Co-reporter:Shishu Zhang, Nannan Mao, Na Zhang, Juanxia Wu, Lianming Tong, and Jin Zhang
ACS Nano October 24, 2017 Volume 11(Issue 10) pp:10366-10366
Publication Date(Web):October 9, 2017
DOI:10.1021/acsnano.7b05321
The Raman tensor of a crystal is the derivative of its polarizability tensor and is dependent on the symmetries of the crystal and the Raman-active vibrational mode. The intensity of a particular mode is determined by the Raman selection rule, which involves the Raman tensor and the polarization configurations. For anisotropic two-dimensional (2D) layered crystals, polarized Raman scattering has been used to reveal the crystalline orientations. However, due to its complicated Raman tensors and optical birefringence, the polarized Raman scattering of triclinic 2D crystals has not been well studied yet. Herein, we report the anomalous polarized Raman scattering of 2D layered triclinic rhenium disulfide (ReS2) and show a large circular intensity differential (CID) of Raman scattering in ReS2 of different thicknesses. The origin of CID and the anomalous behavior in polarized Raman scattering were attributed to the appearance of nonzero off-diagonal Raman tensor elements and the phase factor owing to optical birefringence. This can provide a method to identify the vertical orientation of triclinic layered materials. These findings may help to further understand the Raman scattering process in 2D materials of low symmetry and may indicate important applications in chiral recognition by using 2D materials.Keywords: birefringence; circular intensity differential; polarized Raman scattering; rhenium disulfide; triclinic;
Co-reporter:Xin Gao, Huaying Ren, Jingyuan Zhou, Ran Du, Chen Yin, Rong Liu, Hailin Peng, Lianming Tong, Zhongfan Liu, and Jin Zhang
Chemistry of Materials July 25, 2017 Volume 29(Issue 14) pp:5777-5777
Publication Date(Web):June 27, 2017
DOI:10.1021/acs.chemmater.7b01838
Co-reporter:Jin Zhang;Banghua Peng;Yagang Yao
The Journal of Physical Chemistry C August 5, 2010 Volume 114(Issue 30) pp:12960-12965
Publication Date(Web):2017-2-22
DOI:10.1021/jp103731p
In this study, the effect of the Reynolds number (Re) and Richardson number (Ri) on the growth of well-aligned ultralong single-walled carbon nanotubes (SWNTs) has been systematically investigated. Smaller Re and larger Ri are favored for the growth of ultralong SWNTs by analyzing the fluid dynamical properties of chemical vapor deposition and the floating growth mode of ultralong SWNTs. Comparative experiments at different Re and Ri were carried out by altering the inner diameter of the quartz tube and gas flux in different growth processes. Growth results indicated that either reducing the gas flux or increasing the inner diameter of the tube, which corresponds to smaller Re or larger Ri, is beneficial for the growth of well-aligned ultralong SWNTs. On the other hand, too large a Ri, namely, a large buoyancy, is not suitable to grow parallel SWNT arrays for its disturbance to the laminar flow. The laminar flow and appropriate buoyancy are two vital factors for the growth of parallel and high-quality SWNT arrays.
Co-reporter:Jian Li, Xin Gao, Xin Jiang, Xu-Bing Li, Zhongfan Liu, Jin Zhang, Chen-Ho Tung, and Li-Zhu Wu
ACS Catalysis August 4, 2017 Volume 7(Issue 8) pp:5209-5209
Publication Date(Web):July 5, 2017
DOI:10.1021/acscatal.7b01781
Graphdiyne (GDY), with highly π-conjugated structure of sp2- and sp-hybridized carbons, has recently appeared as an allotropic form of carbon nanomaterials. However, the application of this material is far behind its sister graphene. Herein, we attempt to use GDY as catalyst–support to stabilize cobalt nanoparticles for oxygen evolution, which is considered as the bottleneck for water splitting. In terms of close interaction between metal ions and alkyne π-conjugated networks, the self-supported electrode is made in situ by a facile chemical reduction of Co2+ salt precursor in aqueous solution. The prepared 3D Cu@GDY/Co electrode shows high OER electrocatalytic activity with a small overpotential of nearly 0.3 V and a large unit mass activity of 413 A g–1 at 1.60 V vs RHE. In the course of 4 h electrolysis, the electrode maintains the relatively constant current density. Our results indicate that the GDY is a promising catalyst–support to stabilize metal NPs for oxygen evolution.Keywords: catalysis; catalyst−support; cobalt nanoparticles; graphdiyne; water oxidation;
Co-reporter:Rong Liu;Jingyuan Zhou;Xin Gao;Jiaqiang Li;Ziqian Xie;Zhenzhu Li;Shuqing Zhang;Lianming Tong;Zhongfan Liu
Advanced Electronic Materials 2017 Volume 3(Issue 11) pp:
Publication Date(Web):2017/11/01
DOI:10.1002/aelm.201700122
AbstractThe decontamination of water polluted with heavy metal ions is of worldwide concern. Among various treatment approaches to remove metal ions from water, adsorption is regarded as an efficient method, and a variety of materials have been applied as adsorbents for the removal of metal ions from polluted water. Recently, carbon nanomaterials have been examined as alternative adsorbents due to their high specific surface areas, high removal efficiency, and strong interactions with metal ions. Graphdiyne, a new kind of carbon allotrope composed of sp- and sp2-hybridized carbon atoms, has attracted great interest due to its impressive properties. Graphdiyne is considered to be a promising candidate for the adsorption of heavy metal ions as the acetylenic links in graphdiyne strongly interact with metal ions. Herein, graphdiyne is used as an adsorbent to remove lead ions from water. The interaction between lead ions and graphdiyne is explored by X-ray photoelectron spectroscopy and Raman spectroscopy. The maximum adsorption capacity calculated by the Langmuir isotherm model is 470.5 mg g−1. Graphdiyne is also synthesized on copper foam and used as a filter to eliminate lead ions from water. The filter shows high performance with a removal efficiency of 99.6% and can be recovered through treatment with acidic solution.
