Co-reporter:Chongyi Ling;Li Shi;Yixin Ouyang
Chemistry of Materials December 27, 2016 Volume 28(Issue 24) pp:9026-9032
Publication Date(Web):November 28, 2016
DOI:10.1021/acs.chemmater.6b03972
Co-reporter:Yinghe Zhao and Jinlan Wang
The Journal of Physical Chemistry C 2017 Volume 121(Issue 8) pp:
Publication Date(Web):February 14, 2017
DOI:10.1021/acs.jpcc.7b00606
Organic/inorganic interfaces play dominant roles in the formation of organic thin films and the performance of organic electronic devices. Preparing a high-quality and high-stability interfacial organic layer on the inorganic substrate is currently challenging, and understanding the self-assembly mechanism of the interfacial layer (IL) in depth at a molecular level is thus essential. In this work, by studying the self-assembly of perylene-3,4,9,10-tetracarboxylic dianhydride IL on graphene, we unveil that intermolecular H-bonds can considerably widen the nucleation area, heighten the stability–metastability critical temperature, promote the nucleation speed, and guide the nucleation direction. We further demonstrate that such positive effects on the IL self-assembly are of generality. Moreover, it is found that IL can transform into a well-ordered crystal from an amorphous state through suitable thermal treatment or molecule coverage control. Our work highlights that fabricating H-bond networks is desirable for the synthesis of robust and high-quality IL and points out feasible routes to improve the quality of poor IL.
Co-reporter:Xianghong NiuYunhai Li, Huabing ShuXiaojing Yao, Jinlan Wang
The Journal of Physical Chemistry C 2017 Volume 121(Issue 6) pp:
Publication Date(Web):January 24, 2017
DOI:10.1021/acs.jpcc.6b12613
Efficient carrier separation is the key to the application of photoelectric device. However, photogenerated electron–hole pairs in simplex semiconductors generally occupy the same regions spatially and are easy to recombine. Here we design a graphitic zinc-oxide-based (g-ZnO) intrinsic type-II heterostructure, g-ZnO/blue phosphorus (BP), based on first-principles calculations. The type-II band offsets and large built-in electric field ensure the photogenerated electrons easily migrating from g-ZnO to BP, which significantly enhances the separation of electron–hole pairs. Improved optical absorption is also observed in the heterostructure. Furthermore, the perpendicular external electric field can greatly modulate band edges and achieve a direct band gap at Γ point, which provides further promotion in the separation of carriers.
Co-reporter:Xiaojing Yao;Gang Wu;Shermin S. Goh;Hongjun Zhu;Shuo-Wang Yang
Journal of Materials Chemistry C 2017 vol. 5(Issue 14) pp:3585-3591
Publication Date(Web):2017/04/06
DOI:10.1039/C7TC00678K
Based on density functional theory (DFT) calculations, we studied a two-step surface reaction for fabricating conductive molecular wires on hydrogen-terminated Si(100)2 × 1 surfaces. The first step is the self-assembled growth of 1,3,5-triethynylbenzene (TEB) molecules and formation of aligned molecular arrays on a H–Si(100)2 × 1 surface, and the second step is the in situ polymerization of the adsorbed molecules with CO via formal [2 + 2 + 1] cycloaddition reactions to produce a surface-grafted molecular wire, which is chemically bonded to the Si surface and electronically interlinked. The newly formed polymer/Si(100)2 × 1 structure is semiconducting and can be tuned to be conductive by electron doping; in this structure the molecular wires are the sole conducting channels and the Si substrate retains its semiconducting characteristics. Such unique properties make these surface-grafted molecular wires or polymers potential candidates in molecular electronics.
Co-reporter:Li Shi;Chongyi Ling;Yixin Ouyang
Nanoscale (2009-Present) 2017 vol. 9(Issue 2) pp:533-537
Publication Date(Web):2017/01/05
DOI:10.1039/C6NR06621F
Two-dimensional (2D) boron monolayers have been successfully synthesized on a silver substrate very recently. Their potential application is thus of great significance. In this work, we explore the possibility of boron monolayers (BMs) as electrocatalysts for the hydrogen evolution reaction (HER) by first-principles methods. Our calculations show that BMs are active catalysts for HER with nearly zero free energy of hydrogen adsorption, metallic conductivity and plenty of active sites in the basal plane. The effect of the substrate on HER activity is further assessed. It is found that the substrate has a positive effect on the HER performance caused by the competitive effect of mismatch strain and charge transfer. The in-depth understanding of the structure dependent HER activity is also provided.
Co-reporter:Dr. Qiang Li;Yinghe Zhao;Chongyi Ling;Dr. Shijun Yuan;Dr. Qian Chen; Jinlan Wang
Angewandte Chemie 2017 Volume 129(Issue 35) pp:10637-10641
Publication Date(Web):2017/08/21
DOI:10.1002/ange.201706038
AbstractSulfur vacancies (SVs) inherent in MoS2 are generally detrimental for carrier mobility and optical properties. Thiol chemistry has been explored for SV repair and surface functionalization. However, the resultant products and reaction mechanisms are still controversial. Herein, a comprehensive understanding on the reactions is provided by tracking potential energy surfaces and kinetic studies. The reactions are dominated by two competitive mechanisms that lead to either functionalization products or repair SVs, and the polarization effect from decorating thiol molecules and thermal effect are two determining factors. Electron-donating groups are conducive to the repairing reaction whereas electron-withdrawing groups facilitate the functionalization process. Moreover, the predominant reaction mechanism can be switched by increasing the temperature. This study fosters a way of precisely tailoring the electronic and optical properties of MoS2 by means of thiol chemistry approaches.
Co-reporter:Zehua Hu;Dr. Qiang Li;Bo Lei;Qionghua Zhou;Dr. Du Xiang;Dr. Zhiyang Lyu;Dr. Fang Hu;Junyong Wang;Yinjuan Ren;Rui Guo; Eda Goki; Li Wang;Dr. Cheng Han; Jinlan Wang; Wei Chen
Angewandte Chemie 2017 Volume 129(Issue 31) pp:9259-9263
Publication Date(Web):2017/07/24
DOI:10.1002/ange.201705012
AbstractBlack phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.
Co-reporter:Dr. Qiang Li;Yinghe Zhao;Chongyi Ling;Dr. Shijun Yuan;Dr. Qian Chen; Jinlan Wang
Angewandte Chemie International Edition 2017 Volume 56(Issue 35) pp:10501-10505
Publication Date(Web):2017/08/21
DOI:10.1002/anie.201706038
AbstractSulfur vacancies (SVs) inherent in MoS2 are generally detrimental for carrier mobility and optical properties. Thiol chemistry has been explored for SV repair and surface functionalization. However, the resultant products and reaction mechanisms are still controversial. Herein, a comprehensive understanding on the reactions is provided by tracking potential energy surfaces and kinetic studies. The reactions are dominated by two competitive mechanisms that lead to either functionalization products or repair SVs, and the polarization effect from decorating thiol molecules and thermal effect are two determining factors. Electron-donating groups are conducive to the repairing reaction whereas electron-withdrawing groups facilitate the functionalization process. Moreover, the predominant reaction mechanism can be switched by increasing the temperature. This study fosters a way of precisely tailoring the electronic and optical properties of MoS2 by means of thiol chemistry approaches.
Co-reporter:Zehua Hu;Dr. Qiang Li;Bo Lei;Qionghua Zhou;Dr. Du Xiang;Dr. Zhiyang Lyu;Dr. Fang Hu;Junyong Wang;Yinjuan Ren;Rui Guo; Eda Goki; Li Wang;Dr. Cheng Han; Jinlan Wang; Wei Chen
Angewandte Chemie International Edition 2017 Volume 56(Issue 31) pp:9131-9135
Publication Date(Web):2017/07/24
DOI:10.1002/anie.201705012
AbstractBlack phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.
Co-reporter:Yinghe Zhao;Qiang Li;Li Shi
Advanced Science 2017 Volume 4(Issue 12) pp:
Publication Date(Web):2017/12/01
DOI:10.1002/advs.201700356
AbstractThe development of nonprecious electrochemical catalysts for water splitting is a key step to achieve a sustainable energy supply for the future. Molybdenum disulfide (MoS2) has been extensively studied as a promising low-cost catalyst for hydrogen evolution reaction (HER), whereas HER is only catalyzed at the edge for pristine MoS2, leaving a large area of basal plane useless. Herein, on-surface self-assembly is demonstrated to be an effective, facile, and damage-free method to take full advantage of the large ratio surface of MoS2 for HER by using multiscale simulations. It is found that as supplement of edge sites of MoS2, on-MoS2 M(abt)2 (M = Ni, Co; abt = 2-aminobenzenethiolate) owns high HER activity, and the self-assembled M(abt)2 monolayers on MoS2 can be obtained through a simple liquid-deposition method. More importantly, on-surface self-assembly provides potential application for overall water splitting once the self-assembled systems prove to be of both HER and oxygen evolution reaction activities, for example, on-MoS2 Co(abt)2. This work opens up a new and promising avenue (on-surface self-assembly) toward the full exploitation of the basal plane of MoS2 for HER and the preparation of bifunctional catalysts for overall water splitting.
Co-reporter:Qionghua Zhou;Qiang Li;Shijun Yuan;Qian Chen
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 43) pp:29232-29236
Publication Date(Web):2017/11/08
DOI:10.1039/C7CP05730J
The poor environmental stability of black phosphorous (BP) seriously limits its practical applications in (opto)electronics. Other than capping protective layers on its surface, herein we propose a new strategy to improve BP's ambient stability by engineering the interlayer interactions. Our first-principles calculations demonstrate that enlarging the interlayer spacing can effectively shift the conduction band minimum down to suppress the generation of superoxide and the enlargement can be achieved by intercalating small molecules like H2 and He into BP. Moreover, the molecule intercalated BP maintains high hole mobility, which makes it a better two-dimensional semiconductor for practical applications.
Co-reporter:Bing Wang;Shijun Yuan;Yunhai Li;Li Shi
Nanoscale (2009-Present) 2017 vol. 9(Issue 17) pp:5577-5582
Publication Date(Web):2017/05/04
DOI:10.1039/C7NR00455A
Two-dimensional (2D) materials with Dirac cones exhibit rich physics and many intriguing properties, but the search for new 2D Dirac materials is still a current hotspot. Using the global particle-swarm optimization method and density functional theory, we predict a new stable graphene-like 2D Dirac material: a Be3C2 monolayer with a hexagonal honeycomb structure. The Dirac point occurs exactly at the Fermi level and arises from the merging of the hybridized pz bands of Be and C atoms. Most interestingly, this monolayer exhibits a high Fermi velocity in the same order of graphene. Moreover, the Dirac cone is very robust and retains even included spin–orbit coupling or external strain. These outstanding properties render the Be3C2 monolayer a promising 2D material for special electronics applications.
