6

Tip-enhanced Raman spectrum (TERS) is a scanning probe technique for acquiring chemical information at high spatial resolution and with high chemical sensitivity. The sensitivity of TERS with atomic force microscopy (AFM) system is mainly determined by the metalized tips. Here, we report a fabrication protocol for AFM-TERS tips that incorporate a copper (Cu) primer film between a gold (Au) layer and a Si AFM tips. They were fabricated by coating the Si tip with a 2 nm Cu layer prior to adding a 20 nm Au layer. For top illumination TERS experiments, these tips exhibited superior TERS performance relative to that observed for tips coated with Au only. Samples included graphene, thiophenol and brilliant cresyl blue. The results may derive from the surface roughness of the tip apex and a Cu/Au synergism of local surface plasmon resonances.

Substrate Orientation Effect in the On-Surface Synthesis of Tetrathiafulvalene-Integrated Single-Layer Covalent Organic Frameworks

Co-reporter:Wei-long Dong, Lin Wang, Hui-min Ding, Lu Zhao, Dong Wang, Cheng Wang, and Li-Jun Wan

Langmuir 2015 Volume 31(Issue 43) pp:11755-11759

Publication Date(Web):October 15, 2015

DOI:10.1021/acs.langmuir.5b02412

The on-surface reactions of tetrathiafulvalene equipped with four benzaldehyde groups (4ATTF) and ditopic diamine molecules are investigated. 4ATTF tends to form large-scale-ordered rhombus structures when reacted with p-phenylenediamine (PPDA). A longer ditopic diamine molecule, 1,1′-biphenyl-4,4′-diamine dihydrochloride (BPDA), causes the domain size of the regular rhombus structure to decrease and triangular and irregular rhombus structures to appear upon reaction with 4ATTF. However, in the rhombus structures formed by different-length ditopic diamine molecules, the single-layer covalent organic frameworks on the graphite surface preferentially orient in alignment with the underlying HOPG substrate lattice.

Graphene-Like Single-Layered Covalent Organic Frameworks: Synthesis Strategies and Application Prospects

Co-reporter:Xuan-He Liu;Cui-Zhong Guan;Dong Wang

Advanced Materials 2014 Volume 26( Issue 40) pp:6912-6920

Publication Date(Web):

DOI:10.1002/adma.201305317

Two-dimensional (2D) nanomaterials, such as graphene and transition metal chalcogenides, show many interesting dimension-related materials properties. Inspired by the development of 2D inorganic nanomaterials, single-layered covalent organic frameworks (sCOFs), featuring atom-thick sheets and crystalline extended organic structures with covalently bonded building blocks, have attracted great attention in recent years. With their unique graphene-like topological structure and the merit of structural diversity, sCOFs promise to possess novel and designable properties. However, the synthesis of sCOFs with well-defined structures remains a great challenge. Herein, the recent development of the bottom-up synthesis methods of 2D sCOFs, such as thermodynamic equilibrium control methods, growth-kinetics control methods, and surface-assisted covalent polymerization methods, are reviewed. Finally, some of the critical properties and application prospects of these materials are outlined.

A Sandwich-Like Hierarchically Porous Carbon/Graphene Composite as a High-Performance Anode Material for Sodium-Ion Batteries

Co-reporter:Yang Yan;Ya-Xia Yin;Yu-Guo Guo

Advanced Energy Materials 2014 Volume 4( Issue 8) pp:

Publication Date(Web):

DOI:10.1002/aenm.201301584

Direct Probing of the Structure and Electron Transfer of Fullerene/Ferrocene Hybrid on Au(111) Electrodes by in Situ Electrochemical STM

Co-reporter:Ting Chen ; Dong Wang ; Li-Hua Gan ; Yutaka Matsuo ; Jing-Ying Gu ; Hui-Juan Yan ; Eiichi Nakamura

Journal of the American Chemical Society 2014 Volume 136(Issue 8) pp:3184-3191

Publication Date(Web):January 31, 2014

DOI:10.1021/ja411813r

The electron donor–acceptor dyads are an emerging class of materials showing important applications in nonlinear optics, dye-sensitized solar cells, and molecular electronics. Investigation of their structure and electron transfer at the molecular level provides insights into the structure–property relationship and can benefit the design and preparation of electron donor–acceptor dyad materials. Herein, the interface adstructure and electron transfer of buckyferrocene Fe(C60Me5)Cp, a typical electron donor–acceptor dyad, is directly probed using in situ electrochemical scanning tunneling microscopy (STM) combined with theoretical simulations. It is found that the adsorption geometry and assembled structure of Fe(C60Me5)Cp is significantly affected by the electrochemical environments. In 0.1 M HClO4 solution, Fe(C60Me5)Cp forms well-ordered monolayers and multilayers on Au(111) surfaces with molecular dimer as the building block. In 0.1 M NaClO4 solution, typical six-fold symmetric close-packed monolayer with vertically adsorbed Fe(C60Me5)Cp is formed. Upon electrochemical oxidation, the oxidized Fe(C60Me5)Cp shows higher brightness in an STM image, which facilitates the direct visualization of the interfacial electrochemical electron transfer process. Theoretical simulation indicates that the electrode potential-activated, one-electron transfer from Fe(C60Me5)Cp to the electrode leads to the change of the delocalization character of the frontier orbital in the molecule, which is responsible for the STM image contrast change. This result is beneficial for understanding the structure and property of single electron donor–acceptor dyads. It also provides a direct approach to study the electron transfer of electron donor–acceptor compounds at the molecular level.

Photoacoustic Imaging Guided Near-Infrared Photothermal Therapy Using Highly Water-Dispersible Single-Walled Carbon Nanohorns as Theranostic Agents

Co-reporter:Daiqin Chen;Chao Wang;Xin Nie;Shumu Li;Ruimin Li;Mirong Guan;Zhuang Liu;Chunying Chen;Chunru Wang;Chunying Shu;Lijun Wan

Advanced Functional Materials 2014 Volume 24( Issue 42) pp:6621-6628

Publication Date(Web):

DOI:10.1002/adfm.201401560

The poly(maleic anhydride-alt-1-octadecene-poly(ethylene glycol)) (C₁₈PMH-PEG) modified single-walled carbon nanohorns (SWNHs) are designed with high stability and biocompatibility. The as-prepared SWNHs/C₁₈PMH-PEG not only can serve as an excellent photothermal agent but also can be used as a promising photoacoustic imaging (PAI) agent both in vitro and in vivo due to its strong absorption in the near infrared (NIR) region. The PAI result reveals that the SWNHs/C₁₈PMH-PEG possesses ultra long blood circulation time and can significantly be accumulated at the tumor site through the enhanced penetration and retention (EPR) effect. The maximum accumulation of SWNHs/C₁₈PMH-PEG at tumor site could be achieved at the time point of 24 h after intravenous injection, which is considered to be the optimal time for the 808 nm laser treatment. The subsequent photothermal ablation of tumors can be achieved without triggering any side effects. Therefore, a PAI guided PTT platform based on SWNHs is proposed and highlights the potential theranostic application for biomedical uses.

In vitro and in vivo photothermally enhanced chemotherapy by single-walled carbon nanohorns as a drug delivery system

Co-reporter:Daiqin Chen, Chao Wang, Feng Jiang, Zhuang Liu, Chunying Shu and Li-Jun Wan

Journal of Materials Chemistry A 2014 vol. 2(Issue 29) pp:4726-4732

Publication Date(Web):23 Apr 2014

DOI:10.1039/C4TB00249K

Single-walled carbon nanohorns (SWNHs) have exhibited many special advantages in biomedical applications. Herein, doxorubicin-loaded SWNHs (DOX-SWNHs) are prepared and further modified by amphiphilic deoxycholic acid modified-hydropropyl chitosan (DCA-HPCHS) to improve their biocompatibility. The obtained DOX-SWNH/DCA-HPCHS drug delivery system (DDS) possesses high stability in physiological media and excellent photothermal properties when exposed to laser irradiation in the near-infrared (NIR) region, which dramatically enhances the chemotherapy of DOX. Cell viability assays show that the growth of 4T1 cells are remarkably inhibitory under the conditions of incubation with DOX-SWNH/DCA-HPCHS and subsequent exposure to 808 nm laser irradiation to produce mild photothermal heating to 43 °C. Further investigation reveals that the photothermally enhanced chemotherapy derived from a promotion of DOX-SWNH/DCA-HPCHS uptake by the cancer cells rather than a light-triggered release of DOX. DOX-SWNH/DCA-HPCHS in combination with the use of laser irradiation exhibits a much better anticancer effect than the controls. Hence, the DOX-SWNH/DCA-HPCHS as a multifunctional DDS has been proposed and is hopeful for medicinal use in the future.

Accurate surface control of core–shell structured LiMn0.5Fe0.5PO4@C for improved battery performance

Co-reporter:Zi-Xiang Chi, Wei Zhang, Xu-Sheng Wang, Fu-Quan Cheng, Ji-Tao Chen, An-Min Cao and Li-Jun Wan

Journal of Materials Chemistry A 2014 vol. 2(Issue 41) pp:17359-17365

Publication Date(Web):26 Aug 2014

DOI:10.1039/C4TA03739A

Manganese-based mixed polyanion cathodes known as LiMn1−xFexPO4 can show much higher energy density as compared to the well-commercialized product of lithium iron phosphate. However, their much lower electronic conductivity has long plagued their further application. Here, by means of a facile solution-based synthesis route, we are able to introduce a uniform and conformal carbon coating layer onto LiMn1−xFexPO4 nanoparticles. The versatility in the synthesis control endows us with the capability of controlling the shell thickness with one nanometer accuracy, offering an effective way to optimize the battery performance through a systematic shell control. Detailed investigation reveals that the carbon nanoshells not only act as good electronic conducting media, but also contribute to the inhibition of the metal (Mn and Fe) dissolution and reduce the exothermic heat released during cycling. The core–shell structured cathode materials show promising potential for their application in lithium ion batteries as revealed by their high charge–discharge capacity, remarkable thermal stability, and excellent cyclability.

In situ nitrogen-doped nanoporous carbon nanocables as an efficient metal-free catalyst for oxygen reduction reaction

Co-reporter:Wen-Jie Jiang, Jin-Song Hu, Xing Zhang, Yan Jiang, Bin-Bin Yu, Zi-Dong Wei and Li-Jun Wan

Journal of Materials Chemistry A 2014 vol. 2(Issue 26) pp:10154-10160

Publication Date(Web):23 Apr 2014

DOI:10.1039/C4TA01780C

A new N-doped carbon nanomaterial with nanoporous coaxial nanocable structure was designed for achieving the requirements of high nitrogen content, proper nitrogen bonding state, and sufficient electron and mass transportation for an oxygen reduction reaction (ORR) catalyst. The nanoporous sheaths provided more catalytic sites and allowed oxygen and reactants to easily access them for fast mass transfer, whereas carbon nanotube cores provided a three-dimensional conductive network and guaranteed fast electron transfer. As a result, the designed low-cost catalyst exhibited excellent electrocatalytic performance and is one of the most active metal-free ORR catalyst.

Enhanced stability and activity with Pd–O junction formation and electronic structure modification of palladium nanoparticles supported on exfoliated montmorillonite for the oxygen reduction reaction

Co-reporter:W. Ding, M.-R. Xia, Z.-D. Wei, S.-G. Chen, J.-S. Hu, L.-J. Wan, X.-Q. Qi, X.-H. Hu and L. Li

Chemical Communications 2014 vol. 50(Issue 50) pp:6660-6663

Publication Date(Web):02 May 2014

DOI:10.1039/C4CC02180K

Palladium has been the focus of recent research on alternative Pt catalysts for the oxygen reduction reaction (ORR). We show that the activity and stability of Pd toward the ORR can be enhanced by Pd–O-oxide covalent bonding when Pd is supported on exfoliated montmorillonite (ex-MMT) nanoplatelets.

Single Nanowire Electrode Electrochemistry of Silicon Anode by in Situ Atomic Force Microscopy: Solid Electrolyte Interphase Growth and Mechanical Properties

Co-reporter:Xing-Rui Liu, Xin Deng, Ran-Ran Liu, Hui-Juan Yan, Yu-Guo Guo, Dong Wang, and Li-Jun Wan

ACS Applied Materials & Interfaces 2014 Volume 6(Issue 22) pp:20317

Publication Date(Web):November 7, 2014

DOI:10.1021/am505847s

Silicon nanowires (SiNWs) have attracted great attention as promising anode materials for lithium ion batteries (LIBs) on account of their high capacity and improved cyclability compared with bulk silicon. The interface behavior, especially the solid electrolyte interphase (SEI), plays a significant role in the performance and stability of the electrodes. We report herein an in situ single nanowire atomic force microscopy (AFM) method to investigate the interface electrochemistry of silicon nanowire (SiNW) electrode. The morphology and Young’s modulus of the individual SiNW anode surface during the SEI growth were quantitatively tracked. Three distinct stages of the SEI formation on the SiNW anode were observed. On the basis of the potential-dependent morphology and Young’s modulus evolution of SEI, a mixture-packing structural model was proposed for the SEI film on SiNW anode.Keywords: in situ atomic force microscopy (AFM); Li-ion battery; single Si nanowire anode; solid electrolyte interphase (SEI)

Controllable atmospheric pressure growth of mono-layer, bi-layer and tri-layer graphene

Co-reporter:Jing Li, Hengxing Ji, Xing Zhang, Xuanyun Wang, Zhi Jin, Dong Wang and Li-Jun Wan

Chemical Communications 2014 vol. 50(Issue 75) pp:11012-11015

Publication Date(Web):28 Jul 2014

DOI:10.1039/C4CC04928D

Here we report a three-step growth method for high-quality mono-layer, bi-layer and tri-layer graphene with coverage ∼90% at atmospheric pressure. The growth temperature and gas flow rate have been found to be the key factors. This method would be of great importance for the large scale production of graphene with defined thickness.

Optimizing LiFePO4@C Core–Shell Structures via the 3-Aminophenol–Formaldehyde Polymerization for Improved Battery Performance

Co-reporter:Zi-xiang Chi, Wei Zhang, Xu-sheng Wang, Fu-quan Cheng, Ji-tao Chen, An-min Cao, and Li-jun Wan

ACS Applied Materials & Interfaces 2014 Volume 6(Issue 24) pp:22719

Publication Date(Web):December 2, 2014

DOI:10.1021/am506860e

Polyanion-type cathode materials are well-known for their low electronic conductivity; accordingly, the addition of conductive carbon in the cathode materials becomes an indispensable step for their application in lithium ion batteries. To maximize the contribution of carbon, a core–shell structure with a full coverage of carbon should be favorable due to an improved electronic contact between different particles. Here, we report the formation of a uniform carbon nanoshell on a typical cathode material, LiFePO4, with the shell thickness precisely defined via the 3-aminophenol–formaldehyde polymerization process. In addition to the higher discharge capacity and the improved rate capability as expected from the carbon nanoshell, we identified that the core–shell configuration could lead to a much safer cathode material as revealed by the obviously reduced iron dissolution, much less heat released during the cycling, and better cyclability at high temperature.Keywords: carbon coating; cathode materials; core−shell structure; iron dissolution; lithium ion batteries

Optimizing the carbon coating on LiFePO4 for improved battery performance

Co-reporter:Zi-Xiang Chi, Wei Zhang, Fu-Quan Cheng, Ji-Tao Chen, An-Min Cao and Li-Jun Wan

RSC Advances 2014 vol. 4(Issue 15) pp:7795-7798

Publication Date(Web):10 Jan 2014

DOI:10.1039/C3RA47702A

Core–shell structures as LiFePO4@carbon with a continuous and uniform carbon coating were achieved by means of the in situ polymerization of dopamine. Systematic control of the coating layer identified that a 5 nm carbon coating produces the best battery performance. Our results provide conclusive evidence for an optimal carbon coating for polyanion-type cathode materials.

Adlayer structures of thiophene and pyrrole derivatives on Au(111) probed by scanning tunneling microscopy

Co-reporter:Bo Cui, Ting Chen, Hui-Juan Yan, Dong Wang, Li-Jun Wan

Journal of Electroanalytical Chemistry 2014 716() pp: 87-92

Publication Date(Web):

DOI:10.1016/j.jelechem.2013.08.037

Carbon-free Cu2ZnSn(S,Se)4 film prepared via a non-hydrazine route

Co-reporter:YuGang Zou;Jie Liu;Xing Zhang;Yan Jiang;JinSong Hu

Science China Chemistry 2014 Volume 57( Issue 11) pp:1552-1558

Publication Date(Web):2014 November

DOI:10.1007/s11426-014-5145-4

The kesterite Cu2ZnSn(S,Se)4 (CZTSSe) is an ideal candidate for light harvesting materials in earth-abundant low-cost thin-film solar cells (TFSC). Although the solution-based processing is a most promising approach to achieve low-cost solar cells with high power conversion efficiency, the issues of poor crystallinity and carbon residue in CZTSSe thin films are still challenging. Herein, a non-hydrazine solution-based method was reported to fabricate highly crystallized and carbon-free kesterite CZTSSe thin films. Interestingly, it was found that the synthetic atmosphere of metal organic precursors have a dramatic impact on the morphology and crystallinity of CZTSSe films. By optimizing the processing parameters, we were able to obtain a kesterite CZTSSe film composed of compact large crystal grains with trace carbon residues. Also, a viable reactive ion etching (RIE) processing with optimized etching conditions was then developed to successfully eliminate trace carbon residues on the surface of the CZTSSe film.

One-Nanometer-Precision Control of Al2O3 Nanoshells through a Solution-Based Synthesis Route

Co-reporter:Wei Zhang;Zi-Xiang Chi;Wen-Xin Mao; Rong-Wen Lv; An-Min Cao; Li-Jun Wan

Angewandte Chemie International Edition 2014 Volume 53( Issue 47) pp:12776-12780

Publication Date(Web):

DOI:10.1002/anie.201406856

Abstract

Forming uniform metal oxide nanocoatings is a well-known challenge in the construction of core–shell type nanomaterials. Herein, by using buffer solution as a specific reaction medium, we demonstrate the possibility to grow thin nanoshells of metal oxides, typically Al₂O₃, on different kinds of core materials, forming a uniform surface-coating layer with thicknesses achieving one nanometer precision. The application of this methodology for the surface modification of LiCoO₂ shows that a thin nanoshell of Al₂O₃ can be readily tuned on the surface for an optimized battery performance.

Electrostatic-Interaction-Induced Molecular Deposition of a Hybrid Bilayer on Au(111): A Scanning Tunneling Microscopy Study

Co-reporter:Jing-Ying Gu, Ting Chen, Lin Wang, Wei-Long Dong, Hui-Juan Yan, Dong Wang, and Li-Jun Wan

Langmuir 2014 Volume 30(Issue 12) pp:3502-3506

Publication Date(Web):2017-2-22

DOI:10.1021/la500873y

Hybrid bilayers consisting of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and meso-tetra(4-pyridyl)porphine (TPyP) have been successfully constructed on Au(111) and investigated by electrochemical scanning tunneling microscopy (ECSTM). Under the guidance of the electrostatic interaction between negatively charged sulfonate groups and positively charged pyridyl groups, the underlying HPTS arrays act as templates for the deposition of cationic TPyPs, forming two types of TPyP/HPTS complex bilayers. The present work provides a feasible way to fabricate hybrid multilayers on the electrode surface via electrostatic interaction, which has great significance for the design of molecular nanodevices.