Co-reporter:Rong Liu;Xin Gao;Jingyuan Zhou;Hua Xu;Zhenzhu Li;Shuqing Zhang;Ziqian Xie;Zhongfan Liu
Advanced Materials 2017 Volume 29(Issue 18) pp:
Publication Date(Web):2017/05/01
DOI:10.1002/adma.201604665
Graphdiyne analogs, linked carbon monolayers with acetylenic scaffoldings, are fabricated by adopting low-temperature chemical vapor deposition which provides a route for the synthesis of two-dimensional carbon materials via molecular building blocks. The electrical conductivity of the as-grown films can reach up to 6.72 S cm−1. Moreover, the films show potential as promising substrates for fluorescence suppressing and Raman advancement.
Co-reporter:Zhe Zheng;Hehai Fang;Dan Liu;Zhenjun Tan;Xin Gao;Weida Hu;Hailin Peng;Lianming Tong;Wenping Hu
Advanced Science 2017 Volume 4(Issue 12) pp:
Publication Date(Web):2017/12/01
DOI:10.1002/advs.201700472
AbstractSemiconducting single-walled carbon nanotubes (s-SWNTs) are regarded as an important candidate for infrared (IR) optical detection due to their excellent intrinsic properties. However, the strong binding energy of excitons in s-SWNTs seriously impedes the development of s-SWNTs IR photodetector. This Communication reports an IR photodetector with highly pure s-SWNTs and γ-graphdiyne. The heterojunctions between the two materials can efficiently separate the photogenerated excitons. In comparison to device fabricated only with s-SWNTs, this IR detector shows a uniform response in the whole channel of the device. The response time is demonstrated to be below 1 ms. The optimal responsivity and detectivity approximately reach 0.4 mA W−1 and 5 × 106 cmHz1/2 W−1, respectively.
Co-reporter:Jiaqiang Li;Ziqian Xie;Yan Xiong;Zhenzhu Li;Qunxing Huang;Shuqing Zhang;Jingyuan Zhou;Rong Liu;Xin Gao;Changguo Chen;Lianming Tong;Zhongfan Liu
Advanced Materials 2017 Volume 29(Issue 19) pp:
Publication Date(Web):2017/05/01
DOI:10.1002/adma.201700421
β-Graphdiyne (β-GDY) is a member of 2D graphyne family with zero band gap, and is a promising material with potential applications in energy storage, organic electronics, etc. However, the synthesis of β-GDY has not been realized yet, and the measurement of its intrinsic properties remains elusive. In this work, β-GDY-containing thin film is successfully synthesized on copper foil using modified Glaser–Hay coupling reaction with tetraethynylethene as precursor. The as-grown carbon film has a smooth surface and is continuous and uniform. Electrical measurements reveal the conductivity of 3.47 × 10−6 S m−1 and the work function of 5.22 eV. TiO2@β-GDY nanocomposite is then prepared and presented with an enhancement of photocatalytic ability compared to pure TiO2.
Co-reporter:Wanying Lei;Gang Liu;Minghua Liu
Chemical Society Reviews 2017 vol. 46(Issue 12) pp:3492-3509
Publication Date(Web):2017/06/19
DOI:10.1039/C7CS00021A
Owing to its high charge-carrier mobility, tunable direct-bandgap and unique in-plane anisotropic structure, black phosphorus (BP), a rising star of post-graphene two-dimensional (2D) nanomaterials, has been intensively investigated since early 2014. To explore its full potential and push the limits, research into BP-based novel functional nanostructures (i.e., nanomaterials and nanodevices) by means of hybridization, doping, and functionalization is rapidly expanding. Indeed, the cutting-edge developments and applications of BP nanostructures have had a significant impact on a wide range of research areas, including field effect transistors, diodes, photodetectors, biomedicine, sodium-ion batteries, photocatalysis, electrocatalysis, memory devices, and more. This tutorial review summarizes the recent advances of BP nanostructures and outlines the future challenges and opportunities.