Co-reporter:Qisheng Wu;Wen Wu Xu;Bingyan Qu;Liang Ma;Xianghong Niu;Xiao Cheng Zeng
Materials Horizons (2014-Present) 2017 vol. 4(Issue 6) pp:1085-1091
Publication Date(Web):2017/10/30
DOI:10.1039/C7MH00461C
Gold–sulfur interfaces, including self-assembled monolayers of thiol molecules on gold surfaces, thiolate-protected gold nanoclusters, and gold sulfide complexes, have attracted intensive interest due to their promising applications in electrochemistry, bioengineering, and nanocatalysis. Herein, we predict two hitherto unreported two-dimensional (2D) Au6S2 monolayer polymorphs, named as G-Au6S2 and T-Au6S2. The global-minimum G-Au6S2 monolayer can be viewed as a series of [–S–Au–]n and [–Au4–]n chains packed together in parallel. The metastable T-Au6S2 monolayer resembles the widely studied T-MoS2 monolayer structure with each Mo atom substituted with an octahedral Au6 cluster, while the S atom is bonded with three Au atoms in a μ3 bridging mode. The G-Au6S2 monolayer is predicted to be metallic. The T-Au6S2 monolayer is predicted to be a semiconductor with a direct bandgap of 1.48 eV and high carrier mobility of 2721 cm2 V−1 s−1, ∼10 times higher than that of semiconducting H-MoS2. Moreover, the T-Au6S2 monolayer can absorb sunlight efficiently over almost the entire solar spectrum. These properties render the G- and T-Au6S2 monolayers promising materials for advanced applications in microelectronics and optoelectronics.
Co-reporter:Bing Wu, Yinghe Zhao, Haiyan Nan, Ziyi Yang, Yuhan Zhang, Huijuan Zhao, Daowei He, Zonglin Jiang, Xiaolong Liu, Yun Li, Yi Shi, Zhenhua Ni, Jinlan Wang, Jian-Bin Xu, and Xinran Wang
Nano Letters 2016 Volume 16(Issue 6) pp:3754-3759
Publication Date(Web):May 16, 2016
DOI:10.1021/acs.nanolett.6b01108
Precise assembly of semiconductor heterojunctions is the key to realize many optoelectronic devices. By exploiting the strong and tunable van der Waals (vdW) forces between graphene and organic small molecules, we demonstrate layer-by-layer epitaxy of ultrathin organic semiconductors and heterostructures with unprecedented precision with well-defined number of layers and self-limited characteristics. We further demonstrate organic p–n heterojunctions with molecularly flat interface, which exhibit excellent rectifying behavior and photovoltaic responses. The self-limited organic molecular beam epitaxy (SLOMBE) is generically applicable for many layered small-molecule semiconductors and may lead to advanced organic optoelectronic devices beyond bulk heterojunctions.
Co-reporter:Yixin Ouyang, Chongyi Ling, Qian Chen, Zilu Wang, Li Shi, and Jinlan Wang
Chemistry of Materials 2016 Volume 28(Issue 12) pp:4390
Publication Date(Web):May 27, 2016
DOI:10.1021/acs.chemmater.6b01395
Nanoscale molybdenum disulfide (MoS2) has attracted ever-growing interest as one of the most promising nonprecious catalysts for hydrogen evolution reaction (HER). However, the active sites of pristine MoS2 are located at the edges, leaving a large area of basal planes useless. Here, we systematically evaluate the capabilities of 16 kinds of structural defects including point defects (PDs) and grain boundaries (GBs) to activate the basal plane of MoS2 monolayer. Our first-principle calculations show that six types of defects (i.e., Vs, VMoS3, MoS2 PDs; 4|8a, S bridge, and Mo–Mo bond GBs) can greatly improve the HER performance of the in-plane domains of MoS2. More importantly, Vs and MoS2 PDs and S bridge and 4|8a GBs exhibit outstanding activity in both Heyrovsky and Tafel reactions as well. Moreover, the different HER activities of defects are well-understood by an amendatory band-center model, which is applicable to a broad class of systems with localized defect states. Our study provides a comprehensive picture of the defect-engineered HER activities of a MoS2 monolayer and opens a new window for optimizing the HER activity of two-dimensional dichalcogenides for future hydrogen utilization.
Co-reporter:Lei Xu, Qian Chen, Lei Liao, Xingqiang Liu, Ting-Chang Chang, Kuan-Chang Chang, Tsung-Ming Tsai, Changzhong Jiang, Jinlan Wang, and Jinchai Li
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 8) pp:5408
Publication Date(Web):February 9, 2016
DOI:10.1021/acsami.5b10220
Hydrogenation is one of the effective methods for improving the performance of ZnO thin film transistors (TFTs), which originate from the fact that hydrogen (H) acts as a defect passivator and a shallow n-type dopant in ZnO materials. However, passivation accompanied by an excessive H doping of the channel region of a ZnO TFT is undesirable because high carrier density leads to negative threshold voltages. Herein, we report that Mg/H codoping could overcome the trade-off between performance and reliability in the ZnO TFTs. The theoretical calculation suggests that the incorporation of Mg in hydrogenated ZnO decrease the formation energy of interstitial H and increase formation energy of O-vacancy (VO). The experimental results demonstrate that the existence of the diluted Mg in hydrogenated ZnO TFTs could be sufficient to boost up mobility from 10 to 32.2 cm2/(V s) at a low carrier density (∼2.0 × 1018 cm–3), which can be attributed to the decreased electron effective mass by surface band bending. The all results verified that the Mg/H codoping can significantly passivate the VO to improve device reliability and enhance mobility. Thus, this finding clearly points the way to realize high-performance metal oxide TFTs for low-cost, large-volume, flexible electronics.Keywords: hydrogenation; mobility; reliability; thin film transistors; ZnO
Co-reporter:Wenqing Liu, Qionghua Zhou, Qian Chen, Daxin Niu, Yan Zhou, Yongbing Xu, Rong Zhang, Jinlan Wang, and Gerrit van der Laan
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 9) pp:5752
Publication Date(Web):February 18, 2016
DOI:10.1021/acsami.5b11438
Understanding magnetism in ferromagnetic metal/semiconductor (FM/SC) heterostructures is important to the development of the new-generation spin field-effect transistor. Here, we report an element-specific X-ray magnetic circular dichroism study of the interfacial magnetic moments for two FM/SC model systems, namely, Co/GaAs and Ni/GaAs, which was enabled using a specially designed FM1/FM2/SC superstructure. We observed a robust room temperature magnetization of the interfacial Co, while that of the interfacial Ni was strongly diminished down to 5 K because of hybridization of the Ni d(eg) and GaAs sp3 states. The validity of the selected method was confirmed by first-principles calculations, showing only small deviations (<0.02 and <0.07 μB/atom for Co/GaAs and Ni/GaAs, respectively) compared to the real FM/SC interfaces. Our work proved that the electronic structure and magnetic ground state of the interfacial FM2 is not altered when the topmost FM2 is replaced by FM1 and that this model is applicable generally for probing the buried magnetic interfaces in the advanced spintronic materials..Keywords: interface; magnetic dead layer; spintronics; superstructure; XMCD
Co-reporter:Huabing Shu, Yunhai Li, Xianghong Niu, and Jinlan Wang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 20) pp:13150
Publication Date(Web):May 4, 2016
DOI:10.1021/acsami.6b03242
Structural defects in the molybdenum disulfide (MoS2) monolayer are widely reported and greatly degrade the transport and photoluminescence. However, how they influence the optical absorption properties remains unclear. In this work, by employing many-body perturbation theory calculations, we investigate the influence of sulfur vacancies (SVs), the main type of intrinsic defects in the MoS2 monolayer, on the optical absorption and exciton effect. Our calculations reveal that the presence of SVs creates localized midgap states in the bandgap, which results in a dramatic red-shift of the absorption peak and stronger absorbance in the visible light and near-infrared region. Nevertheless, the SVs can be finely repaired by oxygen passivation and are beneficial to the formation of the stable localized excitons, which greatly enhance the optical absorption in the spectral range. The defect-mediated/-engineered absorption mechanism is well understood, which offers insightful guides for improving the performance of two-dimensional dichalcogenide-based optoelectronic devices.Keywords: exciton; molybdenum disulfide; optical absorption; oxygen passivation; sulfur vacancies
Co-reporter:Wenxia Zhang, Xianghong Niu, Xifang Chen, Xiaoxiao Guo, Jinlan Wang, Jiyang Fan
Carbon 2016 Volume 109() pp:40-48
Publication Date(Web):November 2016
DOI:10.1016/j.carbon.2016.07.067
Carbon nanocrystals (NCs) exhibit very intricate luminescence and the underlying mechanism remains a mystery and highly debated. Herein we study the luminescence properties of the wet chemistry-derived diamond NCs and observe peculiar phenomenon of concurrent multiband luminescence across the whole visible region in them. The surface structural and luminescence investigation in conjunction with density functional theory calculation reveal fruitful oxygen-related surface defects in these diamond NCs, and such defects create respective energy levels in the band gap leading to observed luminescences. The calculation shows that these surface traps have either localized or delocalized molecular orbitals, and significant spatial overlap between the highest occupied and lowest unoccupied molecular orbitals of amide-terminated diamond NCs leads to extremely large radiative decay rate as well as unprecedented high quantum yield of 50.4%, in strong contrast with usually low quantum yield of 2.5–5.0% in oxygen-terminated diamond NCs. The result indicates these surface defects are popular and they play important roles in luminescence of the large family of various (graphite, diamond, and C8) carbon as well as SiC and C3N4 NCs.
Co-reporter:Xiaojing Yao, Xiuyun Zhang, Xiaoshan Ye and Jinlan Wang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 32) pp:22390-22398
Publication Date(Web):18 Jul 2016
DOI:10.1039/C6CP03705D
Tuning the electronic and magnetic properties of graphene is a crucial problem in the design of practical on–off electronic devices. Using density functional theory calculations, we explore the electronic and magnetic properties of bilayer graphene functionalized by cyclopentadienyl (Cp = cyclopentadienyl, C5H5) based half-sandwich ligands, CpTM (TM = Sc–Ni). It is found that the adsorption of CpTM ligands can introduce high magnetic moments and open the band gap of bilayer graphene, due to the electron doping as well as the asymmetric charge distribution between two graphene layers. Furthermore, the p–n doping of bilayer graphene by co-binding F/NO2 and CpTM on two external sides of BLG can further widen the band gap up to 366.1 meV. This study proposes an effective way to the modulation of the electronic and magnetic properties of graphene.