Adaptive Reorganization of 2D Molecular Nanoporous Network Induced by Coadsorbed Guest Molecule

Co-reporter:Qing-Na Zheng, Lei Wang, Yu-Wu Zhong, Xuan-He Liu, Ting Chen, Hui-Juan Yan, Dong Wang, Jian-Nian Yao, and Li-Jun Wan

Langmuir 2014 Volume 30(Issue 11) pp:3034-3040

Publication Date(Web):2017-2-22

DOI:10.1021/la5002418

The ordered array of nanovoids in nanoporous networks, such as honeycomb, Kagome, and square, provides a molecular template for the accommodation of “guest molecules”. Compared with the commonly studied guest molecules featuring high symmetry evenly incorporated into the template, guest molecules featuring lower symmetry are rare to report. Herein, we report the formation of a distinct patterned superlattice of guest molecules by selective trapping of guest molecules into the honeycomb network of trimesic acid (TMA). Two distinct surface patterns have been achieved by the guest inclusion induced adaptive reconstruction of a 2D molecular nanoporous network. The honeycomb networks can synergetically tune the arrangement upon inclusion of the guest molecules with different core size but similar peripherals groups, resulting in a trihexagonal Kagome or triangular patterns.

Effect of cations in ionic liquids on the electrochemical performance of lithium-sulfur batteries

Co-reporter:Yang Yan;YaXia Yin;YuGuo Guo

Science China Chemistry 2014 Volume 57( Issue 11) pp:1564-1569

Publication Date(Web):2014 November

DOI:10.1007/s11426-014-5154-3

Lithium-sulfur (Li-S) battery is a promising choice for the next generation of high-energy rechargeable batteries, but its application is impeded by the high dissolution of the polysulfides in commonly used organic electrolyte. Room temperature ionic liquids (RTILs) have been considered as appealing candidates for the electrolytes in Li-S batteries. We investigated the effect of cations in RTILs on the electrochemical performance for Li-S batteries. Ex situ investigation of lithium anode for Li-S batteries indicates that during the discharge/charge process the RTIL with N-methyl-N-propylpyrrolidine cations (P13) can effectively suppress the dissolution of the polysulfides, whereas the RTIL with 1-methyl-3-propyl imidazolium cation (PMIM) barely alleviates the shuttling problem. With 0.5 mol L−1 LiTFSI/P13TFSI as the electrolyte of Li-S battery, the ketjen black/sulfur cathode material exhibits high capacity and remarkable cycling stability, which promise the application of the P13-based RTILs in Li-S batteries.

Bilayer Molecular Assembly at a Solid/Liquid Interface as Triggered by a Mild Electric Field

Co-reporter:Qing-Na Zheng;Xuan-He Liu;Xing-Rui Liu;Ting Chen;Hui-Juan Yan;Yu-Wu Zhong;Dr. Dong Wang;Dr. Li-Jun Wan

Angewandte Chemie International Edition 2014 Volume 53( Issue 49) pp:13395-13399

Publication Date(Web):

DOI:10.1002/anie.201406523

Abstract

The construction of a spatially defined assembly of molecular building blocks, especially in the vertical direction, presents a great challenge for surface molecular engineering. Herein, we demonstrate that an electric field applied between an STM tip and a substrate triggered the formation of a bilayer structure at the solid–liquid interface. In contrast to the typical high electric-field strength (10⁹ V m⁻¹) used to induce structural transitions in supramolecular assemblies, a mild electric field (10⁵ V m⁻¹) triggered the formation of a bilayer structure of a polar molecule on top of a nanoporous network of trimesic acid on graphite. The bilayer structure was transformed into a monolayer kagome structure by changing the polarity of the electric field. This tailored formation and large-scale phase transformation of a molecular assembly in the perpendicular dimension by a mild electric field opens perspectives for the manipulation of surface molecular nanoarchitectures.

On-Surface Synthesis of Single-Layered Two-Dimensional Covalent Organic Frameworks via Solid–Vapor Interface Reactions

Co-reporter:Xuan-He Liu ; Cui-Zhong Guan ; San-Yuan Ding ; Wei Wang ; Hui-Juan Yan ; Dong Wang

Journal of the American Chemical Society 2013 Volume 135(Issue 28) pp:10470-10474

Publication Date(Web):June 21, 2013

DOI:10.1021/ja403464h

Surface covalent organic frameworks (SCOFs), featured by atomic thick sheet with covalently bonded organic building units, are promised to possess unique properties associated with reduced dimensionality, well-defined in-plane structure, and tunable functionality. Although a great deal of effort has been made to obtain SCOFs with different linkages and building blocks via both “top-down” exfoliation and “bottom-up” surface synthesis approaches, the obtained SCOFs generally suffer a low crystallinity, which impedes the understanding of intrinsic properties of the materials. Herein, we demonstrate a self-limiting solid–vapor interface reaction strategy to fabricate highly ordered SCOFs. The coupling reaction is tailored to take place at the solid–vapor interface by introducing one precursor via vaporization to the surface preloaded with the other precursor. Following this strategy, highly ordered honeycomb SCOFs with imine linkage are obtained. The controlled formation of SCOFs in our study shows the possibility of a rational design and synthesis of SCOFs with desired functionality.

Pd-induced Pt(IV) reduction to form Pd@Pt/CNT core@shell catalyst for a more complete oxygen reduction

Co-reporter:Meirong Xia, Ying Liu, Zidong Wei, Siguo Chen, Kun Xiong, Li Li, Wei Ding, Jinsong Hu, Li-Jun Wan, Rong Li and Shahnaz Fatima Alvia

Journal of Materials Chemistry A 2013 vol. 1(Issue 46) pp:14443-14448

Publication Date(Web):27 Sep 2013

DOI:10.1039/C3TA13139D

We describe a facile and controllable process for preparing Pd@Pt/CNT core@shell catalysts for the oxygen reduction reaction (ORR) via Pd-induced Pt(IV) reduction on Pd/CNT. The mass-specific activity for the ORR of the Pd@Pt/CNT catalysts is 7–9 times higher than that of the state-of-the-art Pt/C catalysts, but the yield of H2O2, a harmful species for the stability of catalysts, of the former is only 14.1% of that of the latter. The reason for the enhanced activity and the lower H2O2 yield on the Pd@Pt/CNT catalysts was studied by DFT calculations.

High-safety lithium-sulfur battery with prelithiated Si/C anode and ionic liquid electrolyte

Co-reporter:Yang Yan, Ya-Xia Yin, Sen Xin, Jing Su, Yu-Guo Guo, Li-Jun Wan

Electrochimica Acta 2013 Volume 91() pp:58-61

Publication Date(Web):28 February 2013

DOI:10.1016/j.electacta.2012.12.077

A Li-S battery with safety configuration has been constructed by employing electrochemically prelithiated Si/C microspheres as an anode, S/C composites as a cathode, and a room temperature ionic liquid of n-Methyl-n-Allylpyrrolidinium bis(trifluoromethanesulfonyl)imide (RTIL P1A3TFSI) as an electrolyte. Galvanostatic discharge–charge tests show that the as-assembled Li-S battery could deliver a high discharge specific capacity of 1457 mA h g−1 (based on the sulfur cathode) at 0.1 C, indicating the high Li electroactivity of the system. The reversible capacity is 926.4 mA h g−1 in the first cycle, and could remain as high as 670 mA h g−1 after 50 cycles, revealing the favorable compatibility between the RTIL P1A3TFSI electrolyte and the two electrode materials in the Li-S battery. The as-assembled Li-S battery in the charged state can be used for energy output without activation process by charging. This green rechargeable Li-S battery typically gives an output voltage of 1.5 V per cell, which raises the potential for directly replacing the widely used 1.5 V primary alkaline batteries and dry cells without any change of external circuits of current electronic devices but more rechargeable and powerful.

The structural details and substituent effects on biphenyls adlayers with halogen/pseudohalogen substituents on Au(1 1 1): An STM investigation

Co-reporter:Bo Cui, Hui-Juan Yan, Dong Wang, Li-Jun Wan

Journal of Electroanalytical Chemistry 2013 Volume 688() pp:237-242

Publication Date(Web):1 January 2013

DOI:10.1016/j.jelechem.2012.06.014

The substituent effect on the adsorption behaviors of four halogen/pseudohalogen-terminated biphenyls (X–BP–X, with X = F, Br, I and CN) on a Au(1 1 1) surface in 0.1 M HClO4 solution has been investigated by electrochemical scanning tunneling microscopy (ECSTM) and cyclic voltammetry (CV). All the four molecules could form ordered adlayers at adsorption potentials. From F–BP–F, Br–BP–Br to I–BP–I, the molecular adsorption configuration varies from upright, alternating upright and flat-lying to totally flat-lying. In contrast, a trimer motif connected via CN–Au coordination interaction is found as the building unit for the adlayer of CN–BP–CN on Au(1 1 1) electrode. The adlayer structures and configurations are regulated by the properties of the substituted groups.Graphical abstractHighlights► The adlayers of four halogen/pseudohalogen-terminated biphenyls were investigated. ► From F–BP–F to I–BP–I, the molecular configuration varies from upright to flat-lying. ► NC–BP–CN takes flat-lying configuration on Au(1 1 1) via CN–Au coordination.

Solution Effect on Diazonium-Modified Au(111): Reactions and Structures

Co-reporter:Bo Cui, Jing-Ying Gu, Ting Chen, Hui-Juan Yan, Dong Wang, and Li-Jun Wan

Langmuir 2013 Volume 29(Issue 9) pp:2955-2960

Publication Date(Web):February 15, 2013

DOI:10.1021/la400185e

Surface modifications of a Au(111) electrode with 4-bromobenzenediazonium tetrafluoroborate (BBD) in acetonitrile (ACN) and 0.1 M HClO4 have been characterized by scanning tunneling microscopy (STM). In ACN, STM results reveal the formation of disordered thin organic films. The involvement of the radical as an intermediate is evidenced by the negative effect of radical scavengers on organic thin film formation. In contrast, the 4,4′-dibromobiphenyl monolayer is observed when the aqueous solution is used as a medium to carry out the grafting experiment. The biphenyl compound is considered to be generated by a radical–radical coupling reaction.

pH-Responsive Mechanism of a Deoxycholic Acid and Folate Comodified Chitosan Micelle under Cancerous Environment

Co-reporter:Daiqin Chen, Peng Song, Feng Jiang, Xiangyue Meng, Weiping Sui, Chunying Shu, and Li-Jun Wan

The Journal of Physical Chemistry B 2013 Volume 117(Issue 5) pp:1261-1268

Publication Date(Web):January 11, 2013

DOI:10.1021/jp310677p

Smart pH-responsive polymeric micelles have attracted much attention as one of the most promising drug delivery candidates. In this paper, a different substitution of deoxycholic acid (DCA) and folic acid (FA) comodified hydroxypropyl chitosans (HPCHS) were synthesized for doxorubicin (DOX) targeted delivery and controllable release. The results indicate that the DOX-release behavior is pH-responsive and closely related with the grafting proportions of the two hydrophobic ingredients. The pH-responsive mechanism for the optimized (6%DCA)-HPCHS-(0.1%FA) was suggested, resulting from a synergistic effect of gradual hydrolysis of the amido bond and electrostatic repulsion between the subsequently protonated DOX and the amino residue of the chitosan backbone under a cancerous microenvironment. Moreover, the DOX/(6%DCA)-HPCHS-(0.1%FA) micelle as a promising targeted drug delivery system in cancer therapy was evaluated by cell growth inhibition assays and confocal laser microscopy in vitro. The results clearly demonstrate a controlled release of its cargo and promoted curative efficacy of DOX.

LithiumSulfur Batteries: Electrochemistry, Materials, and Prospects

Co-reporter:Dr. Ya-Xia Yin;Sen Xin; Yu-Guo Guo; Li-Jun Wan

Angewandte Chemie International Edition 2013 Volume 52( Issue 50) pp:13186-13200

Publication Date(Web):

DOI:10.1002/anie.201304762

Abstract

With the increasing demand for efficient and economic energy storage, Li-S batteries have become attractive candidates for the next-generation high-energy rechargeable Li batteries because of their high theoretical energy density and cost effectiveness. Starting from a brief history of Li-S batteries, this Review introduces the electrochemistry of Li-S batteries, and discusses issues resulting from the electrochemistry, such as the electroactivity and the polysulfide dissolution. To address these critical issues, recent advances in Li-S batteries are summarized, including the S cathode, Li anode, electrolyte, and new designs of Li-S batteries with a metallic Li-free anode. Constructing S molecules confined in the conductive microporous carbon materials to improve the cyclability of Li-S batteries serves as a prospective strategy for the industry in the future.

In Situ Scanning Tunneling Microscopy Investigation of Subphthalocyanine and Subnaphthalocyanine Adlayers on a Au(111) Electrode

Co-reporter:Jing-Ying Gu, Bo Cui, Ting Chen, Hui-Juan Yan, Dong Wang, and Li-Jun Wan

Langmuir 2013 Volume 29(Issue 1) pp:264-270

Publication Date(Web):December 10, 2012

DOI:10.1021/la3042742

The adsorption behaviors of subphthalocyanine (SubPc) and subnaphthalocyanine (SubNc) on the Au(111) surface were investigated by electrochemical scanning tunneling microscopy (ECSTM). Two types of ordered adlayer structures of SubPc were observed at 550 mV versus the reversible hydrogen electrode (RHE). All of the SubPc molecules take the Cl-down adsorption configuration on Au(111) in both structures. The ordered adlayers exist in the potential range between 350 and 650 mV. The SubNc molecules adsorb on Au(111) in a less-ordered pattern than the SubPc molecules. The present work provides direct evidence for understanding the potential-controlled adsorption behaviors of SubPc and SubNc on the Au(111) surface.

Hybrid molecular nanostructures with donor-acceptor chains

Co-reporter:Liu Yang;CuiZhong Guan;Wan Yue;JingYi Wu;HuiJuan Yan

Science China Chemistry 2013 Volume 56( Issue 1) pp:124-130

Publication Date(Web):2013 January

DOI:10.1007/s11426-012-4666-y

We have fabricated hybrid molecular chain structures formed by electron acceptor compound 1 and electron donor molecules 2 and 3 at the liquid/solid interface of graphite surface. The structural details of the mono-component and the binary assemblies are revealed by high resolution scanning tunneling microscopy (STM). Compound 1 can form two well-ordered lamellar patterns at different concentrations. In the co-adsorption structures, compounds 2 and 3 can insert into the space between molecular chains of compound 1 and form large area well-ordered nanoscale phase separated lamellar structures. The unit cell parameters for the coassemblies can be “flexibly” adjusted to make the electron donors and acceptors perfectly match along the molecular chains. Scanning tunneling spectroscopy (STS) results indicate that the electronic properties of individual molecular donors and acceptors are preserved in the binary self-assembly. These results provide molecular insight into the nanoscale phase separation of organic electron acceptors and donors on surfaces and are helpful for the fabrication of surface supramolecular structures and molecular devices.

Space-Confinement-Induced Synthesis of Pyridinic- and Pyrrolic-Nitrogen-Doped Graphene for the Catalysis of Oxygen Reduction

Co-reporter:Dr. Wei Ding; Zidong Wei;Dr. Siguo Chen;Dr. Xueqiang Qi;Dr. Tao Yang; Jinsong Hu; Dong Wang; Li-Jun Wan;Dr. Shahnaz Fatima Alvi;Dr. Li Li

Angewandte Chemie International Edition 2013 Volume 52( Issue 45) pp:11755-11759

Publication Date(Web):

DOI:10.1002/anie.201303924

Nanocarbon Networks for Advanced Rechargeable Lithium Batteries

Co-reporter:Sen Xin, Yu-Guo Guo, and Li-Jun Wan

Accounts of Chemical Research 2012 Volume 45(Issue 10) pp:1759

Publication Date(Web):September 6, 2012

DOI:10.1021/ar300094m

Carbon is one of the essential elements in energy storage. In rechargeable lithium batteries, researchers have considered many types of nanostructured carbons, such as carbon nanoparticles, carbon nanotubes, graphene, and nanoporous carbon, as anode materials and, especially, as key components for building advanced composite electrode materials. Nanocarbons can form efficient three-dimensional conducting networks that improve the performance of electrode materials suffering from the limited kinetics of lithium storage. Although the porous structure guarantees a fast migration of Li ions, the nanocarbon network can serve as an effective matrix for dispersing the active materials to prevent them from agglomerating. The nanocarbon network also affords an efficient electron pathway to provide better electrical contacts. Because of their structural stability and flexibility, nanocarbon networks can alleviate the stress and volume changes that occur in active materials during the Li insertion/extraction process. Through the elegant design of hierarchical electrode materials with nanocarbon networks, researchers can improve both the kinetic performance and the structural stability of the electrode material, which leads to optimal battery capacity, cycling stability, and rate capability.This Account summarizes recent progress in the structural design, chemical synthesis, and characterization of the electrochemical properties of nanocarbon networks for Li-ion batteries. In such systems, storage occurs primarily in the non-carbon components, while carbon acts as the conductor and as the structural buffer. We emphasize representative nanocarbon networks including those that use carbon nanotubes and graphene. We discuss the role of carbon in enhancing the performance of various electrode materials in areas such as Li storage, Li ion and electron transport, and structural stability during cycling. We especially highlight the use of graphene to construct the carbon conducting network for alloy anodes, such as Si and Ge, to accelerate electron transport, alleviate volume change, and prevent the agglomeration of active nanoparticles. Finally, we describe the power of nanocarbon networks for the next generation rechargeable lithium batteries, including Li–S, Li–O2, and Li–organic batteries, and provide insights into the design of ideal nanocarbon networks for these devices. In addition, we address the ways in which nanocarbon networks can expand the applications of rechargeable lithium batteries into the emerging fields of stationary energy storage and transportation.

Smaller Sulfur Molecules Promise Better Lithium–Sulfur Batteries

Co-reporter:Sen Xin ; Lin Gu ; Na-Hong Zhao ; Ya-Xia Yin ; Long-Jie Zhou ; Yu-Guo Guo

Journal of the American Chemical Society 2012 Volume 134(Issue 45) pp:18510-18513

Publication Date(Web):October 26, 2012

DOI:10.1021/ja308170k

The lithium–sulfur battery holds a high theoretical energy density, 4–5 times that of today’s lithium-ion batteries, yet its applications have been hindered by poor electronic conductivity of the sulfur cathode and, most importantly, the rapid fading of its capacity due to the formation of soluble polysulfide intermediates (Li2Sn, n = 4–8). Despite numerous efforts concerning this issue, combatting sulfur loss remains one of the greatest challenges. Here we show that this problem can be effectively diminished by controlling the sulfur as smaller allotropes. Metastable small sulfur molecules of S2–4 were synthesized in the confined space of a conductive microporous carbon matrix. The confined S2–4 as a new cathode material can totally avoid the unfavorable transition between the commonly used large S8 and S42–. Li–S batteries based on this concept exhibit unprecedented electrochemical behavior with high specific capacity, good cycling stability, and superior rate capability, which promise a practicable battery with high energy density for applications in portable electronics, electric vehicles, and large-scale energy storage systems.

Nanostructured Polyaniline-Decorated Pt/C@PANI Core–Shell Catalyst with Enhanced Durability and Activity

Co-reporter:Siguo Chen ; Zidong Wei ; XueQiang Qi ; Lichun Dong ; Yu-Guo Guo ; Lijun Wan ; Zhigang Shao ;Li Li

Journal of the American Chemical Society 2012 Volume 134(Issue 32) pp:13252-13255

Publication Date(Web):August 1, 2012

DOI:10.1021/ja306501x

We have designed and synthesized a polyaniline (PANI)-decorated Pt/C@PANI core–shell catalyst that shows enhanced catalyst activity and durability compared with nondecorated Pt/C. The experimental results demonstrate that the activity for the oxygen reduction reaction strongly depends on the thickness of the PANI shell and that the greatest enhancement in catalytic properties occurs at a thickness of 5 nm, followed by 2.5, 0, and 14 nm. Pt/C@PANI also demonstrates significantly improved stability compared with that of the unmodified Pt/C catalyst. The high activity and stability of the Pt/C@PANI catalyst is ascribed to its novel PANI-decorated core–shell structure, which induces both electron delocalization between the Pt d orbitals and the PANI π-conjugated ligand and electron transfer from Pt to PANI. The stable PANI shell also protects the carbon support from direct exposure to the corrosive environment.