Co-reporter:Huabing Shu, Yunhai Li, Xianghong Niu and Jinlan Wang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 8) pp:6085-6091
Publication Date(Web):26 Jan 2016
DOI:10.1039/C5CP07995K
By employing density-functional theory, the G0W0 method and Bethe–Salpter equation, we explore quasi-particle energy bands, optical responses and excitons of bilayer black phosphorus (BBP) with four different stacking patterns. All the structures are direct band gap semiconductors and the band gap is highly dependent on the stacking pattern, with a maximum of 1.31 eV for AB-stacking and a minimum of 0.92 eV for AD-stacking. Such dependence can be well understood by the tight-binding model in terms of the interlayer hopping. More interestingly, stacking sensitive optical absorption and exciton binding energy are observed in BBPs. For x-polarized light, more red-shift of optical adsorption appears in AA-stacking and the strong exciton binding energy in the AA-stacking bilayer can be as large as 0.82 eV, that is ∼1.7 times larger than that of AD-stacking bilayer.
Co-reporter:Xianghong Niu; Yunhai Li; Huabing Shu
The Journal of Physical Chemistry Letters 2016 Volume 7(Issue 3) pp:370-375
Publication Date(Web):January 10, 2016
DOI:10.1021/acs.jpclett.5b02457
Understanding electron transitions in black phosphorus nanostructures plays a crucial role in applications in electronics and optoelectronics. In this work, by employing time-dependent density functional theory calculations, we systematically study the size-dependent electronic, optical absorption, and emission properties of black phosphorus quantum dots (BPQDs). Both the electronic gap and the absorption gap follow an inversely proportional law to the diameter of BPQDs in conformity to the quantum confinement effect. In contrast, the emission gap exhibits anomalous size dependence in the range of 0.8–1.8 nm, which is blue-shifted with the increase of size. The anomaly in fact arises from the structure distortion induced by the excited-state relaxation, and it leads to a huge Stokes shift in small BPQDs.
Co-reporter:Liyan Zhu, Jinlan Wang, and Feng Ding
ACS Nano 2016 Volume 10(Issue 6) pp:6410
Publication Date(Web):June 2, 2016
DOI:10.1021/acsnano.6b03231
It is widely believed that carbon nanotubes (CNTs) can be employed to produce superstrong materials with tensile strengths of up to 50 GPa. Numerous efforts have, however, led to CNT fibers with maximum strengths of only a few GPa. Here we report that, due to different mechanical responses to the tensile loading of disclination topological defects in the CNT walls, a few of these topological defects are able to greatly decrease the strength of the CNTs, by up to an order of magnitude. This study reveals that even nearly perfect CNTs cannot be used to build exceptionally strong materials, and therefore synthesizing flawless CNTs is essential for utilizing the ideal strength of CNTs.Keywords: carbon nanotubes; density functional tight binding; disclination topological defects; tensile strength
Co-reporter:Xiaojing Yao
The Journal of Physical Chemistry C 2016 Volume 120(Issue 13) pp:7088-7093
Publication Date(Web):March 22, 2016
DOI:10.1021/acs.jpcc.5b11660
The structural, electronic, and magnetic properties of two kinds of boron-doped europium cyclooctatetraene sandwich molecular wires (SMWs), [EuCOTB]∞ and [Eu-COTB-Eu-COT]∞ (Eu = europium, COT = cyclooctatetraene = C8H8, COTB = boratacyclooctatetraene), are investigated with spin-polarized density functional theory. Both SMWs are of high stability and ultrahigh magnetic moments, and the [Eu-COTB-Eu-COT]∞ SMW even owns half-metallic characteristics. Our calculations further reveal that the [Eu-COTB-Eu-COT]∞ SMW anchored on a semiconductor germanium surface is a quasi-half-metallic ferromagnet, and it can be tuned into full half-metallicity under a mild external electric field. The unveiled intriguing properties here suggest that the boron-doped europium cyclooctatetraene SMWs may be compelling candidates for future spintronics devices.
Co-reporter:Qiang Li, Qionghua Zhou, Xianghong Niu, Yinghe Zhao, Qian Chen, and Jinlan Wang
The Journal of Physical Chemistry Letters 2016 Volume 7(Issue 22) pp:4540-4546
Publication Date(Web):October 29, 2016
DOI:10.1021/acs.jpclett.6b02192
The chemical functionalization is proven to be an effective and controllable approach to modify the properties of black phosphorus (BP), and improve the air-stability of BP and its nanoelectronic applications [Nat. Chem., 2016, 8, 597]. However, covalent functionalization of BP and related properties are poorly understood. Here we present a theoretical investigation on the electronic structure and transport property of chemically modified BP. Our calculations reveal that the molecule modification generates a rather flat energy band within the bandgap, which leads to a reduced hole mobility of BP. Alternatively, we propose to use polymers bonded to BP surface, aiming at a balance between functionality and carrier mobility. The polymer–BP composites preserve both electron and hole mobility of pristine BP. Meanwhile, the stability of polymer–BP composites in ambient condition is enhanced as well.
Co-reporter:Xiaojing Yao, Jinlan Wang, Gang Wu, Jianwei Xu, and Shuo-Wang Yang
The Journal of Physical Chemistry C 2016 Volume 120(Issue 44) pp:25612-25619
Publication Date(Web):October 13, 2016
DOI:10.1021/acs.jpcc.6b08389
Based on density functional theory calculations, we have studied the self-assembled growth of thiophene substituted alkenes, [H2C═CH-(CH2)n-thiophene] on hydrogen-terminated H-Si(100)2×1 and H-Ge(100)2×1 surfaces into aligned one-dimensional (1D) molecular arrays which are chemically bonded to the surfaces via the alkane chain. The thiophene rings at the top end of the molecular arrays are situated side by side and can undergo an in situ polymerization reaction into polythiophene once radicals are introduced to the thiophene rings, thereby forming polyalkylthiophene-Si/Ge(100)2×1 surface-grafted polymers. Like most of conductive polymers, these surface single polymer chains exhibit semiconducting character and can be made conductive either by p-doping or by applying an external electric field. More importantly, both surface-grafted polymers and substrates retain their electrical properties, and the polythiophene chains are the sole conductive channels in the structures. Our findings put forth a new way to fabricate conductive polymeric molecular wires on traditional semiconducting substrates, and could find potential application in nanoelectronic devices.
Co-reporter:Heng-Yun Ye; QiongHua Zhou; XiangHong Niu; Wei-Qiang Liao; Da-Wei Fu; Yi Zhang; Yu-Meng You; Jinlan Wang; Zhong-Ning Chen;Ren-Gen Xiong
Journal of the American Chemical Society 2015 Volume 137(Issue 40) pp:13148-13154
Publication Date(Web):September 18, 2015
DOI:10.1021/jacs.5b08290
Coupling of ferroelectricity and optical properties has become an interesting aspect of material research. The switchable spontaneous polarization in ferroelectrics provides an alternative way to manipulate the light–matter interaction. The recent observation of strong photoluminescence emission in ferroelectric hybrid organic–inorganic compounds, (pyrrolidinium)MnX3 (X = Cl or Br), is an attractive approach to high efficiency luminescence with the advantages of ferroelectricity. However, (pyrrolidinium)MnX3 only displays ferroelectricity near or below room temperature, which limits its future applications in optoelectronics and multifunctional devices. Here, we rationally designed and synthesized high-temperature luminescent ferroelectric materials. The new hybrid compound (3-pyrrolinium)MnCl3 has a very high Curie temperature, Tc = 376 K, large spontaneous electronic polarization of 6.2 μC/cm2, and high fatigue resistance, as well as high emission efficiency of 28%. This finding is a further step to the practical use of ferroelectric luminescence based on organic–inorganic compounds.
Co-reporter:Huabing Shu, Yunhai Li, Shudong Wang and Jinlan Wang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 6) pp:4542-4550
Publication Date(Web):07 Jan 2015
DOI:10.1039/C4CP05146G
Using density functional theory, the G0W0 method and Bethe–Salpeter equation calculations, we systematically explore the structural, electronic and optical properties of hydrogenated and fluorinated germanene. The hydrogenated/fluorinated germanene tends to form chair and zigzag-line configurations and its electronic and optical properties show close geometry dependence. The chair hydrogenated/fluorinated and zigzag-line fluorinated germanene are direct band-gap semiconductors, while the zigzag-line hydrogenated germanene owns an indirect band-gap. Moreover, the quasi-particle corrections are significant and strong excitonic effects with large exciton binding energies are observed. Moreover, the zigzag-line hydrogenated/fluorinated germanene shows highly anisotropic optical responses, which may be used as a good optical linear polarizer.
Co-reporter:Huabing Shu
The Journal of Physical Chemistry C 2015 Volume 119(Issue 27) pp:15526-15531
Publication Date(Web):June 10, 2015
DOI:10.1021/acs.jpcc.5b03679
Few-layer germanane has been successfully fabricated experimentally very recently and shown great potential applications in electronic and optoelectronic devices. In this work, we investigate thickness-dependent electronic and optical properties of Bernal-stacked few-layer germanane within the framework of many-body perturbation theory. Few-layer and bulk germanane are all direct band gap semiconductors, and the band gaps are tunable in a broad range. Strong excitonic effects are observed in few-layer germanane, leading to a distinct red shift in optical absorption spectra, and the exciton binding energy in monolayer germanane can be as large as 750 meV, which is 15 times larger than that of bulk germanane. More importantly, the quasi-particle band gaps, optical gaps, and exciton binding energies rapidly decrease with the increase of the layer and follow a power law of A + B/Nβ (0 < β < 2) with the stacking layer.
Co-reporter:Yunhai Li
The Journal of Physical Chemistry C 2015 Volume 119(Issue 44) pp:24950-24957
Publication Date(Web):October 15, 2015
DOI:10.1021/acs.jpcc.5b05935
Co-reporter:Yinghe Zhao; Qisheng Wu; Qian Chen
The Journal of Physical Chemistry Letters 2015 Volume 6(Issue 22) pp:4518-4524
Publication Date(Web):November 2, 2015
DOI:10.1021/acs.jpclett.5b02147
van der Waals (vdW) epitaxy of ultrathin organic films on two-dimensional (2D) atomic crystals has become a sovereign area because of their unique advantages in organic electronic devices. However, the dynamic mechanism of the self-assembly remains elusive. Here, we visualize the nanoscale self-assembly of organic molecules on graphene and boron nitride monolayer from a disordered state to a 2D lattice via molecular dynamics simulation for the first time. It is revealed that the assembly toward 2D ordered structures is essentially the minimization of the molecule–molecule interaction, that is, the vdW interaction in nonpolar systems and the vdW and Coulomb interactions in polar systems that are the decisive factors for the formation of the 2D ordering. The role of the substrate is mainly governing the array orientation of the adsorbates. The mechanisms unveiled here are generally applicable to a broad class of organic thin films via vdW epitaxy.
Co-reporter:Liang Ma; Xiao Cheng Zeng
The Journal of Physical Chemistry Letters 2015 Volume 6(Issue 20) pp:4099-4105
Publication Date(Web):September 25, 2015
DOI:10.1021/acs.jpclett.5b01841
Oxygen intercalation has been proven to be an efficient experimental approach to decouple chemical vapor deposition grown graphene from metal substrate with mild damage, thereby enabling graphene transfer. However, the mechanism of oxygen intercalation and associated rate-limiting step are still unclear on the molecular level. Here, by using density functional theory, we evaluate the thermodynamics stability of graphene edge on transition metal surface in the context of oxygen and explore various reaction pathways and energy barriers, from which we can identify the key steps as well as the roles of metal passivated graphene edges during the oxygen intercalation. Our calculations suggest that in well-controlled experimental conditions, oxygen atoms can be easily intercalated through either zigzag or armchair graphene edges on metal surface, whereas the unwanted graphene oxidation etching can be suppressed. Oxygen intercalation is, thus, an efficient and low-damage way to decouple graphene from a metal substrate while it allows reusing metal substrate for graphene growth.
Co-reporter:Yunhai Li
The Journal of Physical Chemistry C 2015 Volume 119(Issue 9) pp:4983-4989
Publication Date(Web):January 15, 2015
DOI:10.1021/jp506969r
The electronic structure and optical properties of hexagonal armchair and zigzag-edged graphene quantum dots (GQDs) are investigated within the framework of many-body perturbation theory. Many-body effects are significant due to quantum confinement and reduced screening. The quasi-particle corrections and exciton binding energies can be several eV, much larger than those of other carbon allotropes with higher dimensionality. All the GQDs show similar absorption spectra when electron–hole interaction is included, with a prominent peak emerging below the absorption onset of the noninteracting spectrum. This peak is contributed by a pair of double-degenerate excited states originating from the transitions between degenerate frontier orbitals. The spin singlet–triplet splitting is closely related to the electron–hole overlap, which can be approximately measured by the overlap between frontier orbitals involved in the optical transitions. The strong many-body effects in GQDs should be of great importance in optoelectronic applications.
Co-reporter:Zilu Wang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 9) pp:4752-4758
Publication Date(Web):January 29, 2015
DOI:10.1021/jp507751p
Vertically stacked two-dimensional multilayer structures have become a promising prototype for functionalized nanodevices due to their wide range of tunable properties. In this paper we performed first-principles calculations to study the electronic structure of nontwisted and twisted bilayers of hybrid graphene/MoS2 (Gr/MoS2) and MoS2/MoS2. Both twisted bilayers of Gr/MoS2 and MoS2/MoS2 show significant differences in band structures from the nontwisted ones with the appearance of the crossover between direct and indirect band gap and gap variation. More interestingly, the band structures of twisted Gr/MoS2 with different rotation angles are very different from each other, while those of MoS2/MoS2 are very similar. The variation of band structure with rotation angle in Gr/MoS2 is, indeed, originated from the misorientation-induced lattice strain and the sensitive band-strain dependence of MoS2.
Co-reporter:Jing Pan, Zilu Wang, Qian Chen, Jingguo Hu and Jinlan Wang
Nanoscale 2014 vol. 6(Issue 22) pp:13565-13571
Publication Date(Web):10 Sep 2014
DOI:10.1039/C4NR02829E
To achieve photoelectrochemical (PEC) activity of MoS2 for hydrogen production through water splitting, the band edges of MoS2 should match with the hydrogen and oxygen production levels. Our first-principles calculations show that the band edges of monolayer MoS2 can be effectively tuned by surface ligand functionalization, resulting from the intrinsic dipole of the ligand itself and the induced dipole at the ligand/MoS2 interface. We further explore the influence of ligand coverage, ligand functionalization and the substrate on the band structure of MoS2. The hybrid C6H5CH2NH2/MoS2/graphene structures may be compelling candidates as they satisfy the stringent requirements of PEC water splitting.
Co-reporter:Qian Chen, Yixin Ouyang, Shijun Yuan, Runze Li, and Jinlan Wang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 19) pp:16835
Publication Date(Web):September 4, 2014
DOI:10.1021/am504216k
Synthesis of two-dimensional (2D) metal chalcogenide based half-metallic nanosheets is in high demand for modern electronics and spintronics applications. Herein, we predict from first-principles calculations that the 2D heterostructure Co/MoS2, consisting of a monolayer of Co atoms deposited on a single MoS2 sheet, possesses robust ferromagnetic and half-metallic features and exhibits 100% spin-filter efficiency within a broad bias range. Its ferromagnetic and half-metallic nature persists even when overlaid with a graphene sheet. Because of the relatively strong surface binding energy and low clustering ratio of Co atoms on the MoS2 surface, we predict that the heterostructure is synthesizable via wetting deposition of Co on MoS2 by electron-beam evaporation technique. Our work strongly suggests Co/MoS2 as a compelling and feasible candidate for highly effective information and high-density memory devices.Keywords: and density functional theory; metal chalcogenide; spintronics; surface
Co-reporter:Yuming Chen, Lijuan Meng, Weiwei Zhao, Zheng Liang, Xing Wu, Haiyan Nan, Zhangting Wu, Shan Huang, Litao Sun, Jinlan Wang and Zhenhua Ni
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 39) pp:21682-21687
Publication Date(Web):26 Aug 2014
DOI:10.1039/C4CP03386H
Bilayer graphene as a prototype of two-dimensional stacked material has recently attracted great attention. The twist angle between graphene layers adds another dimension to control its properties. In this study, we used Raman mapping to investigate the twist angle dependence of properties of twisted bilayer graphene (TBG) with irregular grains that was fabricated by chemical vapor deposition (CVD). Different Raman parameters including intensity, width, and position of G and 2D peaks were used to distinguish TBG with different twist angles. The statistical results from Raman imaging on the distribution of twist angle are consistent with the results from selected area election diffraction (SAED). Finally, the Raman peak at approximately 1347 cm−1 for TBG with a large twist angle was assigned to the D-like peak, although it has similar excitation energy dependence of frequency as the defect-induced D peak. Theoretical calculation further confirmed that vacancy-like defect is not favored in the formation energy for TBG with a large twist angle as compared to monolayer graphene or TBG with other twist angles. These results will help to advance the understanding of TBG properties, especially for CVD samples with irregular grains.
Co-reporter:Jing Pan;Dr. Shudong Wang;Dr. Qian Chen; Jingguo Hu; Jinlan Wang
ChemPhysChem 2014 Volume 15( Issue 8) pp:1611-1618
Publication Date(Web):
DOI:10.1002/cphc.201301059
Abstract
To look for efficient visible light-driven catalysts for photo-electrochemical (PEC) water-splitting, the band structure and optical absorption of monodoped, compensated, and noncompensated n–p pairs of co-doped bulk ZnO are systemically studied by using both general gradient approximation and hybrid density functional theory approaches (PBE and HSE). Calculations show that n–p co-doping cannot only enhance the stability that stems from the strong electrostatic attraction between the n- and p-type dopants, but also effectively reduce the band-gap of ZnO. More importantly, compensated (Ti+C) and noncompensated (Sc+C) and (Cr+C) co-doped ZnO may be compelling candidates for PEC water-splitting because of their narrowed band-gaps, potentially reduced electron–hole recombination centers, appropriate band-edge positions, enhanced optical absorption, and good stability.
Co-reporter:Liang Ma, Jinlan Wang, Joanne Yip, and Feng Ding
The Journal of Physical Chemistry Letters 2014 Volume 5(Issue 7) pp:1192-1197
Publication Date(Web):March 18, 2014
DOI:10.1021/jz500254u
Catalytic cutting by transition-metal (TM) particles is a promising method for the synthesizing of high-quality graphene quantum dots and nanoribbons with smooth edges. Experimentally, it is observed that the cutting always results in channels with zigzag (ZZ) or armchair (AC) edges. However, the driving force that is responsible for such a cutting behavior remains a puzzle. Here, by calculating the interfacial formation energies of the TM-graphene edges with ab initio method, we show that the surface of a catalyst particle tends to be aligned along either AC or ZZ direction of the graphene lattice, and thus the cutting of graphene is guided as such. The different cutting behaviors of various catalysts are well-explained based on the competition between TM-passivated graphene edges and the etching-agent-terminated ones. Furthermore, the kinetics of graphene catalytic cutting along ZZ and AC directions, respectively, are explored at the atomic level.Keywords: ab initio calculations; cutting; graphene; heterogeneous catalysis; nanostructures;
Co-reporter:Haiyan Nan, Zilu Wang, Wenhui Wang, Zheng Liang, Yan Lu, Qian Chen, Daowei He, Pingheng Tan, Feng Miao, Xinran Wang, Jinlan Wang, and Zhenhua Ni
ACS Nano 2014 Volume 8(Issue 6) pp:5738
Publication Date(Web):May 16, 2014
DOI:10.1021/nn500532f
We report on a strong photoluminescence (PL) enhancement of monolayer MoS2 through defect engineering and oxygen bonding. Micro-PL and Raman images clearly reveal that the PL enhancement occurs at cracks/defects formed during high-temperature annealing. The PL enhancement at crack/defect sites could be as high as thousands of times after considering the laser spot size. The main reasons of such huge PL enhancement include the following: (1) the oxygen chemical adsorption induced heavy p doping and the conversion from trion to exciton; (2) the suppression of nonradiative recombination of excitons at defect sites, which was verified by low-temperature PL measurements. First-principle calculations reveal a strong binding energy of ∼2.395 eV for an oxygen molecule adsorbed on a S vacancy of MoS2. The chemically adsorbed oxygen also provides a much more effective charge transfer (0.997 electrons per O2) compared to physically adsorbed oxygen on an ideal MoS2 surface. We also demonstrate that the defect engineering and oxygen bonding could be easily realized by mild oxygen plasma irradiation. X-ray photoelectron spectroscopy further confirms the formation of Mo–O bonding. Our results provide a new route for modulating the optical properties of two-dimensional semiconductors. The strong and stable PL from defects sites of MoS2 may have promising applications in optoelectronic devices.Keywords: defect engineering; excitons; MoS2; oxygen bonding; photoluminescence; plasma
Co-reporter:Lijuan Meng, Jian Jiang, Jinlan Wang, and Feng Ding
The Journal of Physical Chemistry C 2014 Volume 118(Issue 1) pp:720-724
Publication Date(Web):December 6, 2013
DOI:10.1021/jp409471a
Structural defects are almost unavoidable in graphene synthesis and they may significantly deteriorate the performance of graphene in applications. Although defects of small sizes may be easily healed by the rearrangement of a few C atoms near the defect site, the healing of large ones is rather complicated and the healing mechanism remains unclear. In this work, we reveal a catalytic healing of large structural defects in graphene based on both classical molecular dynamics simulations and density functional theory calculations. The kinetic healing processes of large vacancy holes in graphene with and without a nickel catalyst are explored. Our results show that the presence of a single Ni atom can (1) catalyze the dissociation of carbon feedstock, (2) heal nonhexagonal C rings formed during the addition of C atoms, and (3) prevent the formation of hanging C chains and arching C patches, and ultimately lead to the successful healing of large structural defects in graphene.