Improving the Electrode Performance of Ge through Ge@C Core–Shell Nanoparticles and Graphene Networks

Co-reporter:Ding-Jiang Xue ; Sen Xin ; Yang Yan ; Ke-Cheng Jiang ; Ya-Xia Yin ; Yu-Guo Guo

Journal of the American Chemical Society 2012 Volume 134(Issue 5) pp:2512-2515

Publication Date(Web):January 17, 2012

DOI:10.1021/ja211266m

Germanium is a promising high-capacity anode material for lithium ion batteries, but it usually exhibits poor cycling stability because of its huge volume variation during the lithium uptake and release process. A double protection strategy to improve the electrode performance of Ge through the use of Ge@C core–shell nanostructures and reduced graphene oxide (RGO) networks has been developed. The as-synthesized Ge@C/RGO nanocomposite showed excellent cycling performance and rate capability in comparison with Ge@C nanoparticles when used as an anode material for Li ion batteries, which can be attributed to the electronically conductive and elastic RGO networks in addition to the carbon shells and small particle sizes of Ge. The strategy is simple yet very effective, and because of its versatility, it may be extended to other high-capacity electrode materials with large volume variations and low electrical conductivities.

Rutile-TiO2 Nanocoating for a High-Rate Li4Ti5O12 Anode of a Lithium-Ion Battery

Co-reporter:Yong-Qing Wang ; Lin Gu ; Yu-Guo Guo ; Hong Li ; Xiao-Qing He ; Susumu Tsukimoto ; Yuichi Ikuhara

Journal of the American Chemical Society 2012 Volume 134(Issue 18) pp:7874-7879

Publication Date(Web):April 24, 2012

DOI:10.1021/ja301266w

Well-defined Li4Ti5O12 nanosheets terminated with rutile-TiO2 at the edges were synthesized by a facile solution-based method and revealed directly at atomic resolution by an advanced spherical aberration imaging technique. The rutile-TiO2 terminated Li4Ti5O12 nanosheets show much improved rate capability and specific capacity compared with pure Li4Ti5O12 nanosheets when used as anode materials for lithium ion batteries. The results here give clear evidence of the utility of rutile-TiO2 as a carbon-free coating layer to improve the kinetics of Li4Ti5O12 toward fast lithium insertion/extraction. The carbon-free nanocoating of rutile-TiO2 is highly effective in improving the electrochemical properties of Li4Ti5O12, promising advanced batteries with high volumetric energy density, high surface stability, and long cycle life compared with the commonly used carbon nanocoating in electrode materials.

Wurtzite Cu2ZnSnSe4 nanocrystals for high-performance organic–inorganic hybrid photodetectors

Co-reporter:Jian-Jun Wang, Jin-Song Hu, Yu-Guo Guo and Li-Jun Wan

NPG Asia Materials 2012 4(1) pp:e2

Publication Date(Web):2012-01-01

DOI:10.1038/am.2012.2

Indium-free quaternary chalcogenide, Cu2ZnSnSe4 (CZTSe), has driven much attention for its potential application in photovoltaics and optoelectronics. It is well known that the composition and structure of nanocrystals (NCs) significantly affect their optical and electrical properties. Controllable synthesis of materials with new crystal structures, especially metastable structures, has given impetus to the development of nanomaterials with many new exciting properties and applications. High-quality CZTSe NCs with thermodynamically metastable wurtzite phase and optical band gap of 1.46 eV were herein synthesized via a facile, lost-cost and safe-solution method. The formation mechanism of the wurtzite CZTSe NCs was investigated in detail, which indicates high reaction rate and low surface energy are favorable for the formation of wurtzite structure. The promising application of as-synthesized NCs in photovoltaics and optoelectronics has been demonstrated by the high-performance hybrid photodetector made from CZTSe NCs and P3HT, with an on/off ratio larger than 150.

Hanging Pt hollow nanocrystal assemblies on graphene resulting in an enhanced electrocatalyst

Co-reporter:Yu-Ping Xiao, Shuo Wan, Xing Zhang, Jin-Song Hu, Zi-Dong Wei and Li-Jun Wan

Chemical Communications 2012 vol. 48(Issue 83) pp:10331-10333

Publication Date(Web):17 Aug 2012

DOI:10.1039/C2CC35562K

Pt hollow nanostructures assembled by nanocrystals were in situ grown and hung onto graphene layers to combine the merits from favorable catalyst morphology control and synergetic improvement effect of the graphene support, resulting in a composite with enhanced electrocatalytic performance.

Construction and repair of highly ordered 2D covalent networks by chemical equilibrium regulation

Co-reporter:Cui-Zhong Guan, Dong Wang and Li-Jun Wan

Chemical Communications 2012 vol. 48(Issue 24) pp:2943-2945

Publication Date(Web):14 Dec 2011

DOI:10.1039/C2CC16892H

The construction of well-ordered 2D covalent networks via the dehydration of di-borate aromatic molecules was successfully realized through introducing a small amount of water into a closed reaction system to regulate the chemical equilibrium.

Formation of host–guest structure at an electrified electrode surface: An electrochemical STM investigation

Co-reporter:Liu Yang, Dong Wang, Li-Jun Wan

Electrochemistry Communications 2012 Volume 17() pp:82-84

Publication Date(Web):April 2012

DOI:10.1016/j.elecom.2012.02.010

The co-adsorption structures of 4-nitroaniline (4-NA) and polycyclic aromatic molecules, such as pyrene and perylene, on Au(111) surface have been investigated by cyclic voltammetry (CV) and electrochemical scanning tunneling microscopy (ECSTM). 4-NA molecules can form six-fold symmetry networks with surface chirality. Hydrogen bond plays an important role in the formation of this structure. The hexagonal porous enclosed by triangle and square units can serve as a template for the accommodation of pyrene and perylene. The present result provides direct evidence for the host–guest coassembly process at the solid/liquid interfaces.Highlights► 4-NA molecules can form six-fold symmetry networks with chirality. ► The networks contain hexagonal pores enclosed by triangle and square units. ► The porous networks can accommodate polycyclic aromatic molecules.

Initial solid electrolyte interphase formation process of graphite anode in LiPF6 electrolyte: an in situ ECSTM investigation

Co-reporter:Lin Wang, Xin Deng, Pei-Xia Dai, Yu-Guo Guo, Dong Wang and Li-Jun Wan

Physical Chemistry Chemical Physics 2012 vol. 14(Issue 20) pp:7330-7336

Publication Date(Web):05 Apr 2012

DOI:10.1039/C2CP40595D

Understanding the structure and formation dynamics of the solid electrolyte interphase (SEI) on the electrode/electrolyte interface is of great importance for lithium ion batteries, as the properties of the SEI remarkably affect the performances of lithium ion batteries such as power capabilities, cycling life, and safety issues. Herein, we report an in situ electrochemical scanning tunnelling microscopy (ECSTM) study of the surface morphology changes of a highly oriented pyrolytic graphite (HOPG) anode during initial lithium uptake in 1 M LiPF6 dissolved in the solvents of ethylene carbonate plus dimethyl carbonate. The exfoliation of the graphite originating from the step edge occurs when the potential is more negative than 1.5 V vs. Li+/Li. Within the range from 0.8 to 0.7 V vs. Li+/Li, the growth of clusters on the step edge, the decoration of the terrace with small island-like clusters, and the exfoliation of graphite layers take place on the surface simultaneously. The surface morphology change in the initial lithium uptake process can be recovered when the potential is switched back to 2.0 V. Control experiments indicate that the surface morphology change can be attributed to the electrochemical reduction of solvent molecules. The findings may lead to a better understanding of SEI formation on graphite anodes, optimized electrolyte systems for it, as well as the use of in situ ECSTM for interface studies in lithium ion batteries.

Morphology control and shape evolution in 3D hierarchical superstructures

Co-reporter:AnMin Cao;JinSong Hu;LiJun Wan

Science China Chemistry 2012 Volume 55( Issue 11) pp:2249-2256

Publication Date(Web):2012 November

DOI:10.1007/s11426-012-4726-3

Hierarchical structures, in which structure is generated and controlled simultaneously at different size scales, have attracted increasing attention due to their potentials in both theoretical research and practical applications. In this review, a “non-classical crystallization” mechanism is discussed for their possibilities in morphology control of hierarchically-structured materials. Differently, this crystallization route is not based on the attaching and detaching of monomers as happened in the classical case, but through the self-organization of preformed building blocks as nanosized subunits, whose oriented attachment leads to mesocrystals with favorable morphology and texture. Representative materials including both inorganic and organic crystals are reported with possible mechanisms proposed. Synthetic protocols based on this mechanism provide unique inspirations for materials design and could be applied to morphological and structural control of new materials with optimized functions.

Potential Dependent Adsorption Geometry of 2,5-Dihydroxybenzoic Acid on a Au(111) Surface: An in Situ Electrochemical Scanning Tunneling Microscopy Study

Co-reporter:Pei-Xia Dai, Ting Chen, Dong Wang, and Li-Jun Wan

The Journal of Physical Chemistry C 2012 Volume 116(Issue 10) pp:6208-6214

Publication Date(Web):February 21, 2012

DOI:10.1021/jp210119m

Adsorption and electrochemical behaviors of 2,5-dihydroxybenzoic acid (DHB) at the electrochemical interface of Au(111) electrode and 0.1 M aqueous perchloric acid solution have been studied by cyclic voltammetry and in situ electrochemical scanning tunneling microscopy. Under modulation of the substrate potential, three distinct phases labeled as I, II, and III are observed. DHB molecules take the flat-lying configuration and form the herringbone structure in phase I, which exists at lower potential range. DHB molecules take upstanding configuration and form short-range ordered phase II at higher potential range. A transitional phase consisted of alternately arranged flat-lying and upstanding DHB molecules is disclosed at intermediate potential. The potential induced structural transition can be ascribed to the deprotonation process of carboxylic group and redox reaction of hydroquinone moiety. The present study provides important experiment evidence for understanding the adsorption, redox, and structural transition of hydroquinone molecules on solid electrodes.

Better lithium-ion batteries with nanocable-like electrode materials

Co-reporter:Fei-Fei Cao, Yu-Guo Guo and Li-Jun Wan

Energy & Environmental Science 2011 vol. 4(Issue 5) pp:1634-1642

Publication Date(Web):09 Mar 2011

DOI:10.1039/C0EE00583E

Lithium-ion battery constitutes one of the most popular energy sources which powers current electronic instruments. It is also a promising candidate to be used in future electric devices. To fulfil its potential in future battery market, the better properties of lithium-ion batteries, e.g., higher capacity, better rate performance, are undoubtedly required. The development of nanotechnology has greatly advanced the frontier of lithium-ion battery research. Recently, it was realized that the application of nanocable-like structure in the design of electrodes can significantly improve the properties of lithium-ion batteries. Here we give an overiew of the design, synthesis, and applications of such structures in lithium-ion batteries and highlight some of the latest achievements in this area. It is exciting that the future of lithium-ion batteries is quite bright in view of the high specific capacity, much improved rate performance, as well as superior cycling stability brought by the nanocable-like electrode materials.

Chiral Hierarchical Molecular Nanostructures on Two-Dimensional Surface by Controllable Trinary Self-Assembly

Co-reporter:Jia Liu ; Ting Chen ; Xin Deng ; Dong Wang ; Jian Pei

Journal of the American Chemical Society 2011 Volume 133(Issue 51) pp:21010-21015

Publication Date(Web):November 22, 2011

DOI:10.1021/ja209469d

The bottom-up fabrication of surface hierarchical nanostructures is of great importance for the development of molecular nanostructures for chiral molecular recognition and enantioselective catalysis. Herein, we report the construction of a series of 2D chiral hierarchical structures by trinary molecular self-assembly with copper phthalocyanine (CuPc), 2,3,7,8,12,13-hexahexyloxy-truxenone (TrO23), and 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB). A series of flower-like chiral hierarchical molecular architectures with increased generations are formed, and the details of these structures are investigated by high resolution scanning tunneling microscopy (STM). The flower-like hierarchical molecular architectures could be described by a unified configuration in which the lobe of each architecture is composed of a different number of triangular shape building units (TBUs). The off-axis edge-to-edge packing of TBUs confers the organizational chirality of the hierarchical assemblies. On the other hand, the TBUs can tile the surface in a vertex-sharing configuration, resulting in the expansion of chiral unit cells, which thereby further modulate the periodicity of chiral voids in the multilevel hierarchical assemblies. The formation of desired hierarchical structures could be controlled through tuning the molar ratio of each component in liquid phase. The results are significant for the design and fabrication of multicomponent chiral hierarchical molecular nanostructures.

Bandgap Engineering of Monodispersed Cu2–xSySe1–y Nanocrystals through Chalcogen Ratio and Crystal Structure

Co-reporter:Jian-Jun Wang ; Ding-Jiang Xue ; Yu-Guo Guo ; Jin-Song Hu

Journal of the American Chemical Society 2011 Volume 133(Issue 46) pp:18558-18561

Publication Date(Web):October 24, 2011

DOI:10.1021/ja208043g

Bandgap engineering is important in light-absorption optimization of nanocrystals (NCs) for applications such as highly efficient solar cells. Herein, a facile one-pot method is developed to synthesize monodispersed ternary alloyed copper sulfide selenide (Cu2–xSySe1–y) NCs with tunable composition, structure, and morphology. The energy bandgaps can be tuned with the chalcogen ratio, and the crystal structure of the NCs is found to produce an effect on their bandgap and light absorption. The results are significant in bandgap engineering of semiconductor NCs.

Eco-friendly visible-wavelength photodetectors based on bandgap engineerable nanomaterials

Co-reporter:Jian-Jun Wang, Jin-Song Hu, Yu-Guo Guo and Li-Jun Wan

Journal of Materials Chemistry A 2011 vol. 21(Issue 44) pp:17582-17589

Publication Date(Web):22 Sep 2011

DOI:10.1039/C1JM12173A

The development of visible-wavelength photodetectors based on eco-friendly and bandgap engineerable nanomaterials represents an important and promising direction in photodetector study. This highlight reviewed the recent progress in the design and construction of photodetectors based on the environmentally friendly binary metal chalcogenides and bandgap-tunable ternary or quaternary compounds such as InSe, In2Se3, ZrS2, Sb2Se3, and CuInSe2etc. Most photodetectors exhibit high sensitivity, fast photoresponse and good stability, benefiting from increased carrier mobility or improved carrier separation. We believe that the continuous effort in this direction will produce promising and practicable photodetectors and may open up new insight into the design of controllable photodetectors and their potential applications in new fields.

Donor/acceptor complex of triphenylene and trinitrotoluene on Au(111): a scanning tunneling microscopy study

Co-reporter:Rui Wen, Cun-Ji Yan, Hui-Juan Yan, Ge-Bo Pan and Li-Jun Wan

Chemical Communications 2011 vol. 47(Issue 24) pp:6915-6917

Publication Date(Web):19 May 2011

DOI:10.1039/C1CC11358E

The co-adsorption of trinitrotoluene (TNT), a typical π-electron acceptor, and triphenylene (TP), a typical π-electron donor, on a Au(111) surface was investigated by in situ Electrochemical Scanning Tunneling Microscopy (ECSTM). DFT calculations proved that parallelly stacked and well-overlapped TP and TNT molecules can form Donor–Acceptor dyads through intermolecular π–π charge transfer, which agree well with the experimental results in the present work.

Wet chemical synthesis of Cu/TiO2 nanocomposites with integrated nano-current-collectors as high-rate anode materials in lithium-ion batteries

Co-reporter:Fei-Fei Cao, Sen Xin, Yu-Guo Guo and Li-Jun Wan

Physical Chemistry Chemical Physics 2011 vol. 13(Issue 6) pp:2014-2020

Publication Date(Web):04 Jan 2011

DOI:10.1039/C0CP01119C

Using a soft-template assisted method, well-organized Cu/TiO2 nanoarchitectured electrode materials with copper nanowires as their own current collectors are synthesized by controlled hydrolysis of tetrabutyl titanate in the presence of Cu-based nanowires, and investigated by SEM, TEM, XRD, Raman spectroscopy and electrochemical tests towards lithium storage. Two types of Cu/TiO2 nanocomposites with different TiO2 grain sizes are obtained by using different thermal treatments. The two types of Cu/TiO2 nanocomposites show much enhanced rate performances compared with bare TiO2. A high-rate capability (reversible capacity at 7500 mA g−1 still accounts for 58% of its initial capacity at 50 mA g−1) is observed for the Cu/TiO2 nanocomposite with smaller TiO2 grain size. The improvements can be attributed to the integrated Cu nanowires as mechanical supports and efficient current collectors. A cell made from the Cu/TiO2 nanoarchitectured electrodes exhibits promise as an energy storage device with both high energy and high power densities.

Surface-Confined Conformers and Coassembly-Induced Conformer Resolution

Co-reporter:Cui-Zhong Guan, Ting Chen, Jing-Yi Wu, Qing Chen, Dong Wang, Peter J. Stang, and Li-Jun Wan

Langmuir 2011 Volume 27(Issue 16) pp:9994-9999

Publication Date(Web):July 1, 2011

DOI:10.1021/la202076z

Stereoisomerism is a fundamental chemistry issue and has been intensively investigated because of its importance in organic chemistry, biology, and pharmacology. Molecules with freely rotatable single bonds have many interconvertable conformers. Herein, we report the surface-adsorption-induced conformer resolution by employing azobenzene-3,3-dicarboxylic acid (ADA-33) as a model compound. Two linear assembly phases composed of trans conformers on a highly oriented pyrolytic graphite (HOPG) surface are observed by scanning tunneling microscopy. With the codeposition with 1-octanoic acid (OA), only one trans conformer of ADA-33 can be recognized by OA to form a two-component assembly with alternately arranged ADA-33 and OA stripes, which can be attributed to the epitaxial assembly of ADA-33 and OA on the HOPG surface, and weak hydrogen bonding exists between conformer I and OA molecules. The results are of significance with respect to the discrimination and resolution of conformers on a solid surface and provide molecular insights into the coadsorption assembly on the surface.

In Situ STM Evidence for the Adsorption Geometry of Three N-Heteroaromatic Thiols on Au(111)

Co-reporter:Bo Cui, Ting Chen, Dong Wang, and Li-Jun Wan

Langmuir 2011 Volume 27(Issue 12) pp:7614-7619

Publication Date(Web):May 19, 2011

DOI:10.1021/la201155y

The electrochemical behavior of three heteroaromatic thiols (MBs) (2-mercaptobenzimidazole (MBI), 2-mercaptobenzothiazole (MBT), and 2-mercaptobenzoxazole (MBO)) on a Au(111) surface has been investigated by electrochemical scanning tunneling microscopy (ECSTM) and cyclic voltammetry (CV) in 0.1 M HClO4 solution. All three thiols form oriented molecular cluster lines along the reconstruction line direction at 0.55 V. With the electrode potential shifting negatively, the molecules undergo a disordered–ordered structural transition. Molecularly resolved STM images show that all three molecules form striped adlayers in the desorption region on the Au(111) surface. The different heteroatoms in the heteroaromatic rings result in different electrochemical behavior of the MB self-assembled monolayers (SAMs). MBI, MBT, and MBO are proposed to interact with the substrate via the S–Au bonds from thiol group and the coordination interaction of N, S, and O with the substrate from the heteroaromatic ring, respectively. These results provide direct evidence of the electrochemical behavior and the adlayer structures of MB SAMs on the Au electrode.