Co-reporter:Qian Chen and Jinlan Wang
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 41) pp:17793-17797
Publication Date(Web):02 Sep 2013
DOI:10.1039/C3CP52391H
Room-temperature ferromagnetism (RTFM) has been achieved in rare earth (RE) element doped ZnO nanostructures, while the mechanism of RTFM is still under debate. In this work, we investigated the electronic structure and magnetic properties of Nd-doped ZnO nanowires, and the influence of oxygen vacancies by using ab initio calculations. The impurity Nd atoms prefer to substitute the surface Zn sites and be ferromagnetically coupled with a moment of ∼3.0 μB per Nd in the doped ZnO nanowires, through a superexchange interaction mediated by the oxygen ions. More interestingly, the surface oxygen vacancy can greatly enhance the stability of the ferromagnetic state via the “local carriers” of Nd- and Zn-s electrons, which accounts for the room-temperature ferromagnetism in the Nd-doped ZnO nanowires. This mechanism and analysis can be applied to other rare earth element doped semiconductor nanostructures.
Co-reporter:Yanbiao Wang, Qionghua Zhou, Mingli Yang, Jinlan Wang
Computational and Theoretical Chemistry 2013 Volume 1021() pp:262-267
Publication Date(Web):1 October 2013
DOI:10.1016/j.comptc.2013.07.043
•Single atom catalysis of isomorphous substituted bimetallic oxide TMV3O10 (TM = Sc, Ti, Cr and Co) was explored.•The adsorption of CO is greatly affected by the TM substituent in the clusters.•TMV3O10 exhibit specific and tunable single atom catalytic activity.•The d-projected DOS near the EF plays an important role in the catalytic performance of single atom catalyst.Single-atom catalysis of isomorphous substituted bimetallic oxide TMV3O10 (TM = Sc, Ti, Cr and Co) is explored by spin–polarized density functional theory calculations. The single atom substitution in V4O10 does not make significant change to the geometric or electronic structures of the cluster; while it brings specific and tunable catalytic activity depending on the TM substituent. The d-projected density of state near the Fermi level is found to play important roles in the catalytic performance of single-atom catalysts. Our findings reveal the structural basis of the activity of bimetallic oxide clusters and shed some lights on the catalytic mechanism of single-atom catalysis.Graphical abstractCO oxidation reaction via single-atom catalyst of TMV3O10.
Co-reporter:Liang Ma; Jinlan Wang;Dr. Feng Ding
ChemPhysChem 2013 Volume 14( Issue 1) pp:47-54
Publication Date(Web):
DOI:10.1002/cphc.201200253
Abstract
Graphene, the thinnest two-dimensional material in nature, has abundant distinctive properties, such as ultrahigh carrier mobility, superior thermal conductivity, very high surface-to-volume ratio, anomalous quantum Hall effect, and so on. Laterally confined, thin, and long strips of graphene, namely, graphene nanoribbons (GNRs), can open the bandgap in the semimetal and give it the potential to replace silicon in future electronics. Great efforts are devoted to achieving high-quality GNRs with narrow widths and smooth edges. This minireview reports the latest progress in experimental and theoretical studies on GNR synthesis. Different methods of GNR synthesis—unzipping of carbon nanotubes (CNTs), cutting of graphene, and the direct synthesis of GNRs—are discussed, and their advantages and disadvantages are compared in detail. Current challenges and the prospects in this rapidly developing field are also addressed.
Co-reporter:Dr. Tingting Zhang;Dr. Liyan Zhu;Dr. Shijun Yuan ; Dr. Jinlan Wang
ChemPhysChem 2013 Volume 14( Issue 15) pp:3483-3488
Publication Date(Web):
DOI:10.1002/cphc.201300563
Abstract
We systematically investigate the interactions and magnetic properties of a series of 3d transition-metal (TM; Sc–Ni) atoms adsorbed on perfect graphene (G6), and on defective graphene with a single pentagon (G5), a single heptagon (G7), or a pentagon–heptagon pair (G57) by means of spin-polarized density functional calculations. The TM atoms tend to adsorb at hollow sites of the perfect and defective graphene, except for G6Cr, G5Cr, and G5Ni. The binding energies of TMs on defective graphene are remarkably enhanced and show a V-shape, with GNCr and GNMn having the lowest binding energies. Furthermore, complicated element- and defect-dependent magnetic behavior is observed in GNTM. Particularly, the magnetic moments of GNTM linearly increase by about 1 μB and follow a hierarchy of G7TM<G57TM<G5TM as the TM varies from Sc to Mn, and the magnetic moments begin to decrease afterward; by choosing different types of defects, the magnetic moments can be tuned over a broad range, for example, from 3 to 6 μB for GNCr. The intriguing element- and defect-dependent magnetic behavior is further understood from electron- and back-donation mechanisms.
Co-reporter:Dr. Tingting Zhang;Dr. Liyan Zhu;Dr. Shijun Yuan ; Dr. Jinlan Wang
ChemPhysChem 2013 Volume 14( Issue 15) pp:
Publication Date(Web):
DOI:10.1002/cphc.201390072
Co-reporter:Yanbiao Wang, Guangfen Wu, Mingli Yang, and Jinlan Wang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 17) pp:8767-8773
Publication Date(Web):April 5, 2013
DOI:10.1021/jp3122775
The competition between the Eley–Rideal (ER) and the Langmuir–Hinshelwood mechanisms of CO oxidation on Cun and CunO (n = 6, 7) clusters was explored by means of spin-polarized density functional theory calculations. The separate and successive adsorptions of CO and O2 on the clusters were studied. CO and O2 molecules exhibit different adsorption behaviors, and a cooperative effect was noted for their coadsorption. The reaction pathways of CO oxidization were then investigated by locating the transition-state and intermediate structures. The ER mechanism was more favorable for the reactions on Cu6,7 and Cu6O but was less favorable on Cu7O. The ER or LH preference of the CO + O2 reaction on the clusters was further rationalized. We found that activation of O2 is the key issue that affects the ER–LH competition. The pathway, either ER or LH, in which O2 is highly activated is always preferred, while the O2 activation depends on its adsorption pattern, site, and sequence in the presence of CO.
Co-reporter:Shijun Yuan, Lijuan Meng, and Jinlan Wang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 28) pp:14796-14803
Publication Date(Web):June 24, 2013
DOI:10.1021/jp400944c
Synthesizing large-area high-quality graphene at low temperature is crucial for graphene applications in electronics and spintronics. In this work, we demonstrate that adsorption of a single active metal atom into inactive matrix would remarkably improve the catalytic reactivity. Our first-principles calculations show that the reaction barrier of methane dehydrogenation is remarkably reduced from 1.76 eV on flat Cu (100) surface to 1.00 eV on a Ni atom adsorbed Cu (100) surface. Moreover, the adsorbed Ni atom is found to serve as the active reaction center, which might provide a possibility of manipulating the graphene nucleation position for controllable chemical vapor deposition growth. Additionally, different dehydrogenation behaviors are detected and well understood in terms of electronic structures involved in the reactions. This study shows the potential of synthesizing high-quality graphene at relatively low temperatures with the assistance of Ni adsorption on Cu foils, and it can be extended to other metal and substrates.
Co-reporter:Lijuan Meng, Zilu Wang, Jian Jiang, Yonghong Yang, and Jinlan Wang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 29) pp:15260-15265
Publication Date(Web):July 3, 2013
DOI:10.1021/jp312802e
The evolution of carbon structures and the kinetics of graphene nucleation on nickel step surfaces are investigated by classical molecular dynamics simulations and density functional theory calculations. It is found that the evolution mechanism of C structures on the step surface is the same as that on the flat terrace when no substrate Ni atom is pulled out of the surface. But the defects involved with the pulled-out Ni atoms can be efficiently healed with the assistance of the step atoms on the step surface, while they are rather difficult to be healed on the terrace. Compared with the terrace, the step significantly lowers the healing barrier of the defect involved with the pulled-out Ni atom and therefore results in a very fast healing of the defect. These results demonstrate that the presence of the step is beneficial to synthesize better graphene for chemical vapor deposition growth on Ni substrate.
Co-reporter:Dandan Wang, Qian Chen, Guozhong Xing, Jiabao Yi, Saidur Rahman Bakaul, Jun Ding, Jinlan Wang, and Tom Wu
Nano Letters 2012 Volume 12(Issue 8) pp:3994-4000
Publication Date(Web):June 25, 2012
DOI:10.1021/nl301226k
As an important class of spintronic material, ferromagnetic oxide semiconductors are characterized with both charge and spin degrees of freedom, but they often show weak magnetism and small coercivity, which limit their applications. In this work, we synthesized Nd-doped ZnO nanowire arrays which exhibit stable room temperature ferromagnetism with a large saturation magnetic moment of 4.1 μB/Nd as well as a high coercivity of 780 Oe, indicating giant magnetic anisotropy. First-principles calculations reveal that the remarkable magnetic properties in Nd-doped ZnO nanowires can be ascribed to the intricate interplay between the spin moments and the Nd-derived orbital moments. Our complementary experimental and theoretical results suggest that these magnetic oxide nanowires obtained by the bottom-up synthesis are promising as nanoscale building blocks in spintronic devices.
Co-reporter:Yanbiao Wang, Guangfen Wu, Jinli Du, Mingli Yang, and Jinlan Wang
The Journal of Physical Chemistry A 2012 Volume 116(Issue 1) pp:93-97
Publication Date(Web):December 6, 2011
DOI:10.1021/jp208314g
Using a cluster model, we investigated the similarities and differences in chemical activity and the magnetic properties of Scn clusters (n = 2–13) and their oxides, ScnO, toward CO molecule adsorption via a spin-polarized density functional theory approach. The Scn and ScnO clusters have similar chemical activity at small sizes of n = 2–10, whereas remarkable differences are observed at large sizes of n = 11–13. More interestingly, different magnetic responses are found in the Scn and ScnO clusters with the presence of CO molecule: The magnetic moment is attenuated significantly for Scn with n = 2, 4, 12, and 13, whereas for ScnO, it is enhanced at n = 4 and 13 and is reduced for n = 7, 8, 10, and 11. In particular, the magnetic moment remarkably increases from 7 μB of Sc13O to 13 μB of Sc13OCO, whereas it reduces from 19 μB of Sc13 to 5 μB of Sc13CO.
Co-reporter:Shudong Wang
The Journal of Physical Chemistry C 2012 Volume 116(Issue 18) pp:10193-10197
Publication Date(Web):April 19, 2012
DOI:10.1021/jp2125872
The electronic structure and optical properties of very recently synthesized chevron-type graphene nanoribbon (CGNR) are investigated within many-body Green’s function and Bethe–Salpeter equation formalism. The CGNR can effectively confine both electrons and holes, leading to its exciton binding energy larger than that of regular GNRs. The excitonic peaks owing to electron–hole interactions dominate the optical spectra with a significant blue-shift and a different line shape in CGNR compared with those in regular GNRs. Moreover, the singlet–triplet exciton splitting of CGNR is also larger than that of the regular GNRs, which is expected to show high fluorescence luminescence efficiency. The enhanced excitonic effects in CGNR should be of great importance in optoelectronic applications.
Co-reporter:Liang Ma; Jinlan Wang;Dr. Feng Ding
Angewandte Chemie 2012 Volume 124( Issue 5) pp:1187-1190
Publication Date(Web):
DOI:10.1002/ange.201105920
Co-reporter:Liang Ma; Jinlan Wang;Dr. Feng Ding
Angewandte Chemie International Edition 2012 Volume 51( Issue 5) pp:1161-1164
Publication Date(Web):
DOI:10.1002/anie.201105920
Co-reporter:Xiuyun Zhang, Jiu Han, Yongjun Liu, and Jinlan Wang
The Journal of Physical Chemistry C 2012 Volume 116(Issue 9) pp:5414-5419
Publication Date(Web):February 6, 2012
DOI:10.1021/jp211419a
We systematically investigate the structural, electronic, and magnetic properties of one-dimensional bimetallic naphethalene sandwich nanowires, [Np2V2TM2]∞ (TM = Ti, Cr, Mn, Fe, Np = C10H8, naphethalene) by employing ab initio calculations. Three structures with different alignments of TM atoms (isomer-I, -II, -III) are considered, and they are all of high stability with exceptions of [Np2V2Mn2]∞ (isomer-II, -III) and [Np2V2Fe2]∞ (isomer-III). Furthermore, the electronic and magnetic properties of [Np2V2TM2]∞ show clear dependence on chemical component and geometries. Most sandwich wires favor ferromagnetic coupling, while [Np2V2Ti2]∞ (isomer-I, -III) shows antiferromagnetic ground states. Interestingly, [Np2V2Cr2]∞ (isomer-II, -III), [Np2V2Mn2]∞ (isomer-I), and [Np2V2Fe2]∞ (isomer-I) are found to be robust ferromagnetic half-metals, and [Np2V2Cr2]∞ (isomer-I) is a ferromagnetic quasi-half metal.
Co-reporter:Lijuan Meng, Qing Sun, Jinlan Wang, and Feng Ding
The Journal of Physical Chemistry C 2012 Volume 116(Issue 10) pp:6097-6102
Publication Date(Web):February 15, 2012
DOI:10.1021/jp212149c
Grasping the fundamentals of graphene growth is vital for graphene synthesis. By employing classical molecular dynamics with the ReaxFF potential, we have investigated the evolution of carbon structures and the growth kinetics of graphene on Ni(111) surface at different temperatures. Our results showed that low C concentration leads to the dissolution of C atoms into Ni only, whereas high C concentration leads to the formation of graphene island. By efficient defect annealing at the optimal temperature of ∼1000 K, the quality of graphene island can be significantly improved. Furthermore, a graphene island can grow larger by capturing the deposited C atoms and form more hexagons on the edge with its self-healing capability during the growth. These underlying observations and understandings are instructive for the control of the CVD growth of graphene.
Co-reporter:Liyan Zhu, Jinlan Wang, and Feng Ding
The Journal of Physical Chemistry C 2012 Volume 116(Issue 14) pp:8027-8033
Publication Date(Web):March 19, 2012
DOI:10.1021/jp210058c
In real device application, the sealing of graphene as that in the silicon microelectronic industry is required to ensure a stable local environment. In this work, through first-principles calculations, we demonstrate that single-atomic-thick graphene and graphene nanoribbons (GNRs) sealed between diamond layers maintain their intrinsic electronic properties. Furthermore, the study shows that the doping type and level and the conductivity of sealed graphene and GNRs can be tuned through the external pressure or the selection of the sealing material. This opens a door of using sealed graphene/GNR to replace the recently used freestanding or supported ones for robust electronic/spintronic device synthesis.
Co-reporter: Jinlan Wang;Liang Ma;Dr. Qinghong Yuan;Liyan Zhu;Dr. Feng Ding
Angewandte Chemie International Edition 2011 Volume 50( Issue 35) pp:
Publication Date(Web):
DOI:10.1002/anie.201104525
Co-reporter:Jinli Du, Mingli Yang, and Jinlan Wang
The Journal of Physical Chemistry A 2011 Volume 115(Issue 37) pp:10259-10265
Publication Date(Web):August 15, 2011
DOI:10.1021/jp206108u
We have studied C2H4 and O2 molecules separately or simultaneously for adsorption on Vn (n = 2–8) clusters, and Vn clusters catalyzed ethylene oxidation to acetaldehyde using spin-polarized density functional theory calculations. Molecular adsorption and clear size-dependent adsorption energy are predicted for C2H4. O2 is dissociately adsorbed with nearly constant adsorption energy. In the case of coadsorption, O2 and C2H4 adsorb on the Vn surface simultaneously. Each keeps the same adsorption form, molecular or dissociative, as in separate adsorption. The noted cooperative effect is noted in C2H4 and O2 coadsorption, which activates the C–C double bond of C2H4 and favors its oxidization. Furthermore, both the separate and coadsorptions result in magnetic enhancement or reduction of Vn, which is found to be dependent on the cluster size and the adsorbates. In addition, we reveal the reaction mechanism of V2 (V6)-catalyzed ethylene oxidation to acetaldehyde and find the overall reaction is exothermic and barrierless.
Co-reporter: Jinlan Wang;Liang Ma;Dr. Qinghong Yuan;Liyan Zhu;Dr. Feng Ding
Angewandte Chemie International Edition 2011 Volume 50( Issue 35) pp:8041-8045
Publication Date(Web):
DOI:10.1002/anie.201101022
Co-reporter: Jinlan Wang;Liang Ma;Dr. Qinghong Yuan;Liyan Zhu;Dr. Feng Ding
Angewandte Chemie 2011 Volume 123( Issue 35) pp:8191-8195
Publication Date(Web):
DOI:10.1002/ange.201101022
Co-reporter: Jinlan Wang;Liang Ma;Dr. Qinghong Yuan;Liyan Zhu;Dr. Feng Ding
Angewandte Chemie 2011 Volume 123( Issue 35) pp:
Publication Date(Web):
DOI:10.1002/ange.201104525
Co-reporter:Xiuyun Zhang ; Zhi Tian ; Shuo-Wang Yang
The Journal of Physical Chemistry C 2011 Volume 115(Issue 7) pp:2948-2953
Publication Date(Web):February 2, 2011
DOI:10.1021/jp109253a
We systematically investigate the stability and electronic and magnetic properties of one-dimensional (1D) bimetallic organic sandwich molecular wires (BOSMWs), [CpTiCpTM]∞ (TM = Sc−Co, Cp = C5H5), [CpCrCpTM]∞ (TM = V, Mn, Co), and [CpFeCpTM]∞ (TM = Cr, Co), using ab initio methods. All the BOSMWs are highly stable due to mixed ionic−covalent bonding. With the exceptions of [CpTiCpV]∞, [CpTiCpMn]∞, and [CpCrCpV]∞ exhibiting antiferromagnetic behavior, all the other BOSMWs are ferromagnetic with tunable magnetic moments. In particular, magnetic moments of [CpTiCpCo]∞ and [CpCrCpMn]∞ can be as high as 5 μB per unit cell. Our calculations further show that [CpTiCpTM]∞ (TM = Cr, Fe), [CpCrCpTM]∞ (TM = Fe, Co), and [CpFeCpCo]∞ are robust half-metals (HMs) with large HM gaps. Most importantly, we identify an empirical valence electron filling rule for these BOSMWs, and a BOSMW is found to be a half-metallic ferromagnet whenever N − 5(10) = 5(7) (N is the sum of the valence electrons of two metal atoms). This electron filling rule, together with the HM equations formulized in this study, can be extended to predict new HM BOSMWs.
Co-reporter:Liang Ma ; Hong Hu ; Liyan Zhu
The Journal of Physical Chemistry C 2011 Volume 115(Issue 14) pp:6195-6199
Publication Date(Web):March 23, 2011
DOI:10.1021/jp110649m
The electronic and magnetic properties of quasi-1D zigzag triwing graphene (ZZ-TWG) ribbons with boron and nitrogen (BN) doping were investigated by means of a spin-polarized density functional theory approach. Our results showed that asymmetric BN doping can give rise to half-metallicity and suppress spin polarization of the doped wings, making the BN-doped ZZ-TWGs potential application in spintronics devices. Heavily doping can turn metallic ZZ-TWG ribbons into semiconductors. A critical ratio of BN to C and appropriate doping site (e.g., ribbon’s edges) are required for achieving specific electronic properties. An effective path of engineering electronic properties of ZZ-TWGs by BN doping was suggested.