Hydrogen Bond Partner Reorganization in the Coadsorption of a Monodendron and Pyridylethynyl Derivatives†

Co-reporter:Xu Zhang, Ting Chen, Hui-Juan Yan, Dong Wang, Qing-Hua Fan, Li-Jun Wan, Koushik Ghosh, Hai-Bo Yang, and Peter J. Stang

Langmuir 2011 Volume 27(Issue 4) pp:1292-1297

Publication Date(Web):November 12, 2010

DOI:10.1021/la1037876

Hydrogen bonds with high selectivity and directionality are significant in harnessing molecules to form 2D supramolecular nanostructures. The competition and reorganization of hydrogen bond partners determine the ultimate molecular assembly and pattern in a 2D supramolecular system. In this study, multicomponent assemblies of a monodendron (5-benzyloxy-isophthalic acid derivative, BIC) and pyridylethynyl derivatives [1,4-bis(4-pyridylethynyl)-2,3-bis-dodecyloxy-benzene (PBPC12) and 1,4-bis(4-pyridylethynyl)-2,3-bis-octadecyloxy-benzene (PBPC18)] have been studied by scanning tunneling microscopy (STM) on a graphite surface. BIC molecules are able to associate with PBPC12 and PBPC18 molecules to induce the rearrangement of hydrogen bond partners and form coassembly structures. Interestingly, BIC acts as a template molecule in the coassembly process, and these multicomponent structures exhibit similar structural features to the assembly structures of BIC itself. The structural details of the coassembled structures are revealed by high-resolution STM images, and their relationship with the original BIC assemblies is discussed. These results provide important insights into the design and fabrication of hydrogen-bond-directed multicomponent molecular nanostructures on solid surfaces.

2D Hexagonal Tilings Based on Triangular and Hexagonal Structural Units in the Self-Assembly of Thiacalix[4]arene Tetrasulfonate on an Au(111) Surface

Co-reporter:Dr. Ting Chen;Dr. Hui-Juan Yan;Xu Zhang; Dong Wang; Li-Jun Wan

Chemistry – An Asian Journal 2011 Volume 6( Issue 7) pp:1811-1816

Publication Date(Web):

DOI:10.1002/asia.201000640

Abstract

The formation of several molecular 2D tilings with long-range periodicity, including the Kagome network, distorted Kagome network, and snub trihexagonal tiling from the adsorption and assembly of thiacalix[4]arene tetrasulfonate (TCAS) at the 0.1 M HClO₄/Au(111) interface has been investigated by electrochemical scanning tunneling microscopy (STM). The internal structures of the tilings have been disclosed by high-resolution STM images. The basic structural motifs, namely, the tiles of these tilings are similar, including triangular units and hexagonal units. Due to the different arrangement of the molecules within the triangular units, tiles with different configurations are formed, which further result in the polymorphism of the 2D tiling. This result is of significance for understanding the formation of 2D tiling as well as the design and construction of molecular self-assembled nanostructures.

Scanning Tunneling Microscopy Investigation of Copper Phthalocyanine and Truxenone Derivative Binary Superstructures on Graphite

Co-reporter:Jia Liu;Dr. Dong Wang;Dr. Jie-Yu Wang;Dr. Jian Pei;Dr. Li-Jun Wan

Chemistry – An Asian Journal 2011 Volume 6( Issue 2) pp:424-429

Publication Date(Web):

DOI:10.1002/asia.201000628

Abstract

The binary self-assembly of copper phthalocyanine (CuPc) and 2,3,7,8,12,13-hexahexyloxy-truxenone (TrO23) at the solid/liquid interface of highly oriented pyrolytic graphite (HOPG) was investigated by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Pseduohexagonal and linear patterned superstructures of CuPc are obtained by co-adsorbing with TrO23. High-resolution STM images reveal the structural details of the arrangement of TrO23 and CuPc in the binary assembly structures. The molecular ratio between CuPc and TrO23 in the adlayer can be modulated by the CuPc concentration in liquid phase. The electronic properties of CuPc and TrO23 in the co-adsorbed self-assembly are investigated by STS. The results presented here are helpful to the design and fabrication of multi-component functional molecular nanostructures.

Shape-Persistent Two-Component 2D Networks with Atomic-Size Tunability

Co-reporter:Jia Liu;Xu Zhang;Dr. Dong Wang;Dr. Jie-Yu Wang;Dr. Jian Pei; Peter J. Stang;Dr. Li-Jun Wan

Chemistry – An Asian Journal 2011 Volume 6( Issue 9) pp:2426-2430

Publication Date(Web):

DOI:10.1002/asia.201100431

Abstract

Over the past few years, two-dimensional (2D) nanoporous networks have attracted great interest as templates for the precise localization and confinement of guest building blocks, such as functional molecules or clusters on the solid surfaces. Herein, a series of two-component molecular networks with a 3-fold symmetry are constructed on graphite using a truxenone derivative and trimesic acid homologues with carboxylic-acid-terminated alkyl chains. The hydrogen-bonding partner-recognition-induced 2D crystallization of alkyl chains makes the flexible alkyl chains act as rigid spacers in the networks to continuously tune the pore size with an accuracy of one carbon atom per step. The two-component networks were found to accommodate and regulate the distribution and aggregation of guest molecules, such as COR and CuPc. This procedure provides a new pathway for the design and fabrication of molecular nanostructures on solid surfaces.

Disorder–Order Transformation of Trithiocyanuric Acid Adlayer on a Au(111) Surface Induced by Electrode Potential

Co-reporter:Ting Chen, Pei-Xia Dai, Jing-Yi Wu, Dong Wang, and Li-Jun Wan

The Journal of Physical Chemistry C 2011 Volume 115(Issue 33) pp:16583-16589

Publication Date(Web):July 25, 2011

DOI:10.1021/jp205077j

Synthesis of Monodispersed Wurtzite Structure CuInSe2 Nanocrystals and Their Application in High-Performance Organic−Inorganic Hybrid Photodetectors

Co-reporter:Jian-Jun Wang ; Yong-Qing Wang ; Fei-Fei Cao ; Yu-Guo Guo

Journal of the American Chemical Society 2010 Volume 132(Issue 35) pp:12218-12221

Publication Date(Web):August 16, 2010

DOI:10.1021/ja1057955

A new facile solution method for the synthesis of high-quality CuInSe2 nanocrystals with monodispersed size and uniform hexagonal shape was developed. A high-performance hybrid photodetector based on a hybrid film of CuInSe2 nanocrystals and poly(3-hexylthiophene) was constructed. The device showed distinct “ON” and “OFF” states with a ratio of >100 in photocurrents responding to outside illumination. The high sensitivity and stability of the hybrid device revealed a broad prospect for use of the hybrid material in light detection and signal magnification for the development of large-area, low-cost, lightweight, and foldable products.

Chiral Kagome Network from Thiacalix[4]arene Tetrasulfonate at the Interface of Aqueous Solution/Au(111) Surface: An in Situ Electrochemical Scanning Tunneling Microscopy Study

Co-reporter:Ting Chen ; Qing Chen ; Xu Zhang ; Dong Wang

Journal of the American Chemical Society 2010 Volume 132(Issue 16) pp:5598-5599

Publication Date(Web):April 5, 2010

DOI:10.1021/ja101598p

A chiral Kagome network was fabricated at an aqueous solution/Au(111) interface by using a complicated stereo supramolecule thiacalix[4]arene tetrasulfonate as a building block. It opens the possibility to construct a 2D nanoporous network by various functional supramolecules and shows potential application in host−guest chemistry as well as chiral resolution.

Symbiotic Coaxial Nanocables: Facile Synthesis and an Efficient and Elegant Morphological Solution to the Lithium Storage Problem

Co-reporter:Fei-Fei Cao, Yu-Guo Guo, Shu-Fa Zheng, Xing-Long Wu, Ling-Yan Jiang, Rong-Rong Bi, Li-Jun Wan and Joachim Maier

Chemistry of Materials 2010 Volume 22(Issue 5) pp:1908

Publication Date(Web):January 22, 2010

DOI:10.1021/cm9036742

Well-organized carbon nanotube (CNT)@TiO2 core/porous-sheath coaxial nanocables are synthesized by controlled hydrolysis of tetrabutyl titanate in the presence of CNTs, and investigated with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electrochemical experiments. The CNT@TiO2 coaxial nanocables show excellent rate capability and cycling performance compared with both pure CNT and pure TiO2 when used as anode materials for lithium-ion batteries (LIBs). Both the specific capacity in the CNT core and that in the TiO2 sheath are much higher than that of the TiO2-free CNT and that of the CNT-free TiO2 sample, respectively. These results demonstrate that the coaxial cable morphology provides a clever solution to the ionic-electronic wiring problem in LIBs as well as the synergism of the two cable wall materials. On one hand, the CNT core provides sufficient electrons for the storage of Li in TiO2 sheath. On the other hand, the CNT itself can also store Li whereby this storage kinetics is, in turn, improved by the presence of the nanoporous TiO2 because the only very thin protection layer on TiO2 (unlike free CNT) enables rapid access of Li-ions from the liquid electrolyte. This fascinating symbiotic behavior and the fact that the cable morphology leads to an efficient use of this symbiosis makes this solution match the requirements of LIBs extremely well.

Substitution effect on the adlayer formation of tetrachloroperylene bisimides on HOPG surface

Co-reporter:Qing Chen, Xu Zhang, Ting Chen, Dong Wang, Hua-Lei Qian, Zhao-Hui Wang, Li-Jun Wan

Surface Science 2010 Volume 604(23–24) pp:2078-2083

Publication Date(Web):November 2010

DOI:10.1016/j.susc.2010.08.022

Di-perylene-3,4,9,10-tetracarboxylic acid bisimides (diPBI) is an n-type graphene molecule with nonplanar conformation. The controllable assembly and molecular adlayer structures of tetrachlorinated diPBI derivatives with different alkyl chains substitutions on highly oriented pyrolytic graphite were studied by scanning tunneling microscopy. When the molecule was substituted by butyl, the formation of multilayer or monolayer can be regulated by the solution concentration. When the molecule was substituted by 2-ethylhexyl, however, it can only form monolayer assembly. The unit cell of 2-ethylhexyl substituted diPBI adlayer was expanded to a rectangular shape compared to that of the butyl substituted diPBI. The steric repulsion of the alkyl chains (straight or branched) substitution is proposed as the key factor to control the adlayer structures of diPBI derivatives. The result is helpful to the design and fabrication of the organic film of chemically synthesized graphene type materials.

Facile Synthesis of Mesoporous TiO2−C Nanosphere as an Improved Anode Material for Superior High Rate 1.5 V Rechargeable Li Ion Batteries Containing LiFePO4−C Cathode

Co-reporter:Fei-Fei Cao, Xing-Long Wu, Sen Xin, Yu-Guo Guo and Li-Jun Wan

The Journal of Physical Chemistry C 2010 Volume 114(Issue 22) pp:10308-10313

Publication Date(Web):May 17, 2010

DOI:10.1021/jp103218u

Well-organized mesoporous TiO2−C nanospheres are manufactured in large scale starting from tetrabutyl titanate (TBT) and glucose in solution, and investigated with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 adsorption−desorption isotherms, and electrochemical experiments. The TiO2−C nanospheres show excellent rate capability and cycling performance for lithium ion batteries. At the extremely high rate of 100 C (discharge/charge within 36 s), the TiO2−C nanosphere can still deliver a specific capacity as high as 96 mA h g−1. Moreover, the as-obtained mesoporous TiO2−C nanosphere can be used as an anode material for a new high rate 1.5 V rechargeable Li ion full cell containing a LiFePO4−C cathode with similar mixed conducting 3D networks. This type of rechargeable battery typically gives an output of 1.5 V per cell, which raises the potential for directly replacing the widely used 1.5 V primary alkaline batteries and dry cells.

Solvent-Controlled 2D Host−Guest (2,7,12-Trihexyloxytruxene/Coronene) Molecular Nanostructures at Organic Liquid/Solid Interface Investigated by Scanning Tunneling Microscopy

Co-reporter:Jia Liu, Xu Zhang, Hui-Juan Yan, Dong Wang, Jie-Yu Wang, Jian Pei and Li-Jun Wan

Langmuir 2010 Volume 26(Issue 11) pp:8195-8200

Publication Date(Web):December 23, 2009

DOI:10.1021/la904568q

The two-dimensional (2D) self-assembled networks of 2,7,12-trihexyloxytruxene (Tr) are shown to accommodate coronene guest molecules on highly oriented pyrolytic graphite (HOPG) surfaces. The host−guest structures are revealed by scanning tunneling microscopy (STM) at liquid/solid interfaces. The effect of solvents on the host−guest structures is intensively investigated in different solvents such as 1,2,4-trichlorobenzene (TCB), 1-phenyloctane, 1-octanol, and tetradecane. In contrast to the similar 2D hexagonal self-assembly of Tr host template on HOPG in different solvents, the formation of host−guest nanostructures of coronene in Tr 2D network strongly depend on the polarity of the solvents. The thermodynamic equilibrium during the host−guest assembly process is discussed, and the solvent−guest interaction is proposed as a main contributor for the observed solvent effect in the 2D host−guest self-assembly process. The results are significant to surface host−guest chemistry and nanopatterning.

Structure and structural transition of chiral domains in oligo(p-phenylenevinylene) assembly investigated by scanning tunneling microscopy

Co-reporter:Qing Chen;Ting Chen;Dong Wang;Hui-Biao Liu;Yu-Liang Li

PNAS 2010 Volume 107 (Issue 7 ) pp:2769-2774

Publication Date(Web):2010-02-16

DOI:10.1073/pnas.1000120107

OPV3-CHO molecules are employed to prepare assembly on highly oriented pyrolytic graphite, and the so-prepared assembly is investigated by scanning tunneling microscopy. In the assembly chiral domains are observed with various structures such as linear and windmill. The chiral structural formation, stability, transition, and possible unification are intensively studied. After thermal annealing, linear structure was the only structure. To achieve a unified assembly with a single structure, an efficient method is proposed by coadsorption of OPV3-CHO with selected molecules. For example, an assembly with side-by-side helix structure is formed by a simple coadsorption of OPV3-CHO with alkyl bromide (CnH2n+1Br, n = 15–18). The experiments by cocrystallization of OPV3-CHO/CnH2n+1X (X = Cl, Br, and I) show the important role of halogen bonding in formation of the uniform structure. The results are significant in understanding the intermolecular noncovalent interactions that dominate the surface structure and chirality.

Engineering of Linear Molecular Nanostructures by a Hydrogen-Bond-Mediated Modular and Flexible Host−Guest Assembly

Co-reporter:Xu Zhang, Ting Chen, Hui-Juan Yan, Dong Wang, Qing-Hua Fan, Li-Jun Wan, Koushik Ghosh, Hai-Bo Yang, and Peter J. Stang

ACS Nano 2010 Volume 4(Issue 10) pp:5685

Publication Date(Web):September 9, 2010

DOI:10.1021/nn101727u

The formation of a desired nanostructure with concomitant patterns and functions is of utmost importance in the field of surface molecular engineering and nanotechnology. We here present a flexible host−guest assembly, which steers the formation of linear molecular nanostructures on surfaces by a hydrogen-bond-mediated assembly process. A linear monodendron molecular template with periodic hydrogen-bond binding sites is shown to accommodate a variety of molecules with pyridylethynyl terminals. The unit cell parameters in the transverse direction of the linear pattern can be tuned from 3.4 to 7.3 nm in response to the packing of the guest molecules with different sizes, shapes, and aggregation number. The introduction of hydrogen-bonding partners into the host template and into guest molecules is responsible for the steering of the linear pattern of guest molecules. The modular approach could greatly facilitate the ordering of guest molecules with desired functional moieties.Keywords: hydrogen bond; molecular template; scanning tunneling microscopy; self-assembly; surface and interface

In Situ Scanning Tunneling Microscopy of Solvent-Dependent Chiral Patterns of 1,4-Di[4-N-(trihydroxymethyl)methyl carbamoylphenyl]-2,5-didodecyloxybenzene Molecular Assembly at a Liquid/Highly Oriented Pyrolytic Graphite Interface

Co-reporter:Ting Chen, Dong Wang, Xu Zhang, Qi-Long Zhou, Rong-Ben Zhang and Li-Jun Wan

The Journal of Physical Chemistry C 2010 Volume 114(Issue 1) pp:533-538

Publication Date(Web):December 3, 2009

DOI:10.1021/jp9089613

Solvent effect on chirality of 1,4-di[4-N-(trihydroxymethyl)methyl carbamoylphenyl]-2,5-didodecyloxybenzene (DTCD) self-assembled adlayer on highly oriented pyrolytic graphite (HOPG) is investigated by in situ scanning tunneling microscopy using tetrahydrofuran (THF), 1-phenyloctane (PO), 1-octanol, and 1,2,4-trichlorobenzene (TCB) as solvent. Different chiral patterns are acquired in these solvents, suggesting that the chiral assembly of DTCD is solvent-dependent. With use of THF or PO as solvent, chiral patterns with windmill-shaped tetramer units are observed. In contrast, a racemic lamellar structure is revealed in 1-octanol. The coadsorption of 1-octanol molecules makes an important contribution to the formation of racemic lamellar structure. A structure transition from racemic lamellar structure to tetramer-based chiral patterns is observed with removal of 1-octanol molecules by thermal annealing. When TCB is used as solvent, a chiral meshy structure is formed at the TCB/HOPG interface. The results reported here demonstrate that solvent can significantly affect the chirality in molecular self-assembly and provide a potential approach to finely tune the chiral molecular architectures on solid surfaces.

Highly Dispersed RuO2 Nanoparticles on Carbon Nanotubes: Facile Synthesis and Enhanced Supercapacitance Performance

Co-reporter:Rong-Rong Bi, Xing-Long Wu, Fei-Fei Cao, Ling-Yan Jiang, Yu-Guo Guo and Li-Jun Wan

The Journal of Physical Chemistry C 2010 Volume 114(Issue 6) pp:2448-2451

Publication Date(Web):January 25, 2010

DOI:10.1021/jp9116563

RuO2/CNT nanocomposites with well-dispersed RuO2 nanoparticles (diameter <2 nm) on the carbon nanotubes’ surface, synthesized through an easy and efficient solution-based method, have been investigated for potential application in electrochemical capacitors (ECs) as electrode materials. The electrochemical results demonstrate that the supporting material of CNT can significantly promote the supercapacitance performance of RuO2. The RuO2 nanoparticles in the composite with a RuO2/CNT mass ratio of 6:7 could achieve a specific capacitance of as high as 953 F g−1. The results also demonstrate that the resulted RuO2/CNT nanocomposites are superior electrode materials for ECs with a high specific capacitance and significantly enhanced high-power and high-energy capabilities as well as improved cycling performance compared with bare RuO2. At a power density of 5000 W kg−1, the RuO2/CNT composite (RuO2/CNT = 6:7 in wt %) can still deliver an energy density of 16.8 Wh kg−1, which is about 5.8 times larger than that of bare RuO2 (2.9 Wh kg−1). The much improved electrochemical performances could be attributed to the dispersive action and good electronic conductivity of CNTs as well as the pinning effect for nanosized RuO2 particles on the CNTs’ surfaces.

Substituent-Dependent Ordering of Adlayer Structures of Fullerene Derivatives Adsorbed on Au(111): A Scanning Tunneling Microscopy Study

Co-reporter:Ting Chen, Ge-Bo Pan, Hui-Juan Yan, Li-Jun Wan, Yutaka Matsuo and Eiichi Nakamura

The Journal of Physical Chemistry C 2010 Volume 114(Issue 7) pp:3170-3174

Publication Date(Web):February 1, 2010

DOI:10.1021/jp9114173

The adsorption of four fullerene derivatives, including Re(C60Me5)(CO)3, Ru(C60Ph5)Cp, C60(C6H4C6H4−COOH)5Me, and C60(C6H4−CC−SiMe2C12H25)5Me, on a Au(111) surface has been investigated by scanning tunneling microscopy (STM) and cyclic voltammetry. High-resolution STM images reveal that Re(C60Me5)(CO)3 forms a well-ordered (2√3 × 2√3)R30° structure. Different from C60 on Au(111), the so-called “in-phase” structure is not found with the attachment of methyl and Re(CO)3 groups. With the increase of substituent size, disordered adlayers have been observed for Ru(C60Ph5)Cp and C60(C6H4C6H4−COOH)5Me. However, the individual molecules could be distinguished in STM images, suggesting that the two molecules interact strongly with the Au(111) surface. When the substituent size is further increased, a multilayered structure is formed for C60(C6H4−CC−SiMe2C12H25)5Me. This is because of molecular aggregation in the bulk solution, which occurs at very low concentration. These results indicate that the structures of fullerene derivatives play an essential role in adlayer formation through adjusting molecule−substrate and molecule−molecule interactions.