Co-reporter:Tingting Zhang ; Liyan Zhu ; Zhi Tian
The Journal of Physical Chemistry C 2011 Volume 115(Issue 30) pp:14542-14547
Publication Date(Web):June 28, 2011
DOI:10.1021/jp202531c
Structural, electronic, and magnetic properties of transition metal (TM)–bis(dicarbollide) (TM(Dcb)2; TM = Sc–Mn, Dcb = dicarbollide) sandwich clusters and their charged counterparts (TM(Dcb)2+, TM(Dcb)2–) are systematically investigated by using all electron density functional theory approach. All TM(Dcb)2 sandwich clusters are highly stable because of the formation of ionic–covalent bonding. The Ti(Dcb)2 is the most stable, the Sc- and V(Dcb)2 are intermediate, and the Cr- and Mn(Dcb)2 are the least stable. The magnetic moment of TM(Dcb)2 exhibits a clear element-dependent variation with 1 μB for Sc(Dcb)2 and 0 μB for Ti(Dcb)2 and with a linear increased trend by 1 μB from Ti(Dcb)2 to Mn(Dcb)2. This element-dependent magnetic behavior can be well understood by electron transfer as well as spin density distribution. We further reveal that charging can induce the rotation of the ligands in the Sc-, V-, Cr-, and Mn(Dcb)2 clusters, which makes them promising candidates for molecular motors.
Co-reporter:Liyan Zhu, Jinlan Wang, Tingting Zhang, Liang Ma, Chee Wah Lim, Feng Ding and Xiao Cheng Zeng
Nano Letters 2010 Volume 10(Issue 2) pp:494-498
Publication Date(Web):January 8, 2010
DOI:10.1021/nl903278w
Inspired by strong mechanical stability of “Y”-shaped beams for building construction, we design a new class of quasi-one-dimensional graphene nanostructures, namely, tri-wing graphene (TWG) nanoribbons. TWG possesses significantly augmented mechanical stability against torsional and compression forces, and also each wing of the TWG can retain independent electronic properties of the constituent graphene nanoribbons. As such, by tailoring the wing structures, the TWGs can provide broader property tunability for nanoelectronic application. In addition, zigzag-edged TWG is a metallic ferromagnet with a large magnetic moment. When its edges are decorated with suitable chemical functional groups, a TWG can be converted to a half metal for potential spintronic applications.
Co-reporter:Liyan Zhu, Tingting Zhang, Mengxi Yi and Jinlan Wang
The Journal of Physical Chemistry A 2010 Volume 114(Issue 34) pp:9398-9403
Publication Date(Web):August 2, 2010
DOI:10.1021/jp106129r
We have systematically investigated mixed inorganic/organic ligand sandwich clusters comprised of 3d transition metal (TM) atoms with C60 and benzene (Bz) molecules, BzTMC60, by using all electron density functional theory. We found the bonding type between TM and C60 in the ground state evolves from η6 (TM = Sc−Cr) to η5 (TM = Mn) and then to η2 (TM = Fe, Co) with increasing number of d electrons of TM. The BzTMC60 clusters (TM = Sc−Co) are of high stability through ionic−covalent interactions. The BzCrC60 cluster has the lowest binding energy due to its largest spin-flip energy and the weakest ionic bonding interaction between the CrBz unit and C60. With the exception of BzTiC60 being triplet, all the BzTMC60 clusters energetically prefer the lowest available spin states, e.g., the ground spin state is either a singlet (with an even number of electrons) or a doublet (with an odd number of electrons). Moreover, the magnetic properties of BzTMC60 show clear dependence to the bond type between TM and C60, and the η5-ligand configurations tend to be in high spin states.
Co-reporter:Jinli Du, Guangfen Wu, and Jinlan Wang
The Journal of Physical Chemistry A 2010 Volume 114(Issue 39) pp:10508-10514
Publication Date(Web):September 10, 2010
DOI:10.1021/jp106321s
Using spin-polarized density functional calculations, we have studied the interaction of carbon monoxide (CO) with bimetallic ConMn (n = 1−6) and ConMn6−n (n = 0−6) clusters. Various adsorption sites including atop, hollow, and bridge adsorption patterns and different possible spin states are considered. The CO molecule prefers to adsorb at the Co site rather than at the Mn site. Atop adsorption structure is energetically more favored over the hollow and bridge adsorption ones for the bimetallic clusters with an exception of Co5Mn. Large adsorption energy is found at Co3Mn, Co2Mn4, and Co3Mn3, associating with the relative stability of the bare Co−Mn clusters and the electrostatic interactions as well as adsorption patterns. The activation of the C−O bond and the red shift of the C−O stretching frequency are sensitive to the adsorption sites and high chemical activity is identified for Co6, Co5Mn, and Mn6 clusters. More interestingly, the adsorption of CO has different influence on the magnetism of the clusters: the magnetic moment remains unchanged for CoMn and Co2Mn, while it is reduced by 2 μB for ConMn (n = 3−6) and ConMn6−n (n = 0−5) and is enhanced by 2 μB for Mn6 when a CO molecule is loaded to the cluster.
Co-reporter:Yanbiao Wang, Mingli Yang, Jinlan Wang
Journal of Molecular Structure: THEOCHEM 2010 Volume 953(1–3) pp:55-60
Publication Date(Web):15 August 2010
DOI:10.1016/j.theochem.2010.05.002
Ab initio study on bimetallic oxide clusters (TiVOm, VMnOm and MnCoOm, m = 3, 4) is reported. These clusters adopt a four-membered ring structure and possess large binding energies, which decrease monotonously as composition varies from Ti to Co for both trioxide and tetroxide clusters. Enhanced magnetism is found for the bimetallic oxide clusters except MnCoO3, as compared to that of the monometallic counterparts. The tetroxide clusters have smaller magnetic moments than the corresponding trioxide, resulting from the charge transfer and the strong hybridization between the metal atom and the additional O atom.
Co-reporter:Guangfen Wu, Jinlan Wang, Xiao Cheng Zeng, Hong Hu and Feng Ding
The Journal of Physical Chemistry C 2010 Volume 114(Issue 27) pp:11753-11757
Publication Date(Web):June 17, 2010
DOI:10.1021/jp102005k
We systematically studied effects of selective hydrogenation of single-walled carbon nanotube (SWNT) on the shape of tube cross section based on a mechanical relaxation model and ab initio calculations. We found that fully hydrogenated SWNTs (FH-SWNTs) are energetically more favorable than partially hydrogenated ones. We uncovered a new channel for the strain relaxation at the nanoscale, in contrast to the known plasticity or buckling channel. We showed that the curvature strain energy of a cylindrical FH-SWNT can be significantly relieved by flipping a few rows of H atoms from outside to inside of the tube. We conclude that selective hydrogenation of SWNTs not only can be an effective way to achieve highly stable configurations of FH-SWNTs but also can be used to control the shape of tube cross section (triangle, square, etc.) for nanomechanic applications.
Structural, electronic, and magnetic properties of TMZn11O12 and TM2Zn10O12 clusters (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu)
Co-reporter:Qian Chen, Jinlan Wang
Chemical Physics Letters 2009 Volume 474(4–6) pp:336-341
Publication Date(Web):4 June 2009
DOI:10.1016/j.cplett.2009.05.006
We investigate the structural, electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) doped (ZnO)12 clusters (TMZn11O12 and TM2Zn10O12) by using density functional theory approach. All the substitutional doping clusters are of high stability and remain quasi-cage structures with the exception of Ti2Zn10O12 and V2Zn10O12. The doped TMZn11O12 clusters are magnetic except TM = Ti, whereas the TM2Zn10O12 clusters are either antiferromagnetic or paramagnetic, suggesting that concentration of TM dopant has great influence on the magnetism of the ZnO-based nanostructures. The magnetic behavior is understood from charge-transfer model and partial density of states.Structural, electronic and magnetic properties of singly and doubly transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) doped (ZnO)12 clusters are studied using density functional theory approach.
Co-reporter:Xiuyun Zhang, Jinlan Wang, Yi Gao and Xiao Cheng Zeng
ACS Nano 2009 Volume 3(Issue 3) pp:537
Publication Date(Web):March 3, 2009
DOI:10.1021/nn800794c
Structural and magnetic properties of multidecker sandwich clusters TMn(ferrocene)n+1 [TM = V, Ti, Sc, Mn, ferrocene=FeCp2, n = 1−3] and corresponding one-dimensional sandwich nanowires (n = ∞) are studied by means of gradient-corrected density functional theory. The TMn(FeCp2)n+1 clusters are highly stable polyferrocene-like sandwich structures due to strong Fe−Cp interaction. The total magnetic moment of TMn(FeCp2)n+1 (TM = V, Ti, Mn) increases linearly with the size n. More strikingly, Tin(FeCp2)n+1 and Vn(FeCp2)n+1 (n = 1−3) exhibit high magnetic moments 4, 8, 12 μB and 1, 6, 11 μB, respectively. In contrast, Scn(FeCp2)n+1 clusters are paramagnetic. The [TM(FeCp2)]∞ sandwich nanowires are ferromagnetic semiconductors whose band gap is 0.361, 0.506, 0.51, and 1.310 eV, respectively, for TM = Ti, Sc, V, and Mn. Among the four sandwich nanowires, [V(FeCp2)]∞ nanowire possesses the highest magnetic moment (5 μB) per unit cell.Keywords: density functional theory; high magnetic moments; nanomagnetism; sandwich clusters and nanowires
Co-reporter:Guangfen Wu, Jinlan Wang, Xiuyun Zhang and Liyan Zhu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 17) pp:7052-7057
Publication Date(Web):2017-2-22
DOI:10.1021/jp8113732
We investigate the feasibility of bare and metal-coated boron buckyball B80 with M = Li, Na, K, Be, Mg, Ca, Sc, Ti, and V for hydrogen storage using density functional theory approach. We find that M = Ca or Sc are best candidates for hydrogen storage with moderate adsorption energy of H2 and with clustering of Sc or Ca on B80 surface avoided. We further address that an isolated cluster Ca12B80 (Sc12B80) can bind up to 66 (60) H2 molecules with an average binding energy of 0.096 (0.346) eV/H2, leading to a hydrogen storage capacity of 9.0 wt % (7.9 wt %). Two adsorption mechanisms, charge-induced dipole interaction and the Dewar−Kubas interaction, are demonstrated, and they are responsible for high hydrogen storage capacity of Ca12B80 and Sc12B80. Most interestingly, the hydrogen loaded B80Sc12−48H2 complex can further adsorb 12 H2 through charge-induced dipole interaction. In other words, these two mechanisms dominate the adsorption of different parts of H2 in the same cluster of Sc12B80−60H2.