Formation and structural transition of molecular self-assembly on solid surface investigated by scanning tunneling microscopy

Co-reporter:Dong Wang, Li-Jun Wan, Chun-Li Bai

Materials Science and Engineering: R: Reports 2010 70(3–6) pp: 169-187

Publication Date(Web):22 November 2010

DOI:10.1016/j.mser.2010.06.016

The spontaneous formation of ordered self-assembly on solid supports is not only an intriguing subject for fundamental surface science study, but also closely related to many emerging technologically important applications, especially in the field of nanotechnology. With the help of scanning tunneling microscopy (STM) at sub-molecular resolution, the detailed structural information within the self-assembled monolayers can be obtained, which allows us to have an insight into how the interplay between the intermolecular weak interactions and the substrate–molecule interactions governs the formation of molecular self-assembly. In this review, the structural transition of self-assembly in response to the subtle differences in the molecular structures and/or the environment change will be presented. The fundamental understanding about the driving force controlling the assembly process promotes the development of various means to tune the structural transition of supramolecular assembly on solid surfaces and fabricate the sophisticated architectures. Finally, some future directions in the field are outlined.

Surface Confined Metallosupramolecular Architectures: Formation and Scanning Tunneling Microscopy Characterization

Co-reporter:Shan-Shan Li, Brian H. Northrop, Qun-Hui Yuan, Li-Jun Wan and Peter J. Stang

Accounts of Chemical Research 2009 Volume 42(Issue 2) pp:249

Publication Date(Web):December 15, 2008

DOI:10.1021/ar800117j

Metallosupramolecular compounds have attracted a great deal of attention over the past two decades largely because of their unique, highly complex structural characteristics and their potential electronic, magnetic, optical, and catalytic properties. These molecules can be prepared with relative ease using coordination-driven self-assembly techniques. In particular, the use of electron-poor square-planar Pt(II) transition metals in conjunction with rigid, electron-rich pyridyl donors has enabled the spontaneous self-assembly of a rich library of 2D metallacyclic and 3D metallacage assemblies via the directional-bonding approach. With this progress in the preparation and characterization of metallosupramolecules, researchers have now turned their attention toward fully exploring and developing their materials properties. Assembling metallosupramolecular compounds on solid supports represents a vitally important step toward developing their materials properties. Surfaces provide a means of uniformly aligning and orienting these highly symmetric metallacycles and metallacages. This uniformity increases the level of coherence between molecules above that which can be achieved in the solution phase and provides a way to integrate adsorbed layers, or adlayers, into a solid-state materials setting. The dynamic nature of kinetically labile Pt(II)−N coordination bonds requires us to adjust deposition and imaging conditions to retain the assemblies’ stability. Toward these aims, we have used scanning tunneling microscopy (STM) to image these adlayers and to understand the factors that govern surface self-assembly and the interactions that influence their structure and stability. This Account describes our efforts to deposit 2D rectangular and square metallacycles and 3D trigonal bipyramidal and chiral trigonal prism metallacages on highly oriented pyrolytic graphite (HOPG) and Au(111) substrates to give intact assemblies and ordered adlayers. We have investigated the effects of varying the size, symmetry, and dimensionality of supramolecular adsorbates, the choice of substrate, the use of a molecular template, and the effects of chirality. Our systematic investigations provide insights into the various adsorbate−adsorbate and substrate−adsorbate interactions that largely determine the architecture of each assembly and affect their performance in a materials setting. Rational control over adlayer formation and structure will greatly enhance the potential of these supramolecules to be used in a variety of applications such as host−guest sensing/diagnostic systems, molecular electronic devices, and heterogeneous stereoselective synthesis and catalysis.

High Performance Photodetectors of Individual InSe Single Crystalline Nanowire

Co-reporter:Jian-Jun Wang ; Fei-Fei Cao ; Lang Jiang ; Yu-Guo Guo ; Wen-Ping Hu

Journal of the American Chemical Society 2009 Volume 131(Issue 43) pp:15602-15603

Publication Date(Web):October 13, 2009

DOI:10.1021/ja9072386

A simple method was introduced to synthesize nanomaterials of a new metal selenide, InSe nanowires (NWs). The NWs had diameters ranging from 60 to 250 nm and lengths from several micrometers to tens of micrometers. The photoresponse characteristics of InSe NWs were investigated by fabricating devices based on an individual NW. With the light irradiation on and off, the current of the device could be switched at “high” and “low” current with the “ON/OFF” ratio as high as 50. Moreover, the high stability of the InSe NWs was demonstrated indicating the bright future of NWs for low cost, ultrahigh density nanometer sized photoelectric devices.

Linear dislocation tunes chirality: STM study of chiral transition and amplification in a molecular assembly on an HOPG surface

Co-reporter:Ting Chen, Qing Chen, Ge-Bo Pan, Li-Jun Wan, Qi-Long Zhou and Rong-Ben Zhang

Chemical Communications 2009 (Issue 19) pp:2649-2651

Publication Date(Web):11 Feb 2009

DOI:10.1039/B817525J

Molecular arrangement and transition in the domain boundary of a chiral two-dimensional assembly is clearly revealed by high-resolution STM images on an HOPG surface and a linear dislocation formed by molecular trimers and located at opposite chiral domains is found to directly reverse the chirality on DTCD self-assembly.

Programmed Fabrication of Bimetallic Nanobarcodes for Miniature Multiplexing Bioanalysis

Co-reporter:Wei-Ming Zhang, Jin-Song Hu, Hai-Tao Ding, Li-Jun Wan and Wei-Guo Song

Analytical Chemistry 2009 Volume 81(Issue 7) pp:2815

Publication Date(Web):February 25, 2009

DOI:10.1021/ac802670q

Nanobarcodes with Morse code patterns are fabricated by a programmed electrochemical deposition process. These bimetallic nanobarcodes are stable and easy to decode using optical or electrical devices. Their discretionally patterned codes offer mass memory capacity for information carriers. They show promising features as probe molecules’ carriers in multiplexing bioanalysis.

Self-assembly and aggregation of melamine and melamine–uric/cyanuric acid investigated by STM and AFM on solid surfaces

Co-reporter:Xu Zhang, Ting Chen, Qing Chen, Ling Wang and Li-Jun Wan

Physical Chemistry Chemical Physics 2009 vol. 11(Issue 35) pp:7708-7712

Publication Date(Web):24 Jun 2009

DOI:10.1039/B907557G

The self-assembly and aggregation of melamine (M), and a mixture of melamine with uric/cyanuric acid (UA/CA) are investigated by performing scanning tunneling microscopy (STM) and atomic force microscopy (AFM) on graphite and mica surfaces at room temperature. Two-dimensional (2D) porous molecular networks and disordered adlayers are found, respectively, in the M and UA–M assembly on graphite. Uniformly dispersed nanoparticles of M and UA–M are found at various concentrations by AFM. Owing to complementary NH⋯O and NH⋯N hydrogen bonds, the CA–M mixture forms 2D densely packed adlayers and nanoscale crystals on graphite and aggregates into three-dimensional (3D) clusters on the surfaces. The size of the cluster is dependent on the molecular concentration. The results provide important information for the self-assembly of triazine compounds and are significant in the study of kidney disease related to melamine.

One Solvent Induces a Series of Structural Transitions in Monodendron Molecular Self-Assembly from Lamellar to Quadrangular to Hexagonal

Co-reporter:Xu Zhang;Ting Chen;Qing Chen;Guo-Jun Deng Dr.;Qing-Hua Fan Dr. Dr.

Chemistry - A European Journal 2009 Volume 15( Issue 38) pp:9669-9673

Publication Date(Web):

DOI:10.1002/chem.200901618

Structural Diversity of a Monodendron Molecule Self-Assembly in Different Solvents Investigated by Scanning Tunneling Microscopy: From Dispersant to Counterpart

Co-reporter:Xu Zhang, Qing Chen, Guo-Jun Deng, Qing-Hua Fan and Li-Jun Wan

The Journal of Physical Chemistry C 2009 Volume 113(Issue 36) pp:16193-16198

Publication Date(Web):August 18, 2009

DOI:10.1021/jp9058356

A monodendron molecule, 5-(benzyloxy)isophthalic acid derivative (BIC, C47H76O7), has been employed to fabricate self-assembly on graphite surface. The molecules were dissolved in different solvents of 1-phenyloctane, 1,2,4-trichlorobenzene (TCB), and 1-octanoic acid. The effects of these solvents on BIC self-assemblies were investigated by scanning tunneling microscopy (STM) at the liquid/graphite interface. It is found that 1-phenyloctane exerts as a dispersant without coadsorption in the self-assembly, although a structural transformation of BIC adlayer from lamella to hexamer can be seen with concentration decrease. TCB solvent coadsorbs with BIC molecules and affects the structure and stability of the BIC adlayer. In contrast, a stable BIC linear adlayer is formed with the coadsorption of 1-octanoic acid. The intermolecular hydrogen bonds between solvent molecule 1-octanoic acid and the BIC molecule are responsible for the formation of the linear structure. Furthermore, the effect of mixed solvents on BIC adlayer was also investigated. The results demonstrate that the solvent plays the important role of not only a simple dispersant but also a counterpart in forming the two-dimensional (2D) monodendron molecular self-assembly and provides an efficient approach to fabricating and controlling monodendron molecular nanostructure by changing solvent and molecular concentration.

Adsorption of TTF, TCNQ and TTF-TCNQ on Au(111): An in situ ECSTM study

Co-reporter:HuiJuan Yan;ShanShan Li;CunJi Yan;Qing Chen

Science China Chemistry 2009 Volume 52( Issue 5) pp:559-565

Publication Date(Web):2009/05/01

DOI:10.1007/s11426-009-0083-2

The adsorption and adlayer structures of tetrathiofulvalene (TTF), tetracyanoquinodimethane (TCNQ) and TTF-TCNQ on Au(111) have been systematically investigated by in situ electrochemical scanning tunneling microscopy (ECSTM) and cyclic voltammetry in 0.1 mol L−1 HClO4. All the three molecules were found to form well-ordered adlayers in the double-layer potential region of Au(111). For TTF and TCNQ adlayers, (6×3) and (4×7) structures have been observed, respectively. A structural transition was observed on TCNQ adlayer at potential negative of 0.08 V vs. the reversible hydrogen electrode (RHE), and induced a new phase with (3\( \sqrt 3 \) × 12) structure. On the other hand, the charge transfer complex, TTF-TCNQ, self-organized into ordered domains with a lamellar structure different from those of the pure TTF and TCNQ adlayers on Au(111). Its packing arrangement was comparable to surface structures of either single crystal or thin film of TTF-TCNQ.

Tin-Nanoparticles Encapsulated in Elastic Hollow Carbon Spheres for High-Performance Anode Material in Lithium-Ion Batteries

Co-reporter:Wei-Ming Zhang;Jin-Song Hu;Yu-Guo Guo;Shu-Fa Zheng;Liang-Shu Zhong;Wei-Guo Song

Advanced Materials 2008 Volume 20( Issue 6) pp:1160-1165

Publication Date(Web):

DOI:10.1002/adma.200701364

Nanostructured Materials for Electrochemical Energy Conversion and Storage Devices

Co-reporter:Yu-Guo Guo;Jin-Song Hu

Advanced Materials 2008 Volume 20( Issue 15) pp:2878-2887

Publication Date(Web):

DOI:10.1002/adma.200800627

Ion-Transfer-Based Growth: A Mechanism for CuTCNQ Nanowire Formation

Co-reporter:Heng-Xing Ji;Jin-Song Hu;Yu-Guo Guo;Wei-Guo Song

Advanced Materials 2008 Volume 20( Issue 24) pp:4879-4882

Publication Date(Web):

DOI:10.1002/adma.200702766

Introducing Dual Functional CNT Networks into CuO Nanomicrospheres toward Superior Electrode Materials for Lithium-Ion Batteries

Co-reporter:Shu-Fa Zheng, Jin-Song Hu, Liang-Shu Zhong, Wei-Guo Song, Li-Jun Wan and Yu-Guo Guo

Chemistry of Materials 2008 Volume 20(Issue 11) pp:3617

Publication Date(Web):May 14, 2008

DOI:10.1021/cm7033855

An optimized nanostructure design of electrode materials for high-performance lithium-ion batteries was realized by introducing three-dimensional (3D) carbon nanotube (CNT) networks into transition metal oxide nanomicrospheres. A CuO−CNT composite was selected as a typical example of the optimized design. Self-assembled CuO and CuO−CNT nanomicrospheres have been successfully synthesized by a simple solution method and investigated with SEM, TEM, XRD, and electrochemical experiments. The CuO−CNT composite spheres exhibit remarkably enhanced cycling performance and rate performance compared with CuO spheres when being used as anode materials in lithium-ion batteries. It benefits from an as-formed 3D network of CNTs, which has dual functions, viz. a 3D current collector network and an elastic buffer.

Controllable crystalline structure of fullerene nanorods and transport properties of an individual nanorod

Co-reporter:Heng-Xing Ji, Jin-Song Hu, Li-Jun Wan, Qing-Xin Tang and Wen-Ping Hu

Journal of Materials Chemistry A 2008 vol. 18(Issue 3) pp:328-332

Publication Date(Web):23 Nov 2007

DOI:10.1039/B712696D

Single-crystalline pristine C60nanorods with fcc crystal structure were synthesized by solvent-induced self-assembly followed by heat treatment. The length and length-to-width ratio of C60nanorods were tunable by controlling the concentration of C60 molecules in the stock solution. Devices consisting of individual fcc nanorods were fabricated by a focused ion beam (FIB) technique. For comparison, nanorods of hcp structure were synthesized and devices consisting of individual hcp nanorods were fabricated also. The transport properties of an individual C60nanorod suggested that the fcc nanorods exhibited higher conductivity than the hcp nanorods, i.e., the transport properties of C60nanorods exhibited a strong phase dependence. The temperature dependence of the devices indicated the thermally activated carrier injection of the fcc nanorods. The activation energies of the nanorods are much smaller than those of the bulk crystals of C60, indicating easier carrier injection of the fcc nanorods and their potential applications for the fabrication of efficient nanodevices. The good operational stability of individual C60nanorod based devices under sustained high dc voltage suggested their application as stable units in micro electronics or chemical sensor systems.

TNT adsorption on Au(111): electrochemistry and adlayer structure

Co-reporter:Rui Wen, Hong-Xia Zhang, Cun-Ji Yan, Hui-Juan Yan, Ge-Bo Pan and Li-Jun Wan

Chemical Communications 2008 (Issue 16) pp:1877-1879

Publication Date(Web):18 Mar 2008

DOI:10.1039/B719888D

Electrochemistry and adlayer structure of trinitrotoluene (TNT) on an Au(111) electrode were investigated using cyclic voltammetry and in situ electrochemical scanning tunneling microscopy (ECSTM).

ZnOEP based phototransistor: signal amplification and light-controlled switch

Co-reporter:Heng-Xing Ji, Jin-Song Hu and Li-Jun Wan

Chemical Communications 2008 (Issue 23) pp:2653-2655

Publication Date(Web):15 May 2008

DOI:10.1039/B805204B

A phototransistor with a field-effect transistor configuration was fabricated using a single zinc octaethylporphyrin (ZnOEP) nanorod; the device showed ability in signal amplification and reversible light-controlled switching.

Facile synthesis of nanoporous anatase spheres and their environmental applications

Co-reporter:Liang-Shu Zhong, Jin-Song Hu, Li-Jun Wan and Wei-Guo Song

Chemical Communications 2008 (Issue 10) pp:1184-1186

Publication Date(Web):11 Jan 2008

DOI:10.1039/B718300C

Highly nanoporous TiO2 (anatase) spheres with an excellent ability in environmental applications have been successfully prepared viain situhydrolysis of titanium glycolate precursor spheres.

Structural transition of molecular assembly under photo-irradiation: an STM study

Co-reporter:Dong Wang, Qing Chen and Li-Jun Wan

Physical Chemistry Chemical Physics 2008 vol. 10(Issue 43) pp:6467-6478

Publication Date(Web):30 Sep 2008

DOI:10.1039/B810304F

Surface photochemistry processes have attracted increasing interest from both fundamental and application viewpoints. The development of scanning tunneling microscopy (STM) provides us a great opportunity to investigate photo-induced structural transition on surface with a high spatial resolution in real space. The detailed structural information of the organization of photoresponsive molecules in the adlayer is resolved and their structural transition during the photochemical processes is observed. The photo-induced structural and property transitions inspire new application potential of photoresponsive molecules in the field of molecular devices, supramolecular assembly and advanced materials.

STM investigation of the dependence of alkane and alkane (C18H38, C19H40) derivatives self-assembly on molecular chemical structure on HOPG surface

Co-reporter:Qing Chen, Hui-Juan Yan, Cun-Ji Yan, Ge-Bo Pan, Li-Jun Wan, Guo-Yong Wen, De-Qing Zhang

Surface Science 2008 Volume 602(Issue 6) pp:1256-1266

Publication Date(Web):15 March 2008

DOI:10.1016/j.susc.2008.01.030

Alkane molecules and their derivatives are composed of alkyl chain and functional groups that dominate the interactions of intermolecule and molecule/substrate and result in different self-assemblies on solid surface. In the present paper, the self-assemblies of alkanes and alkane (C18H38, C19H40) derivatives are studied on HOPG surface at room temperature in ambient conditions by scanning tunneling microscopy (STM) to understand the structure and stability of these self-assemblies and to reveal the dependence of their self-assemblies on their chemical structures. It is found that the alkane molecules with short alkyl chains such as tridecane (C13H28), tetradecane (C14H30) and pentadecane (C15H32) can form lamellar structures on HOPG and be steadily imaged by STM. On the other hand, linear or herringbone structures can be observed in the self-assemblies formed by a series of derivatives of C18H38 and C19H40. The results are discussed based on STM results to understand the structures and structural stability of alkane molecular self-assemblies.

Structural selection of graphene supramolecular assembly oriented by molecular conformation and alkyl chain

Co-reporter:Zhong-Tao Li;Zhao-Hui Wang;Qing Chen;Hui-Juan Yan;Wei-Guo Song;Ting Chen;Ge-Bo Pan;Bo Shang;Lan-Feng Yuan;Jin-Long Yang

PNAS 2008 Volume 105 (Issue 44 ) pp:16849-16854

Publication Date(Web):2008-11-04

DOI:10.1073/pnas.0809427105

Graphene molecules, hexafluorotribenzo[a,g,m]coronene with n-carbon alkyl chains (FTBC-Cn, n = 4, 6, 8, 12) and Janus-type “double-concave” conformation, are used to fabricate self-assembly on highly oriented pyrolytic graphite surface. The structural dependence of the self-assemblies with molecular conformation and alkyl chain is investigated by scanning tunneling microscopy and density functional theory calculation. An interesting reverse face “up–down” way is observed in FTBC-C4 assembly due to the existence of hydrogen bonds. With the increase of the alkyl chain length and consequently stronger van der Waals interaction, the molecules no longer take alternating “up–down” orientation in their self-assembly and organize into various adlayers with lamellar, hexagonal honeycomb, and pseudohoneycomb structures based on the balance between intermolecular and molecule-substrate interactions. The results demonstrate that the featured “double-concave” molecules are available block for designing graphene nanopattern. From the results of scanning tunneling spectroscopy measurement, it is found that the electronic property of the featured graphene molecules is preserved when they are adsorbed on solid surface.

La(OH)3 Hollow Nanostructures with Trapezohedron Morphologies Using a New Kirkendall Diffusion Couple

Co-reporter:Fang Niu, An-Min Cao, Wei-Guo Song and Li-Jun Wan

The Journal of Physical Chemistry C 2008 Volume 112(Issue 46) pp:17988-17993

Publication Date(Web):2017-2-22

DOI:10.1021/jp807779j

A highly symmetric trapezohedron of lanthanum glycolate precursor is converted to hollow La(OH)3 with the same morphology via a simple hydrothermal treatment of the lanthanum glycolate precursor in an alkaline solution. The formation process of the hollow structure is the result of the Kirkendall effect, in which a new diffusion couple, water and lanthanum glycolate, is proposed. This expands the scope of the Kirkendall effect in material fabrication. The hollow La(OH)3 trapezohedron can be further converted into hollow La2O3 material by calcinations. The as-prepared La(OH)3 hollow trapezohedron shows excellent ability to remove certain organic pollutants in wastewater.

Effect of the Bridge Alkylene Chain on Adlayer Structure and Property of Functional Oligothiophenes Studied with Scanning Tunneling Microscopy and Spectroscopy

Co-reporter:Zhi-Yong Yang, Hui-Min Zhang, Ge-Bo Pan and Li-Jun Wan

ACS Nano 2008 Volume 2(Issue 4) pp:743

Publication Date(Web):March 26, 2008

DOI:10.1021/nn7004443

Five dual-quinquethiophene self-assemblies are prepared on a highly oriented pyrolytic graphite (HOPG) surface. The dual-quinquethiophenes are quinquethiophenes (5T)-di to hexamethylene (n, 2–6)-quinquethiophenes (5T), abbreviated as 5T-n-5T (n = 2–6). The effect of the bridge alkylene chains on the structure and property of the five assemblies are investigated by scanning tunneling microscopy (STM). It is found that all 5T-n-5T molecules form ordered adlayers on a HOPG surface with stripe feature. The alkylene bridge part in a molecule appears in a dark contrast in an STM image. Intriguingly, the thiophene backbones of individual molecules in the adlayer always keep an angle with the direction of molecular stripes. With alkylene bridge length increasing, different structures are found in 5T-5-5T and 5T-6-5T assemblies. To understand the effect of bridge chains on single molecular property, scanning tunneling spectroscopy is used to probe the electronic property of the different adlayers. The results will be important in surface engineering by self-assembly and molecular device fabrication with oligothiophenes.Keywords: oligothiophene; self-assembly; STM; STS;

Facile solution synthesis of hexagonal Alq3 nanorods and their field emission properties

Co-reporter:Jin-Song Hu, Heng-Xing Ji, An-Min Cao, Zheng-Xi Huang, Yang Zhang, Li-Jun Wan, An-Dong Xia, Da-Peng Yu, Xiang-Min Meng and Shuit-Tong Lee

Chemical Communications 2007 (Issue 29) pp:3083-3085

Publication Date(Web):17 May 2007

DOI:10.1039/B704106C

A facile self-assembly growth route assisted by surfactant has been developed to synthesize tris(8-hydroxyquinoline)aluminium (Alq3) nanorods with regular hexagonal shape and good crystallinity, which exhibit field-emission characteristics with a very low turn-on field of ca. 3.1 V µm−1 and a high field-enhancement factor of ca. 1300.

Scanning tunneling microscopy of the formation, transformation, and property of oligothiophene self-organizations on graphite and gold surfaces

Co-reporter:Zhi-Yong Yang;Hui-Min Zhang;Cun-Ji Yan;Shan-Shan Li;Hui-Juan Yan;Wei-Guo Song;

Proceedings of the National Academy of Sciences 2007 104(10) pp:3707-3712

Publication Date(Web):February 28, 2007

DOI:10.1073/pnas.0611585104

Two alkyl-substituted dual oligothiophenes, quarterthiophene (4T)-trimethylene (tm)-octithiophene (8T) and 4T-tm-4T, were used to fabricate molecular structures on highly oriented pyrolytic graphite and Au(111) surfaces. The resulted structures were investigated by scanning tunneling microscopy. The 4T-tm-8T and 4T-tm-4T molecules self-organize into long-range ordered structures with linear and/or quasi-hexagonal patterns on highly oriented pyrolytic graphite at ambient temperature. Thermal annealing induced a phase transformation from quasi-hexagonal to linear in 4T-tm-8T adlayer. The molecules adsorbed on Au(111) surface in randomly folded and linear conformation. Based on scanning tunneling microscopy results, the structural models for different self-organizations were proposed. Scanning tunneling spectroscopy measurement showed the electronic property of individual molecules in the patterns. These results are significant in understanding the chemistry of molecular structure, including its formation, transformation, and electronic properties. They also help to fabricate oligothiophene assemblies with desired structures for future molecular devices.

2D self-assembly of 1,3,2-dioxaborine derivatives on HOPG

Co-reporter:JiQun Lu;CunJi Yan;HuiJuan Yan;LiJun Wan

Science Bulletin 2007 Volume 52( Issue 18) pp:2486-2490

Publication Date(Web):2007 September

DOI:10.1007/s11434-007-0341-7

Two-dimensional (2D) self-assembly of two 1,3,2-dioxaborine derivatives was investigated by STM. The molecules consist of π system and steric end groups. A droplet of toluene solution containing the molecules was deposited onto HOPG for preparing the assemblies. STM images showed that the molecular structures affect the assembly structure. The dipole-dipole interaction and steric repulsion played important roles in the formation of the self-assembled monolayers.

Bis(ethylenedithio)tetrathiafulvalene Charge-Transfer Salt Nanotube Arrays

Co-reporter:H.-X. Ji;W.-P. Hu;J.-S. Hu;L.-J. Wan;Q.-X. Tang;W.-G. Song

Advanced Materials 2006 Volume 18(Issue 20) pp:2753-2757

Publication Date(Web):20 SEP 2006

DOI:10.1002/adma.200600398

β″-(BEDT-TTF)₄[H₂O·Fe(C₂O₄)₃]· C₆H₅NO₂nanotube arrays with uniform size and a highly ordered arrangement are fabricated via an electrocrystallization process on porous anodic aluminum oxide template. The current–voltage characteristics of nanotube arrays and single nanotubes as well as the temperature dependence of the resistance of the nanotube arrays are reported. This method is an important step toward the development of nanoscale electronic devices and chemical sensors based on these organic materials.

Self-Assembled 3D Flowerlike Iron Oxide Nanostructures and Their Application in Water Treatment

Co-reporter:W.-G. Song;L.-S. Zhong;H.-P. Liang;J.-S. Hu;A.-M. Cao;L.-J. Wan

Advanced Materials 2006 Volume 18(Issue 18) pp:2426-2431

Publication Date(Web):12 SEP 2006

DOI:10.1002/adma.200600504

An ethylene-glycol-mediated self-assembly process is adopted to synthesize 3D flowerlike nanostructures of iron oxide (see figure) using inexpensive and nontoxic ferric chloride. A two-stage growth process is identified during the morphological evolution of the iron oxide precursor. α-Fe₂O₃, γ-Fe₂O₃, and Fe₃O₄ with the same flowerlike structure are readily obtained from the same precursor but by different calcination procedures. The as-obtained iron oxides show excellent ability to remove various pollutants from water.

Ordered Self-assembled Monolayers of β-dicarbonyl Derivatives Studied by STM

Co-reporter:Yuxia Diao, Dirk Rohde, Lijun Wan

Acta Physico-Chimica Sinica 2006 Volume 22(Issue 6) pp:691-695

Publication Date(Web):June 2006

DOI:10.1016/S1872-1508(06)60028-4

AbstractThe adsorption of four β-dicarbonyl derivatives on highly oriented pyrolytic graphite (HOPG) surface was studied by scanning tunneling microscopy (STM) in an ambient environment. All the molecules include a π-conjugated part and alkyl chains in their chemical structures. The molecules were dissolved in toluene solvent and a drop of the solution was deposited on HOPG to form self-assembled adlayers. The characteristic stripe-like structure in the self-assembled monolayers (SAMs) on the high-resolution STM images of the compounds was observed. Different molecular structures led to different SAMs. It was found that noncovalent interactions such as hydrogen bonds and dipole-dipole interactions played an important role in the formation of different SAMs.

From a Lamellar to Hexagonal Self-Assembly of Bis(4,4′-(m,m′-di(dodecyloxy)phenyl)-2,2′-difluoro-1,3,2-dioxaborin) Molecules: A trans-to-cis-Isomerization-Induced Structural Transition Studied with STM

Co-reporter:Dirk Rohde Dr.;Cun-Ji Yan;Hui-Juan Yan Dr. Dr.

Angewandte Chemie 2006 Volume 118(Issue 24) pp:

Publication Date(Web):4 MAY 2006

DOI:10.1002/ange.200600725

Erst aufwärmen! Einfaches Tempern löst die trans-cis-Isomerisierung von Molekülen einer Adsorbatschicht aus und wandelt deren Gesamtsymmetrie von lamellar in hexagonal um. Je nach Temperatur können reine Adsorbatschichten aus trans- oder cis-Isomeren erhalten werden.

Insights into the Mechanism of Methanol-to-Olefin Conversion at Zeolites with Systematically Selected Framework Structures

Co-reporter:Zhi-Min Cui;Qiang Liu;Wei-Guo Song

Angewandte Chemie 2006 Volume 118(Issue 39) pp:

Publication Date(Web):13 SEP 2006

DOI:10.1002/ange.200602488

Genauer Blick: Der so genannte Kohlenwasserstoffpool-Mechanismus funktioniert bei der Umwandlung von Methanol in Olefine (MTO-Prozess) am Zeolith ZSM-22 wegen der engen Gerüstkanäle (0.57 nm) nicht. Dafür bot dieses System die Möglichkeit zu genauen mechanistischen Studien ohne Störung durch Sekundärreaktionen. Die dabei erhaltenen H/D-Austauschmuster von Toluol sprechen für einen Schälmechanismus (paring mechanism).

From a Lamellar to Hexagonal Self-Assembly of Bis(4,4′-(m,m′-di(dodecyloxy)phenyl)-2,2′-difluoro-1,3,2-dioxaborin) Molecules: A trans-to-cis-Isomerization-Induced Structural Transition Studied with STM

Co-reporter:Dirk Rohde Dr.;Cun-Ji Yan;Hui-Juan Yan Dr. Dr.

Angewandte Chemie International Edition 2006 Volume 45(Issue 24) pp:

Publication Date(Web):4 MAY 2006

DOI:10.1002/anie.200600725

Lick into shape: Molecular adlayer symmetry can be transformed from lamellar to hexagonal through a thermal-annealing process which causes a trans-to-cis isomerization of the molecules within the adlayer. Different temperatures resulted in the formation of pure trans- and cis-isomer adlayers on the surface.

Insights into the Mechanism of Methanol-to-Olefin Conversion at Zeolites with Systematically Selected Framework Structures

Co-reporter:Zhi-Min Cui;Qiang Liu;Wei-Guo Song

Angewandte Chemie International Edition 2006 Volume 45(Issue 39) pp:

Publication Date(Web):13 SEP 2006

DOI:10.1002/anie.200602488

Com-paring mechanisms: The so-called hydrocarbon pool mechanism does not operate with zeolite ZSM-22 in the methanol-to-olefin (MTO) conversion process as a result of the narrow channels (0.57 nm) in its framework structure. However, this provided a condition free of secondary reactions for detailed mechanistic studies, with H/D exchange patterns of toluene suggesting a paring mechanism.

Structural Comparison of Self-Organized Adlayers of Ligands and Their Metal-Coordinated Complexes on a Au(111) Surface: An STM Study

Co-reporter:Qun-Hui Yuan Dr.

Chemistry - A European Journal 2006 Volume 12(Issue 10) pp:

Publication Date(Web):19 JAN 2006

DOI:10.1002/chem.200500844

Scanning tunneling microscopy (STM) was employed to investigate the adsorption of the linear-spacer-bridged ligands bis(pyrrol-2-yl-methyleneamine) (BPMB and BPMmB), and their Zn^II-coordinated complexes, BPMB/Zn^II and BPMmB/Zn^II, onto a Au(111) surface in 0.1 M HClO₄ solution. Both the ligands, with different spacer bridges, and their Zn^II complexes adsorb onto the Au(111) surface and self-organize into highly ordered two-dimensional arrays. The complexes BPMB/Zn^II and BPMmB/Zn^II appear in helical and triangular conformations, respectively, consistent with their chemical structures. Although the metal complexes include ligands, the assembled structures and adlayer symmetries of the ligands and complexes are totally different. The structures and intramolecular features obtained by high-resolution STM imaging are discussed. The results should be important in fabricating surface supramolecular structures.

Template Synthesis of Sc@C82(I) Nanowires and Nanotubes at Room Temperature

Co-reporter:C.-J. Li;Y.-G. Guo;B.-S. Li;C.-R. Wang;L.-J. Wan;C.-L. Bai

Advanced Materials 2005 Volume 17(Issue 1) pp:

Publication Date(Web):13 JAN 2005

DOI:10.1002/adma.200400155

Metallofullerene-based nanowire and nanotube arrays are fabricated for the first time using a technique that allows the diameter, length, and morphology of the non-crystalline Sc@C₈₂ nanostructures to be controlled by adjusting the experimental conditions. The Figure shows the geometrical structure of Sc@C₈₂.

Tin/Platinum Bimetallic Nanotube Array and its Electrocatalytic Activity for Methanol Oxidation

Co-reporter:Y.-G. Guo;J.-S. Hu;H.-M. Zhang;H.-P. Liang;L.-J. Wan;C.-L. Bai

Advanced Materials 2005 Volume 17(Issue 6) pp:

Publication Date(Web):24 JAN 2005

DOI:10.1002/adma.200400486

A well-aligned Sn/Pt bimetallic nanotube array is fabricated by directly evaporating tin onto a porous anodic aluminum oxide film followed by electrodeposition of platinum. The composite nanostructures contain a large number of Pt nanoparticles inlaying the inner-wall surfaces of the Sn nanotubes. The novel Sn/Pt nanotube array shows remarkable activity toward methanol oxidation and hence could be used as an effective anode for direct methanol fuel cells (see Figure).

TiO2-Based Composite Nanotube Arrays Prepared via Layer-by-Layer Assembly

Co-reporter:Y.-G. Guo;J.-S. Hu;H.-P. Liang;L.-J. Wan;C.-L. Bai

Advanced Functional Materials 2005 Volume 15(Issue 2) pp:

Publication Date(Web):14 FEB 2005

DOI:10.1002/adfm.200305098

A simple and versatile technique has been developed to prepare TiO₂ and TiO₂-based composite (TiO₂–CdS and TiO₂–Au) nanotube arrays. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV-vis spectroscopy, and photoluminescence (PL) spectroscopy are used to characterize their morphology, structure, composition, and properties. The TiO₂–CdS nanotubes contained many TiO₂ and CdS quantum dots and exhibited a novel PL band in the blue-wavelength range. The reported strategy will be useful for fabricating nanoparticle–nanoparticle composite nanostructure arrays, which are suitable for applications in catalysis, chemical sensors, nanoelectrodes, and nanodevices.

Monitoring molecular motion and structure near defect with STM

Co-reporter:Jian-Ru Gong, Sheng-Bin Lei, Ge-Bo Pan, Li-Jun Wan, Qing-Hua Fan, Chun-Li Bai

Colloids and Surfaces A: Physicochemical and Engineering Aspects 2005 Volumes 257–258() pp:9-13

Publication Date(Web):5 May 2005

DOI:10.1016/j.colsurfa.2004.10.088

The diffusion dynamics and enantiomeric structure of the alkyl-substituted isophthalic acid adlayer physisorbed on highly oriented pyrolytic graphite (HOPG) have been investigated in the vicinity of defect by scanning tunneling microscopy (STM). Through molecular motion and reorientation, the defect in the monolayer is filled and an ordered two-dimensional (2D) packing appears. Moreover, an enantiomeric structure is also observed. These findings can be explained by the role of molecular mobility and the cooperation of molecule/molecule and molecule/substrate interactions. The result provides experimental evidences for molecular diffusion and chirality in two dimensions.

Nanoarchitectured metal film electrodes with high electroactive surface areas

Co-reporter:Yu-Guo Guo, Hui-Min Zhang, Jin-Song Hu, Li-Jun Wan, Chun-Li Bai

Thin Solid Films 2005 Volume 484(1–2) pp:341-345

Publication Date(Web):22 July 2005

DOI:10.1016/j.tsf.2005.01.092

Well-defined nanoarchitectured metal film electrodes (NMFEs) with high electroactive surface areas relative to corresponding metal macroelectrode have been fabricated by direct evaporating metal onto porous anodic aluminum oxide films in a two-step route. The so-prepared metal electrodes have high dense hollow nanostructure arrays upstanding on their surfaces and thin thickness within several hundred nanometers, which endow them with enhanced electroactive surface areas relative to disk-shaped electrodes of macroscopic dimensions and the feature of reduction of cost. Because of the rich nano-surface, these NMFEs will find use in a number of applications that involve sensing, analysis, and catalysis.

Mass Production and High Photocatalytic Activity of ZnS Nanoporous Nanoparticles

Co-reporter:Jin-Song Hu;Ling-Ling Ren;Yu-Guo Guo;Han-Pu Liang;An-Min Cao Dr.;Chun-Li Bai Dr.

Angewandte Chemie 2005 Volume 117(Issue 8) pp:

Publication Date(Web):14 JAN 2005

DOI:10.1002/ange.200462057

Die Selbstorganisation hexagonaler 3 bis 5 nm großer ZnS-Nanokristalle kann zur Herstellung großer Mengen an nanoporösen Zinksulfid-Nanopartikeln (ZnS-NPNPs) genutzt werden. Die einheitlichen, sphärischen NPNPs sind monodispers und haben spezifische Oberflächen von 156 m² g⁻¹. Sie katalysieren bei Raumtemperatur den Photoabbau von Eosin B wirkungsvoller als das Titandioxid Degussa P25 oder ZnS-Nanokristalle (siehe Bild).

The Effect of Polarity on Coadsorbed Molecular Nanostructures of Substituted Phthalocyanine and Thiol Molecules

Co-reporter:Zhi-Yong Yang;Sheng-Bin Lei Dr.;Li-Huan Gan ;Chen Wang ;Chun-Li Bai

ChemPhysChem 2005 Volume 6(Issue 1) pp:

Publication Date(Web):13 DEC 2004

DOI:10.1002/cphc.200400293

Different adlayer structures were fabricated by coadsorption of differently substituted phthalocyanine/thiol molecules and investigated using scanning tunnelling microscopy (STM, see graphic). The molecular polarity was considered to be responsible for the formation of different adlayer structures.

Self-Assembled Vanadium Pentoxide (V2O5) Hollow Microspheres from Nanorods and Their Application in Lithium-Ion Batteries

Co-reporter:An-Min Cao;Jin-Song Hu;Han-Pu Liang Dr.

Angewandte Chemie 2005 Volume 117(Issue 28) pp:

Publication Date(Web):8 JUN 2005

DOI:10.1002/ange.200500946

Igel- oder nestartige Mikrokugeln aus V₂O₅ entstehen in einem Polyol-vermittelten Prozess durch Aggregation von V₂O₅-Nanostäbchen. Bei niedrigen Konzentrationen des Ausgangsmaterials [V(acac)₃] wird die Nestform bevorzugt, bei höheren Konzentrationen entstehen igelförmige Gebilde (siehe Bild). Die V₂O₅-Mikrokugeln zeigen bemerkenswerte elektrochemische Eigenschaften als Kathodenmaterial in Lithiumionen-Batterien.