Co-reporter:Liyan Zhu and Jinlan Wang
The Journal of Physical Chemistry C 2009 Volume 113(Issue 20) pp:8767-8771
Publication Date(Web):April 24, 2009
DOI:10.1021/jp9018298
Organometallic transition metal (TM, TM = Sc, Ti, V, Cr, and Mn)−borazine sandwich clusters and one-dimensional infinite sandwich molecular wires are systematically investigated using spin-polarized density functional theory. The TM−borazine sandwich clusters and molecular wires are all energetically stable, among which the Sc−, Ti−, and V−borazine are of relatively higher stability. The TM−borazine molecular wires show diverse electronic and magnetic properties similar to the TM−benzene molecular wires. The ground-state electronic structures of V− and Mn−borazine molecular wires are both robust half-metallic ferromagnets, indicating they are possible good candidates in spintronics.
Co-reporter:Xiuyun Zhang, Jinlan Wang and Xiao Cheng Zeng
The Journal of Physical Chemistry A 2009 Volume 113(Issue 18) pp:5406-5413
Publication Date(Web):April 8, 2009
DOI:10.1021/jp8064272
We have studied structural, electronic, and magnetic properties of transition-metal−fullerene complexes Vn(C60)m, (n, m) = (1, 1), (1, 2), (2, 3), (3, 4), (4, 4), by means of a density functional theory method. We have examined relative stabilities of complexes with different V−C60 binding sites (V atoms are bound to either pentagonal or hexagonal rings of C60) and with different stacking configurations (linear or nonlinear). The linearly stacked sandwichlike complexes with V atoms binding to hexagonal rings of C60 are the most stable for (n, m) = (n, n + 1), although nonlinearly stacked configurations can be energetically competitive. For (n, m) = (1, 1), the V atom tends to bind to a pentagonal ring of the C60 molecule. For (n, m) = (4, 4), a riceball-like structure is found to be the most stable. Except for (n, m) = (1, 1), the lowest-energy structures of the complexes are generally in their lowest spin states.
Co-reporter:Liyan Zhu, Jinlan Wang, Mingli Yang
Journal of Molecular Structure: THEOCHEM 2008 Volume 869(1–3) pp:37-40
Publication Date(Web):30 November 2008
DOI:10.1016/j.theochem.2008.08.026
We present density functional theory calculations on the size-dependent and element-dependent structural, energetic, and magnetic properties of cationic group VI transition metal (TM = Cr, Mo, and W)–benzene (Bz = C6H6) half-sandwich and sandwich clusters. The TMBz2+ sandwiches exhibit higher thermodynamic stability than the other complexes. A close correlation is found between the metal–ligand interactions and the spin multiplicities of the complexes. The cationic complexes are all magnetic and their magnetism mostly stems from the contribution of TM atoms, while very small moments are found on Bz.
Co-reporter:Huabing Shu, Yunhai Li, Shudong Wang and Jinlan Wang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 6) pp:NaN4550-4550
Publication Date(Web):2015/01/07
DOI:10.1039/C4CP05146G
Using density functional theory, the G0W0 method and Bethe–Salpeter equation calculations, we systematically explore the structural, electronic and optical properties of hydrogenated and fluorinated germanene. The hydrogenated/fluorinated germanene tends to form chair and zigzag-line configurations and its electronic and optical properties show close geometry dependence. The chair hydrogenated/fluorinated and zigzag-line fluorinated germanene are direct band-gap semiconductors, while the zigzag-line hydrogenated germanene owns an indirect band-gap. Moreover, the quasi-particle corrections are significant and strong excitonic effects with large exciton binding energies are observed. Moreover, the zigzag-line hydrogenated/fluorinated germanene shows highly anisotropic optical responses, which may be used as a good optical linear polarizer.
Co-reporter:Qian Chen and Jinlan Wang
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 41) pp:NaN17797-17797
Publication Date(Web):2013/09/02
DOI:10.1039/C3CP52391H
Room-temperature ferromagnetism (RTFM) has been achieved in rare earth (RE) element doped ZnO nanostructures, while the mechanism of RTFM is still under debate. In this work, we investigated the electronic structure and magnetic properties of Nd-doped ZnO nanowires, and the influence of oxygen vacancies by using ab initio calculations. The impurity Nd atoms prefer to substitute the surface Zn sites and be ferromagnetically coupled with a moment of ∼3.0 μB per Nd in the doped ZnO nanowires, through a superexchange interaction mediated by the oxygen ions. More interestingly, the surface oxygen vacancy can greatly enhance the stability of the ferromagnetic state via the “local carriers” of Nd- and Zn-s electrons, which accounts for the room-temperature ferromagnetism in the Nd-doped ZnO nanowires. This mechanism and analysis can be applied to other rare earth element doped semiconductor nanostructures.
Co-reporter:Yuming Chen, Lijuan Meng, Weiwei Zhao, Zheng Liang, Xing Wu, Haiyan Nan, Zhangting Wu, Shan Huang, Litao Sun, Jinlan Wang and Zhenhua Ni
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 39) pp:NaN21687-21687
Publication Date(Web):2014/08/26
DOI:10.1039/C4CP03386H
Bilayer graphene as a prototype of two-dimensional stacked material has recently attracted great attention. The twist angle between graphene layers adds another dimension to control its properties. In this study, we used Raman mapping to investigate the twist angle dependence of properties of twisted bilayer graphene (TBG) with irregular grains that was fabricated by chemical vapor deposition (CVD). Different Raman parameters including intensity, width, and position of G and 2D peaks were used to distinguish TBG with different twist angles. The statistical results from Raman imaging on the distribution of twist angle are consistent with the results from selected area election diffraction (SAED). Finally, the Raman peak at approximately 1347 cm−1 for TBG with a large twist angle was assigned to the D-like peak, although it has similar excitation energy dependence of frequency as the defect-induced D peak. Theoretical calculation further confirmed that vacancy-like defect is not favored in the formation energy for TBG with a large twist angle as compared to monolayer graphene or TBG with other twist angles. These results will help to advance the understanding of TBG properties, especially for CVD samples with irregular grains.
Co-reporter:Xiaojing Yao, Xiuyun Zhang, Xiaoshan Ye and Jinlan Wang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 32) pp:NaN22398-22398
Publication Date(Web):2016/07/18
DOI:10.1039/C6CP03705D
Tuning the electronic and magnetic properties of graphene is a crucial problem in the design of practical on–off electronic devices. Using density functional theory calculations, we explore the electronic and magnetic properties of bilayer graphene functionalized by cyclopentadienyl (Cp = cyclopentadienyl, C5H5) based half-sandwich ligands, CpTM (TM = Sc–Ni). It is found that the adsorption of CpTM ligands can introduce high magnetic moments and open the band gap of bilayer graphene, due to the electron doping as well as the asymmetric charge distribution between two graphene layers. Furthermore, the p–n doping of bilayer graphene by co-binding F/NO2 and CpTM on two external sides of BLG can further widen the band gap up to 366.1 meV. This study proposes an effective way to the modulation of the electronic and magnetic properties of graphene.
Co-reporter:Huabing Shu, Yunhai Li, Xianghong Niu and Jinlan Wang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 8) pp:NaN6091-6091
Publication Date(Web):2016/01/26
DOI:10.1039/C5CP07995K
By employing density-functional theory, the G0W0 method and Bethe–Salpter equation, we explore quasi-particle energy bands, optical responses and excitons of bilayer black phosphorus (BBP) with four different stacking patterns. All the structures are direct band gap semiconductors and the band gap is highly dependent on the stacking pattern, with a maximum of 1.31 eV for AB-stacking and a minimum of 0.92 eV for AD-stacking. Such dependence can be well understood by the tight-binding model in terms of the interlayer hopping. More interestingly, stacking sensitive optical absorption and exciton binding energy are observed in BBPs. For x-polarized light, more red-shift of optical adsorption appears in AA-stacking and the strong exciton binding energy in the AA-stacking bilayer can be as large as 0.82 eV, that is ∼1.7 times larger than that of AD-stacking bilayer.
Co-reporter:Xianghua Zeng, Xiaojing Yao, Junyong Zhang, Qi Zhang, Wenqian Wu, Aihua Chai, Jinlan Wang, Qingdao Zeng and Jingli Xie
Inorganic Chemistry Frontiers 2015 - vol. 2(Issue 2) pp:NaN169-169
Publication Date(Web):2014/12/19
DOI:10.1039/C4QI00227J
A series of chalcogenide compounds with various compositions, i.e., octanuclear or tetranuclear Zn–S clusters, have been synthesised in a straighforward manner. Different fused-ring aromatic ligands were used as capping ligands and the corresponding zero-dimensional (0D) products were obtained. On the other hand, use of bridging ligands led to a family of one-dimensional (1D) coordination polymers, and an in situ ligand reaction has been observed in [Zn8S(SC6H5)13L1(H2O)]·2H2O (L = 3-carboxypryidyl) due to the hydrolysis of the cyano group of 3-pyridinecarbonitrile. A very rare 1D helical-chain structure was observed in [Zn4(SC6H5)8L1] (L = 4,4′-bipyridyl), providing evidence of the character of bridging organic ligands in the corresponding crystalline materials. First-principles calculations on [Zn4(SC6H5)8L1] (L = 4,4′-bipyridyl) further revealed that the two cluster units could rotate freely about the C–C single bond over a broad range, eventually leading to the formation of a one-dimensional helical structure.
Co-reporter:Xiaojing Yao, Jinlan Wang, Gang Wu, Shermin S. Goh, Hongjun Zhu and Shuo-Wang Yang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 14) pp:NaN3591-3591
Publication Date(Web):2017/03/14
DOI:10.1039/C7TC00678K
Based on density functional theory (DFT) calculations, we studied a two-step surface reaction for fabricating conductive molecular wires on hydrogen-terminated Si(100)2 × 1 surfaces. The first step is the self-assembled growth of 1,3,5-triethynylbenzene (TEB) molecules and formation of aligned molecular arrays on a H–Si(100)2 × 1 surface, and the second step is the in situ polymerization of the adsorbed molecules with CO via formal [2 + 2 + 1] cycloaddition reactions to produce a surface-grafted molecular wire, which is chemically bonded to the Si surface and electronically interlinked. The newly formed polymer/Si(100)2 × 1 structure is semiconducting and can be tuned to be conductive by electron doping; in this structure the molecular wires are the sole conducting channels and the Si substrate retains its semiconducting characteristics. Such unique properties make these surface-grafted molecular wires or polymers potential candidates in molecular electronics.