Self-Assembled Vanadium Pentoxide (V2O5) Hollow Microspheres from Nanorods and Their Application in Lithium-Ion Batteries

Co-reporter:An-Min Cao;Jin-Song Hu;Han-Pu Liang Dr.

Angewandte Chemie International Edition 2005 Volume 44(Issue 28) pp:

Publication Date(Web):8 JUN 2005

DOI:10.1002/anie.200500946

“Hedgehog” or “nest” microspheres of V₂O₅ are formed when nanorods of V₂O₅ are synthesized in a mediated polyol process. When the concentration of the starting material is low, a nest shape is preferred, whereas a high concentration of [V(acac)₃] affords hedgehog-shaped microspheres (see picture). The V₂O₅ microspheres exhibit remarkable electrochemical properties when used as the cathode material in a lithium-ion battery.

Mass Production and High Photocatalytic Activity of ZnS Nanoporous Nanoparticles

Co-reporter:Jin-Song Hu;Ling-Ling Ren;Yu-Guo Guo;Han-Pu Liang;An-Min Cao Dr.;Chun-Li Bai Dr.

Angewandte Chemie International Edition 2005 Volume 44(Issue 8) pp:

Publication Date(Web):14 JAN 2005

DOI:10.1002/anie.200462057

Self-assembly of hexagonal 3–5-nm ZnS nanocrystals can be used for the large-scale production of zinc sulfide nanoporous nanoparticles (NPNPs). The uniform, spherical NPNPs are monodisperse and have surface areas on the order of 156 m² g⁻¹. The ZnS NPNPs are more effective photocatalysts than Degussa P25 titania or ZnS nanocrystals in the photodegradation of eosin B at ambient temperature (see picture).

Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

Co-reporter:Peter J. Stang;Jian-Ru Gong;Chun-Li Bai;Hershel Jude;Qun-Hui Yuan

PNAS 2005 Volume 102 (Issue 4 ) pp:971-974

Publication Date(Web):2005-01-25

DOI:10.1073/pnas.0409145102

A self-assembled supramolecular metallacyclic rectangle was investigated with scanning tunneling microscopy on highly oriented pyrolytic graphite and Au(111) surfaces. The rectangles spontaneously adsorb on both surfaces and self-organize into well ordered adlayers. On highly oriented pyrolytic graphite, the long edge of the rectangle stands on the surface, forming a 2D molecular network. In contrast, the face of the rectangle lays flat on the Au(111) surface, forming linear chains. The structures and intramolecular features obtained through high-resolution scanning tunneling microscopy imaging are discussed.

The effects of annealing on the structures and electrical conductivities of fullerene-derived nanowires

Co-reporter:Yu-Guo Guo, Li-Jun Wan, Cong-Ju Li, Dong-Min Chen, Chen Wang, Chun-Ru Wang, Chun-Li Bai and Yan-Guo Wang

Journal of Materials Chemistry A 2004 vol. 14(Issue 5) pp:914-918

Publication Date(Web):20 Jan 2004

DOI:10.1039/B311449J

We have succeeded in fusing C60 clusters into one-dimensional nanowires by electrophoretic deposition using porous anodic aluminium oxide (AAO) membranes as templates. The C60 clusters are introduced through a dc electric field and polymerized in the channels. Here we present the results on the effects of annealing on the structures and electrical conductivities of the fullerene-derived nanowires. By changing the annealing temperature we found that the grain sizes became large at 523 K and 673 K while damaged to amorphous carbon resulted at 823 K, as determined by Fourier transform infrared (FTIR) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The measurements of their electrical conductivities show their semiconducting behavior with resistance varied by more than two orders of magnitude after annealing.

Controllable AuPt bimetallic hollow nanostructures

Co-reporter:Han-Pu Liang, Yu-Guo Guo, Hui-Min Zhang, Jin-Song Hu, Li-Jun Wan and Chun-Li Bai

Chemical Communications 2004 (Issue 13) pp:1496-1497

Publication Date(Web):24 May 2004

DOI:10.1039/B402745K

We describe a facile procedure for one step, large-scale synthesis of AuPt bimetallic hollow tube-like 1-D nanomaterials and hollow nanospheres, which can be easily manipulated by merely changing the concentration of citric acid.

Adlayer structures of dl-homocysteine and l-homocysteine thiolactone on Au(1 1 1) surface: an in situ STM study

Co-reporter:Hui-Min Zhang, Gui-Jin Su, Dong Wang, Li-Jun Wan, Gang Jin, Chun-Li Bai, Xianliang Zhou

Electrochimica Acta 2004 Volume 49(9–10) pp:1629-1633

Publication Date(Web):15 April 2004

DOI:10.1016/j.electacta.2003.12.002

The adsorption of dl-homocysteine (Hcy) and l-homocysteine thiolactone (HTL) on Au(1 1 1) electrode was investigated in 0.1 M HClO4 by cyclic voltammetry and in situ scanning tunneling microscopy (STM). Hcy and HTL molecules formed highly ordered adlayers on Au(1 1 1) surface. High-resolution STM images revealed the orientation and packing arrangement in the ordered adlayers. Hcy molecules formed ()R30° adlayer structure and H-bonds between carboxyl groups were assumed to be responsible for the origin of tail-to-tail or head-to-head molecular arrangement, while HTL molecules formed (4×6) adlayer structure, and two different orientations and appearances in the ordered adlayer were found. Structural models were proposed for the two adlayers.

Dimerization of three xanthene dyes on Au(1 1 1) surface

Co-reporter:Gui-Jin Su, Shu-Xia Yin, Li-Jun Wan, Jin-Cai Zhao, Chun-Li Bai

Surface Science 2004 Volume 551(Issue 3) pp:204-212

Publication Date(Web):1 March 2004

DOI:10.1016/j.susc.2003.12.046

The adsorption structures of three xanthene dyes (rhodamine B (Rh B), fluorescein and eosin) on Au(1 1 1) in HClO4 solution, have been investigated by in situ scanning tunneling microscopy (STM) and cyclic voltammetry. High-resolution STM images reveal the molecular orientation and packing arrangement in the ordered adlayers. A (5 × 10) structure is found on Rh B adlayer. (5 × 8) structures are observed on fluorescein and eosin adlayers, respectively. An intriguing aspect of this work is that three xanthene molecules form dimeric structures on Au(1 1 1) surface. The electrostatic interaction and van der Waals force are responsible to the dimeric formation of Rh B, while the interaction between Br atoms and hydrogen bond correspond to the dimerization of eosin and fluorescein, respectively. The structural models are tentatively proposed for the three ordered adlayers. The results obtained will be helpful to understand the interaction mechanism of dimerization and the degradation mechanism of dye pollutant.

Pt Hollow Nanospheres: Facile Synthesis and Enhanced Electrocatalysts

Co-reporter:Han-Pu Liang;Hui-Min Zhang;Jin-Song Hu;Yu-Guo Guo;Chun-Li Bai

Angewandte Chemie 2004 Volume 116(Issue 12) pp:

Publication Date(Web):9 MAR 2004

DOI:10.1002/ange.200352956

Kugelrund und doch aktiv: Zur Präparation hohler Pt-Nanokügelchen (siehe TEM-Bild) mit verstärkter katalytischer Aktivität werden Co-Nanopartikel als „Opfertemplate“ verwendet. Die Methode wurde zur Fertigung von möglicherweise industriell anwendbaren Au-, Pd- und anderen Mono- und Multimetallnanokügelchen eingesetzt.

Pt Hollow Nanospheres: Facile Synthesis and Enhanced Electrocatalysts

Co-reporter:Han-Pu Liang;Hui-Min Zhang;Jin-Song Hu;Yu-Guo Guo;Chun-Li Bai

Angewandte Chemie International Edition 2004 Volume 43(Issue 12) pp:

Publication Date(Web):9 MAR 2004

DOI:10.1002/anie.200352956

A facile large-scale preparation of Pt hollow nanospheres (see TEM image) makes use of Co nanoparticle as sacrificial templates. The nanospheres exhibit enhanced electrocatalytic activity. This method has been extended to the fabrication of industrially potentially useful Au, Pd, and other mono- and multimetallic hollow nanospheres.

Novel electrocatalytic activity in layered Ni–Cu nanowire arrays

Co-reporter:Hui-Min Zhang, Yu-Guo Guo, Li-Jun Wan and Chun-Li Bai

Chemical Communications 2003 (Issue 24) pp:3022-3023

Publication Date(Web):07 Nov 2003

DOI:10.1039/B309624F

By using template synthesis method, well-defined composite Ni–Cu nanowire electrode arrays (CNNEAs) were prepared. Homogeneous nanoparticles of Ni in CNNEAs show extraordinary high catalytic activity, which was discussed in terms of the size effect of Ni nanoparticles.

Tuning molecular orientation with STM at the solid/liquid interface

Co-reporter:Qing-Min Xu, Mei-Juan Han, Li-Jun Wan, Chen Wang, Chun-Li Bai, Bing Dai and Jin-Long Yang

Chemical Communications 2003 (Issue 23) pp:2874-2875

Publication Date(Web):17 Oct 2003

DOI:10.1039/B308155A

Triptycene molecular orientation has been tuned with a STM tip at a Cu(111) surface in solution from flat, to tilt, to vertical. The tuning is completely bias dependent and reversible. The study is important in the fields of nanoscience and technology.

Configurations of a Calix[8]arene and a C60/Calix[8]arene Complex on a Au(111) Surface

Co-reporter:Ge-Bo Pan;Jun-Min Liu;Hui-Min Zhang Dr. Dr.;Qi-Yu Zheng Dr.;Chun-Li Bai Dr.

Angewandte Chemie International Edition 2003 Volume 42(Issue 24) pp:

Publication Date(Web):17 JUN 2003

DOI:10.1002/anie.200350432

Having a ball: Molecules of a calix[8]arene derivative, and the inclusion complex it forms with C₆₀ (see schematic)_, can be adsorbed onto a Au(111) surface in solution to yield self-organized highly ordered arrays. The structures of the two arrays have been investigated by scanning tunnelling microscopy, which gives clear evidence of the inclusion of the fullerene molecules. The stable configuration and well-defined arrays should be useful for the construction of nanostructures.

Configurations of a Calix[8]arene and a C60/Calix[8]arene Complex on a Au(111) Surface

Co-reporter:Ge-Bo Pan;Jun-Min Liu;Hui-Min Zhang Dr. Dr.;Qi-Yu Zheng Dr.;Chun-Li Bai Dr.

Angewandte Chemie 2003 Volume 115(Issue 24) pp:

Publication Date(Web):17 JUN 2003

DOI:10.1002/ange.200350432

Gut eingepasst: Die Moleküle eines Calix[8]arenderivates und seines C₆₀-Einschlusskomplexes (siehe Bild) werden auf Au(111)-Oberflächen unter Bildung hochgeordneter Domänen adsorbiert. Rastertunnelmikroskopische Untersuchungen an zwei Proben bestätigen den Einschluss der Fullerenmoleküle. Die Stabilität und der hohe Ordnungsgrad der Adsorbatstrukturen sind von Interesse für die Konstruktion von Nanostrukturen.

Structural transition of molecular assembly under photo-irradiation: an STM study

Co-reporter:Dong Wang, Qing Chen and Li-Jun Wan

Physical Chemistry Chemical Physics 2008 - vol. 10(Issue 43) pp:NaN6478-6478

Publication Date(Web):2008/09/30

DOI:10.1039/B810304F

Surface photochemistry processes have attracted increasing interest from both fundamental and application viewpoints. The development of scanning tunneling microscopy (STM) provides us a great opportunity to investigate photo-induced structural transition on surface with a high spatial resolution in real space. The detailed structural information of the organization of photoresponsive molecules in the adlayer is resolved and their structural transition during the photochemical processes is observed. The photo-induced structural and property transitions inspire new application potential of photoresponsive molecules in the field of molecular devices, supramolecular assembly and advanced materials.

Self-assembly and aggregation of melamine and melamine–uric/cyanuric acid investigated by STM and AFM on solid surfaces

Co-reporter:Xu Zhang, Ting Chen, Qing Chen, Ling Wang and Li-Jun Wan

Physical Chemistry Chemical Physics 2009 - vol. 11(Issue 35) pp:NaN7712-7712

Publication Date(Web):2009/06/24

DOI:10.1039/B907557G

The self-assembly and aggregation of melamine (M), and a mixture of melamine with uric/cyanuric acid (UA/CA) are investigated by performing scanning tunneling microscopy (STM) and atomic force microscopy (AFM) on graphite and mica surfaces at room temperature. Two-dimensional (2D) porous molecular networks and disordered adlayers are found, respectively, in the M and UA–M assembly on graphite. Uniformly dispersed nanoparticles of M and UA–M are found at various concentrations by AFM. Owing to complementary NH⋯O and NH⋯N hydrogen bonds, the CA–M mixture forms 2D densely packed adlayers and nanoscale crystals on graphite and aggregates into three-dimensional (3D) clusters on the surfaces. The size of the cluster is dependent on the molecular concentration. The results provide important information for the self-assembly of triazine compounds and are significant in the study of kidney disease related to melamine.

Controllable crystalline structure of fullerene nanorods and transport properties of an individual nanorod

Co-reporter:Heng-Xing Ji, Jin-Song Hu, Li-Jun Wan, Qing-Xin Tang and Wen-Ping Hu

Journal of Materials Chemistry A 2008 - vol. 18(Issue 3) pp:NaN332-332

Publication Date(Web):2007/11/23

DOI:10.1039/B712696D

Single-crystalline pristine C60nanorods with fcc crystal structure were synthesized by solvent-induced self-assembly followed by heat treatment. The length and length-to-width ratio of C60nanorods were tunable by controlling the concentration of C60 molecules in the stock solution. Devices consisting of individual fcc nanorods were fabricated by a focused ion beam (FIB) technique. For comparison, nanorods of hcp structure were synthesized and devices consisting of individual hcp nanorods were fabricated also. The transport properties of an individual C60nanorod suggested that the fcc nanorods exhibited higher conductivity than the hcp nanorods, i.e., the transport properties of C60nanorods exhibited a strong phase dependence. The temperature dependence of the devices indicated the thermally activated carrier injection of the fcc nanorods. The activation energies of the nanorods are much smaller than those of the bulk crystals of C60, indicating easier carrier injection of the fcc nanorods and their potential applications for the fabrication of efficient nanodevices. The good operational stability of individual C60nanorod based devices under sustained high dc voltage suggested their application as stable units in micro electronics or chemical sensor systems.

Eco-friendly visible-wavelength photodetectors based on bandgap engineerable nanomaterials

Co-reporter:Jian-Jun Wang, Jin-Song Hu, Yu-Guo Guo and Li-Jun Wan

Journal of Materials Chemistry A 2011 - vol. 21(Issue 44) pp:NaN17589-17589

Publication Date(Web):2011/09/22

DOI:10.1039/C1JM12173A

The development of visible-wavelength photodetectors based on eco-friendly and bandgap engineerable nanomaterials represents an important and promising direction in photodetector study. This highlight reviewed the recent progress in the design and construction of photodetectors based on the environmentally friendly binary metal chalcogenides and bandgap-tunable ternary or quaternary compounds such as InSe, In2Se3, ZrS2, Sb2Se3, and CuInSe2etc. Most photodetectors exhibit high sensitivity, fast photoresponse and good stability, benefiting from increased carrier mobility or improved carrier separation. We believe that the continuous effort in this direction will produce promising and practicable photodetectors and may open up new insight into the design of controllable photodetectors and their potential applications in new fields.

Core–shell structured Ce2S3@ZnO and its potential as a pigment

Co-reporter:Wen-Xin Mao, Wei Zhang, Zi-Xiang Chi, Rong-Wen Lu, An-Min Cao and Li-Jun Wan

Journal of Materials Chemistry A 2015 - vol. 3(Issue 5) pp:NaN2180-2180

Publication Date(Web):2014/11/26

DOI:10.1039/C4TA05797J

The potential use of cerium selenide (Ce2S3) as a non-toxic pigment has long been plagued by its release of hydrogen sulfide (H2S). Here, it is shown that a uniform nanoshell of zinc oxide (ZnO) can effectively eliminate the released H2S and also improve the thermal stability of Ce2S3. Through a series of investigations, a 40 nm thick ZnO surface coating layer was found to provide full protection for the Ce2S3 core, and this thickness is best for eliminating the release of H2S. Such a core–shell configuration has great potential for real applications of Ce2S3 as an odorless and non-toxic inorganic pigment.

TNT adsorption on Au(111): electrochemistry and adlayer structure

Co-reporter:Rui Wen, Hong-Xia Zhang, Cun-Ji Yan, Hui-Juan Yan, Ge-Bo Pan and Li-Jun Wan

Chemical Communications 2008(Issue 16) pp:NaN1879-1879

Publication Date(Web):2008/03/18

DOI:10.1039/B719888D

Electrochemistry and adlayer structure of trinitrotoluene (TNT) on an Au(111) electrode were investigated using cyclic voltammetry and in situ electrochemical scanning tunneling microscopy (ECSTM).

Enhanced stability and activity with Pd–O junction formation and electronic structure modification of palladium nanoparticles supported on exfoliated montmorillonite for the oxygen reduction reaction

Co-reporter:W. Ding, M.-R. Xia, Z.-D. Wei, S.-G. Chen, J.-S. Hu, L.-J. Wan, X.-Q. Qi, X.-H. Hu and L. Li

Chemical Communications 2014 - vol. 50(Issue 50) pp:NaN6663-6663

Publication Date(Web):2014/05/02

DOI:10.1039/C4CC02180K

Palladium has been the focus of recent research on alternative Pt catalysts for the oxygen reduction reaction (ORR). We show that the activity and stability of Pd toward the ORR can be enhanced by Pd–O-oxide covalent bonding when Pd is supported on exfoliated montmorillonite (ex-MMT) nanoplatelets.

Controlled formation of uniform nanoshells of manganese oxide and their potential in lithium ion batteries

Co-reporter:Xiao-Chan Liu, Jun-Yu Piao, De-Shan Bin, Tian-Qi Zhang, Shu-Yi Duan, Zi-Xiao Wu, An-Min Cao and Li-Jun Wan

Chemical Communications 2017 - vol. 53(Issue 19) pp:NaN2849-2849

Publication Date(Web):2017/02/08

DOI:10.1039/C7CC00284J

Uniform nanoshells of manganese oxides have been successfully prepared by controlling their growth kinetics in solution. The prepared manganese oxides show promising electrochemical performance when used as an anode material in lithium ion batteries.

The intramolecular H-bonding effect on the growth and stability of Schiff-base surface covalent organic frameworks

Co-reporter:Yi-Ping Mo, Xuan-He Liu, Bing Sun, Hui-Juan Yan, Dong Wang and Li-Jun Wan

Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 1) pp:NaN543-543

Publication Date(Web):2016/11/23

DOI:10.1039/C6CP06894D

The introduction of intramolecular H-bonding by adding –OH functionalities adjacent to the Schiff base centers is considered to be a useful strategy to enhance the stability and crystallinity of bulk covalent organic frameworks (COFs). However, the influence of intramolecular H-bonding on the synthesis of surface COFs (SCOFs) have been barely explored. Herein, SCOFs based on the Schiff-base reaction between 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehydes with symmetry or asymmetrically substituted hydroxyl functional groups are designed. In the absence of a solvent, hydroxyl substituents can be easily oxidized; thus argon protection is required to obtain high-quality SCOFs. Besides, an extended network with uniform pores can be achieved in spite of the symmetry of substituents. Both experimental results and theoretical calculations show that the influence of intramolecular hydrogen bonding on surface synthesis is not as important as that in bulk phase synthesis because the substrate itself can lead to the complanation of adsorbed molecules. The existence of intramolecular H-bonding can enhance the stability of the network in both acid and alkali environments.

Controlled formation of uniform CeO2 nanoshells in a buffer solution

Co-reporter:Wei Zhang, Li-Ping Yang, Zi-Xiao Wu, Jun-Yu Piao, An-Min Cao and Li-Jun Wan

Chemical Communications 2016 - vol. 52(Issue 7) pp:NaN1423-1423

Publication Date(Web):2015/11/23

DOI:10.1039/C5CC08422A

Uniform CeO2 nanoshells were successfully prepared by using buffer solution as a unique growth medium. The application of this methodology to construct a yolk–shell structured Au@CeO2 nanocatalyst shows improved performance for the catalytic CO oxidation.

The formation of an ordered microporous aluminum-based material mediated by phthalic acid

Co-reporter:Wei Zhang, Jian-Hua Cai, Pei-Pei Huang, Lin-Lin Hu, An-Min Cao and Li-Jun Wan

Chemical Communications 2016 - vol. 52(Issue 51) pp:NaN8041-8041

Publication Date(Web):2016/05/31

DOI:10.1039/C6CC01667G

By using phthalic acid as a soft template, we showed that it was possible to prepare a microporous aluminum-based material when the precipitation of Al3+ was properly controlled. We also identified that this microporous aluminum-based material could be promising for the removal of fluoride ions in water treatment.

Core–shell structured TiO2@polydopamine for highly active visible-light photocatalysis

Co-reporter:Wen-Xin Mao, Xi-Jie Lin, Wei Zhang, Zi-Xiang Chi, Rong-Wen Lyu, An-Min Cao and Li-Jun Wan

Chemical Communications 2016 - vol. 52(Issue 44) pp:NaN7125-7125

Publication Date(Web):2016/04/28

DOI:10.1039/C6CC02041K

This communication reports that the TiO2@polydopamine nanocomposite with a core–shell structure could be a highly active photocatalyst working under visible light. A very thin layer of polydopamine at around 1 nm was found to be critical for the degradation of Rhodamine B.

Controlled formation of core–shell structures with uniform AlPO4 nanoshells

Co-reporter:Fen-Li Yang, Wei Zhang, Zi-Xiang Chi, Fu-Quan Cheng, Ji-Tao Chen, An-Min Cao and Li-Jun Wan

Chemical Communications 2015 - vol. 51(Issue 14) pp:NaN2945-2945

Publication Date(Web):2015/01/09

DOI:10.1039/C4CC09924A

Uniform AlPO4 nanoshells are successfully achieved on different core materials by controlling their formation kinetics in solution. The application of this coating protocol to LiCoO2 shows an obvious improvement in its battery performance.

In situ encapsulation of Pd inside the MCM-41 channel

Co-reporter:Xi-Jie Lin, Ai-Zhi Zhong, Yong-Bin Sun, Xing Zhang, Wei-Guo Song, Rong-Wen Lu, An-Min Cao and Li-Jun Wan

Chemical Communications 2015 - vol. 51(Issue 35) pp:NaN7485-7485

Publication Date(Web):2015/03/24

DOI:10.1039/C5CC00300H

Pd nanoparticles were successfully introduced into the channels of mesoporous silica MCM-41 with their dispersion well-tuned. We identified the dual role played by CTAB, which was critical for both the micelle template and Pd grafting, leading to the formation of a highly active Pd–MCM-41 nanocomposite for catalysing the Suzuki reaction.

Unexpected functions of oxygen in a chemical vapor deposition atmosphere to regulate graphene growth modes

Co-reporter:Jing Li, Dong Wang and Li-Jun Wan

Chemical Communications 2015 - vol. 51(Issue 85) pp:NaN15489-15489

Publication Date(Web):2015/08/26

DOI:10.1039/C5CC06073G

Herein, by controlling the oxygen concentration in a graphene growth process, we reveal that the ppm grade of oxygen in the graphene growth atmosphere can tune the graphene growth modes of multilayer growth and graphene etching fragments.

Controllable atmospheric pressure growth of mono-layer, bi-layer and tri-layer graphene

Co-reporter:Jing Li, Hengxing Ji, Xing Zhang, Xuanyun Wang, Zhi Jin, Dong Wang and Li-Jun Wan

Chemical Communications 2014 - vol. 50(Issue 75) pp:NaN11015-11015

Publication Date(Web):2014/07/28

DOI:10.1039/C4CC04928D

Here we report a three-step growth method for high-quality mono-layer, bi-layer and tri-layer graphene with coverage ∼90% at atmospheric pressure. The growth temperature and gas flow rate have been found to be the key factors. This method would be of great importance for the large scale production of graphene with defined thickness.

Construction and repair of highly ordered 2D covalent networks by chemical equilibrium regulation

Co-reporter:Cui-Zhong Guan, Dong Wang and Li-Jun Wan

Chemical Communications 2012 - vol. 48(Issue 24) pp:NaN2945-2945

Publication Date(Web):2011/12/14

DOI:10.1039/C2CC16892H

The construction of well-ordered 2D covalent networks via the dehydration of di-borate aromatic molecules was successfully realized through introducing a small amount of water into a closed reaction system to regulate the chemical equilibrium.

Hanging Pt hollow nanocrystal assemblies on graphene resulting in an enhanced electrocatalyst

Co-reporter:Yu-Ping Xiao, Shuo Wan, Xing Zhang, Jin-Song Hu, Zi-Dong Wei and Li-Jun Wan

Chemical Communications 2012 - vol. 48(Issue 83) pp:NaN10333-10333

Publication Date(Web):2012/08/17

DOI:10.1039/C2CC35562K

Pt hollow nanostructures assembled by nanocrystals were in situ grown and hung onto graphene layers to combine the merits from favorable catalyst morphology control and synergetic improvement effect of the graphene support, resulting in a composite with enhanced electrocatalytic performance.

Linear dislocation tunes chirality: STM study of chiral transition and amplification in a molecular assembly on an HOPG surface

Co-reporter:Ting Chen, Qing Chen, Ge-Bo Pan, Li-Jun Wan, Qi-Long Zhou and Rong-Ben Zhang

Chemical Communications 2009(Issue 19) pp:NaN2651-2651

Publication Date(Web):2009/02/11

DOI:10.1039/B817525J

Molecular arrangement and transition in the domain boundary of a chiral two-dimensional assembly is clearly revealed by high-resolution STM images on an HOPG surface and a linear dislocation formed by molecular trimers and located at opposite chiral domains is found to directly reverse the chirality on DTCD self-assembly.

Donor/acceptor complex of triphenylene and trinitrotoluene on Au(111): a scanning tunneling microscopy study

Co-reporter:Rui Wen, Cun-Ji Yan, Hui-Juan Yan, Ge-Bo Pan and Li-Jun Wan

Chemical Communications 2011 - vol. 47(Issue 24) pp:NaN6917-6917

Publication Date(Web):2011/05/19

DOI:10.1039/C1CC11358E

The co-adsorption of trinitrotoluene (TNT), a typical π-electron acceptor, and triphenylene (TP), a typical π-electron donor, on a Au(111) surface was investigated by in situ Electrochemical Scanning Tunneling Microscopy (ECSTM). DFT calculations proved that parallelly stacked and well-overlapped TP and TNT molecules can form Donor–Acceptor dyads through intermolecular π–π charge transfer, which agree well with the experimental results in the present work.

Facile synthesis of nanoporous anatase spheres and their environmental applications

Co-reporter:Liang-Shu Zhong, Jin-Song Hu, Li-Jun Wan and Wei-Guo Song

Chemical Communications 2008(Issue 10) pp:NaN1186-1186

Publication Date(Web):2008/01/11

DOI:10.1039/B718300C

Highly nanoporous TiO2 (anatase) spheres with an excellent ability in environmental applications have been successfully prepared viain situhydrolysis of titanium glycolate precursor spheres.

ZnOEP based phototransistor: signal amplification and light-controlled switch

Co-reporter:Heng-Xing Ji, Jin-Song Hu and Li-Jun Wan

Chemical Communications 2008(Issue 23) pp:NaN2655-2655

Publication Date(Web):2008/05/15

DOI:10.1039/B805204B

A phototransistor with a field-effect transistor configuration was fabricated using a single zinc octaethylporphyrin (ZnOEP) nanorod; the device showed ability in signal amplification and reversible light-controlled switching.

Facile solution synthesis of hexagonal Alq3 nanorods and their field emission properties

Co-reporter:Jin-Song Hu, Heng-Xing Ji, An-Min Cao, Zheng-Xi Huang, Yang Zhang, Li-Jun Wan, An-Dong Xia, Da-Peng Yu, Xiang-Min Meng and Shuit-Tong Lee

Chemical Communications 2007(Issue 29) pp:NaN3085-3085

Publication Date(Web):2007/05/17

DOI:10.1039/B704106C

A facile self-assembly growth route assisted by surfactant has been developed to synthesize tris(8-hydroxyquinoline)aluminium (Alq3) nanorods with regular hexagonal shape and good crystallinity, which exhibit field-emission characteristics with a very low turn-on field of ca. 3.1 V µm−1 and a high field-enhancement factor of ca. 1300.

Physical vapor deposition of amorphous MoS2 nanosheet arrays on carbon cloth for highly reproducible large-area electrocatalysts for the hydrogen evolution reaction

Co-reporter:Xing Zhang, Yun Zhang, Bin-Bin Yu, Xing-Liang Yin, Wen-Jie Jiang, Yan Jiang, Jin-Song Hu and Li-Jun Wan

Journal of Materials Chemistry A 2015 - vol. 3(Issue 38) pp:NaN19281-19281

Publication Date(Web):2015/08/25

DOI:10.1039/C5TA05793K

Molybdenum sulfide materials have been shown to be promising non-precious metal catalysts for the hydrogen evolution reaction (HER). This work reports a facile and scalable preparation method for amorphous MoS2 nanosheet arrays directly deposited on carbon cloth (a-MoS2 NA/CC) using a highly reproducible physical vapor deposition (PVD) approach. As a result of the three-dimensional nanostructure of the catalyst, the amorphous nature and the abundant exposed edge sites of MoS2, the a-MoS2 NA/CC composite exhibited superior catalytic activity and stability for the HER in acidic solutions.

In situ nitrogen-doped nanoporous carbon nanocables as an efficient metal-free catalyst for oxygen reduction reaction

Co-reporter:Wen-Jie Jiang, Jin-Song Hu, Xing Zhang, Yan Jiang, Bin-Bin Yu, Zi-Dong Wei and Li-Jun Wan

Journal of Materials Chemistry A 2014 - vol. 2(Issue 26) pp:NaN10160-10160

Publication Date(Web):2014/04/23

DOI:10.1039/C4TA01780C

A new N-doped carbon nanomaterial with nanoporous coaxial nanocable structure was designed for achieving the requirements of high nitrogen content, proper nitrogen bonding state, and sufficient electron and mass transportation for an oxygen reduction reaction (ORR) catalyst. The nanoporous sheaths provided more catalytic sites and allowed oxygen and reactants to easily access them for fast mass transfer, whereas carbon nanotube cores provided a three-dimensional conductive network and guaranteed fast electron transfer. As a result, the designed low-cost catalyst exhibited excellent electrocatalytic performance and is one of the most active metal-free ORR catalyst.

Accurate surface control of core–shell structured LiMn0.5Fe0.5PO4@C for improved battery performance

Co-reporter:Zi-Xiang Chi, Wei Zhang, Xu-Sheng Wang, Fu-Quan Cheng, Ji-Tao Chen, An-Min Cao and Li-Jun Wan

Journal of Materials Chemistry A 2014 - vol. 2(Issue 41) pp:NaN17365-17365

Publication Date(Web):2014/08/26

DOI:10.1039/C4TA03739A

Manganese-based mixed polyanion cathodes known as LiMn1−xFexPO4 can show much higher energy density as compared to the well-commercialized product of lithium iron phosphate. However, their much lower electronic conductivity has long plagued their further application. Here, by means of a facile solution-based synthesis route, we are able to introduce a uniform and conformal carbon coating layer onto LiMn1−xFexPO4 nanoparticles. The versatility in the synthesis control endows us with the capability of controlling the shell thickness with one nanometer accuracy, offering an effective way to optimize the battery performance through a systematic shell control. Detailed investigation reveals that the carbon nanoshells not only act as good electronic conducting media, but also contribute to the inhibition of the metal (Mn and Fe) dissolution and reduce the exothermic heat released during cycling. The core–shell structured cathode materials show promising potential for their application in lithium ion batteries as revealed by their high charge–discharge capacity, remarkable thermal stability, and excellent cyclability.

Pd-induced Pt(IV) reduction to form Pd@Pt/CNT core@shell catalyst for a more complete oxygen reduction

Co-reporter:Meirong Xia, Ying Liu, Zidong Wei, Siguo Chen, Kun Xiong, Li Li, Wei Ding, Jinsong Hu, Li-Jun Wan, Rong Li and Shahnaz Fatima Alvia

Journal of Materials Chemistry A 2013 - vol. 1(Issue 46) pp:NaN14448-14448

Publication Date(Web):2013/09/27

DOI:10.1039/C3TA13139D

We describe a facile and controllable process for preparing Pd@Pt/CNT core@shell catalysts for the oxygen reduction reaction (ORR) via Pd-induced Pt(IV) reduction on Pd/CNT. The mass-specific activity for the ORR of the Pd@Pt/CNT catalysts is 7–9 times higher than that of the state-of-the-art Pt/C catalysts, but the yield of H2O2, a harmful species for the stability of catalysts, of the former is only 14.1% of that of the latter. The reason for the enhanced activity and the lower H2O2 yield on the Pd@Pt/CNT catalysts was studied by DFT calculations.

In vitro and in vivo photothermally enhanced chemotherapy by single-walled carbon nanohorns as a drug delivery system

Co-reporter:Daiqin Chen, Chao Wang, Feng Jiang, Zhuang Liu, Chunying Shu and Li-Jun Wan

Journal of Materials Chemistry A 2014 - vol. 2(Issue 29) pp:NaN4732-4732

Publication Date(Web):2014/04/23

DOI:10.1039/C4TB00249K

Single-walled carbon nanohorns (SWNHs) have exhibited many special advantages in biomedical applications. Herein, doxorubicin-loaded SWNHs (DOX-SWNHs) are prepared and further modified by amphiphilic deoxycholic acid modified-hydropropyl chitosan (DCA-HPCHS) to improve their biocompatibility. The obtained DOX-SWNH/DCA-HPCHS drug delivery system (DDS) possesses high stability in physiological media and excellent photothermal properties when exposed to laser irradiation in the near-infrared (NIR) region, which dramatically enhances the chemotherapy of DOX. Cell viability assays show that the growth of 4T1 cells are remarkably inhibitory under the conditions of incubation with DOX-SWNH/DCA-HPCHS and subsequent exposure to 808 nm laser irradiation to produce mild photothermal heating to 43 °C. Further investigation reveals that the photothermally enhanced chemotherapy derived from a promotion of DOX-SWNH/DCA-HPCHS uptake by the cancer cells rather than a light-triggered release of DOX. DOX-SWNH/DCA-HPCHS in combination with the use of laser irradiation exhibits a much better anticancer effect than the controls. Hence, the DOX-SWNH/DCA-HPCHS as a multifunctional DDS has been proposed and is hopeful for medicinal use in the future.

Facile growth of centimeter-sized single-crystal graphene on copper foil at atmospheric pressure

Co-reporter:Jing Li, Xuan-Yun Wang, Xing-Rui Liu, Zhi Jin, Dong Wang and Li-Jun Wan

Journal of Materials Chemistry A 2015 - vol. 3(Issue 15) pp:NaN3535-3535

Publication Date(Web):2015/02/18

DOI:10.1039/C5TC00235D

By mildly oxidizing Cu foil and slowing down the total gas flow rate, we develop an easily repeatable atmospheric growth method to grow single-crystal graphene of centimeter-size. The graphene edge, which is different from the previously reported straight edge, is connected by a series of graphene-corners. The graphene-corner, ranging between 100° and 110°, is formed by a zig-zag edge and a mix edge. The oxidation of Cu crystal boundaries results in the rearrangement of active Cu sites for graphene nucleation, thus suppressing graphene nucleation density.

Fabrication of bilayer tetrathiafulvalene integrated surface covalent organic frameworks

Co-reporter:Wei-Long Dong, Shu-Ying Li, Jie-Yu Yue, Cheng Wang, Dong Wang and Li-Jun Wan

Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 26) pp:NaN17359-17359

Publication Date(Web):2016/06/06

DOI:10.1039/C6CP01804A

A bilayer covalent organic framework (COF) of TTF-based building blocks was obtained by imine reaction between tetrathiafulvalene tetraaldehyde (4ATTF) and p-phenylenediamine (PPDA). Direct evidence for the eclipsed stacking of bilayer structure via π–π interaction between TTF units is provided by high resolution scanning tunneling microscopy.

Initial solid electrolyte interphase formation process of graphite anode in LiPF6 electrolyte: an in situ ECSTM investigation

Co-reporter:Lin Wang, Xin Deng, Pei-Xia Dai, Yu-Guo Guo, Dong Wang and Li-Jun Wan

Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 20) pp:NaN7336-7336

Publication Date(Web):2012/04/05

DOI:10.1039/C2CP40595D

Understanding the structure and formation dynamics of the solid electrolyte interphase (SEI) on the electrode/electrolyte interface is of great importance for lithium ion batteries, as the properties of the SEI remarkably affect the performances of lithium ion batteries such as power capabilities, cycling life, and safety issues. Herein, we report an in situ electrochemical scanning tunnelling microscopy (ECSTM) study of the surface morphology changes of a highly oriented pyrolytic graphite (HOPG) anode during initial lithium uptake in 1 M LiPF6 dissolved in the solvents of ethylene carbonate plus dimethyl carbonate. The exfoliation of the graphite originating from the step edge occurs when the potential is more negative than 1.5 V vs. Li+/Li. Within the range from 0.8 to 0.7 V vs. Li+/Li, the growth of clusters on the step edge, the decoration of the terrace with small island-like clusters, and the exfoliation of graphite layers take place on the surface simultaneously. The surface morphology change in the initial lithium uptake process can be recovered when the potential is switched back to 2.0 V. Control experiments indicate that the surface morphology change can be attributed to the electrochemical reduction of solvent molecules. The findings may lead to a better understanding of SEI formation on graphite anodes, optimized electrolyte systems for it, as well as the use of in situ ECSTM for interface studies in lithium ion batteries.

Wet chemical synthesis of Cu/TiO2 nanocomposites with integrated nano-current-collectors as high-rate anode materials in lithium-ion batteries

Co-reporter:Fei-Fei Cao, Sen Xin, Yu-Guo Guo and Li-Jun Wan

Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 6) pp:NaN2020-2020

Publication Date(Web):2011/01/04

DOI:10.1039/C0CP01119C

Using a soft-template assisted method, well-organized Cu/TiO2 nanoarchitectured electrode materials with copper nanowires as their own current collectors are synthesized by controlled hydrolysis of tetrabutyl titanate in the presence of Cu-based nanowires, and investigated by SEM, TEM, XRD, Raman spectroscopy and electrochemical tests towards lithium storage. Two types of Cu/TiO2 nanocomposites with different TiO2 grain sizes are obtained by using different thermal treatments. The two types of Cu/TiO2 nanocomposites show much enhanced rate performances compared with bare TiO2. A high-rate capability (reversible capacity at 7500 mA g−1 still accounts for 58% of its initial capacity at 50 mA g−1) is observed for the Cu/TiO2 nanocomposite with smaller TiO2 grain size. The improvements can be attributed to the integrated Cu nanowires as mechanical supports and efficient current collectors. A cell made from the Cu/TiO2 nanoarchitectured electrodes exhibits promise as an energy storage device with both high energy and high power densities.

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