Co-reporter:Fangfang Cui;Cong Wang;Xiaobo Li;Gang Wang;Kaiqiang Liu;Zhou Yang;Qingliang Feng;Xing Liang;Zhongyue Zhang;Shengzhong Liu;Zhibin Lei;Zonghuai Liu;Hua Xu
Advanced Materials 2016 Volume 28( Issue 25) pp:5019-5024
Publication Date(Web):
DOI:10.1002/adma.201600722
Co-reporter:Xin Gao;Jingyuan Zhou;Ran Du;Ziqian Xie;Shibin Deng;Rong Liu;Zhongfan Liu
Advanced Materials 2016 Volume 28( Issue 1) pp:168-173
Publication Date(Web):
DOI:10.1002/adma.201504407
Co-reporter:Ran Du;Xin Gao;Qingliang Feng;Qiuchen Zhao;Pan Li;Shibin Deng;Liurong Shi
Advanced Materials 2016 Volume 28( Issue 5) pp:936-942
Publication Date(Web):
DOI:10.1002/adma.201504542
Co-reporter:Shibin Deng;Jingyi Tang;Lixing Kang;Yue Hu;Fengrui Yao;Qiuchen Zhao;Shuchen Zhang;Kaihui Liu
Advanced Materials 2016 Volume 28( Issue 10) pp:2018-2023
Publication Date(Web):
DOI:10.1002/adma.201505253
Co-reporter:Jian Li; Xin Gao; Bin Liu; Qingliang Feng; Xu-Bing Li; Mao-Yong Huang; Zhongfan Liu; Jin Zhang; Chen-Ho Tung;Li-Zhu Wu
Journal of the American Chemical Society 2016 Volume 138(Issue 12) pp:3954-3957
Publication Date(Web):March 10, 2016
DOI:10.1021/jacs.5b12758
Graphdiyne (GDY), a novel large π-conjugated carbon material, for the first time, is introduced as the hole transfer layer into a photoelectrochemical water splitting cell (PEC). Raman and ultraviolet photoelectron spectroscopic studies indicate the existence of relatively strong π–π interactions between GDY and 4-mercaptopyridine surface-functionalized CdSe quantum dots, beneficial to the hole transportation and enhancement of the photocurrent performance. Upon exposure to a Xe lamp, the integrated photocathode produces a current density of nearly −70 μA cm–2 at a potential of 0 V vs NHE in neutral aqueous solution. Simultaneously, the photocathode evolves H2 with 90 ± 5% faradic efficiency over three times and exhibits good stability within 12 h. All of the results indicate that GDY is a promising hole transfer material to fabricate a PEC device for water splitting by solar energy.
Co-reporter:Lixing Kang; Shuchen Zhang; Qingwen Li
Journal of the American Chemical Society 2016 Volume 138(Issue 21) pp:6727-6730
Publication Date(Web):May 13, 2016
DOI:10.1021/jacs.6b03527
Horizontally aligned semiconducting single-walled carbon nanotube (s-SWNT) arrays with a certain density are highly desirable for future electronic devices. However, obtaining s-SWNT arrays with simultaneously high purity and high density is extremely challenging. We report herein a rational approach, using ethanol/methane chemical vapor deposition, to grow SWNT arrays with a s-SWNT ratio over 91% and a density higher than 100 tubes/μm. In this approach, at a certain temperature, ethanol was fully thermally decomposed to feed carbon atoms for Trojan-Mo catalysts growing high density SWNT arrays, while the incomplete pyrolysis of methane provided appropriate active H radicals with the help of catalytic sapphire surface to inhibit metallic SWNT (m-SWNT) growth. The synergistic effect of ethanol/methane mixtures resulted in enriched semiconducting SWNTs and no obvious decrease in nanotube density due to their milder reactivity and higher controllability at suitable growth conditions. This work represents a step forward in large-area synthesis of high density s-SWNT arrays on substrates and demonstrates potential applications in scalable carbon nanotube electronics.
Co-reporter:Lixing Kang, Shibin Deng, Shuchen Zhang, Qingwen Li, and Jin Zhang
Journal of the American Chemical Society 2016 Volume 138(Issue 39) pp:12723-12726
Publication Date(Web):September 21, 2016
DOI:10.1021/jacs.6b06477
Small diameter single-walled carbon nanotube (SWNT) arrays with larger bandgap are more desirable as near-infrared optical absorbers for the fabrication of high performance photovoltaic and photodetector devices. We report herein a rational approach to selective growth of well-aligned subnanometer diameter (∼84% between 0.75 and 0.95 nm) SWNT arrays with a density of 0.3–0.5 tubes/μm on quartz surfaces using solid Mo2C catalysts for short-time growth by low carbon feeding in hydrogen-free CVD. These subnanometer diameter SWNTs have a narrow chirality distribution (the ratio of (8,4), (8,5) and (7,6) is higher than 73%). During nanotube growth, only small size Mo nanoparticles are carbonized into stable Mo2C for catalyzing the growth of SWNTs through low carbon feeding rate over short time in the hydrogen-free environment, whereas larger catalysts are inactive due to underfeeding. Meanwhile, solid Mo2C catalysts are effective in reducing the chirality distributions of the as-grown SWNTs. Additionally, combining an annealing process after loading catalyst on the sapphire substrates, the average density is increased to ∼15 tubes/μm while maintaining small diameter and narrow chirality distribution. Our results offer more choices for structurally controlled growth of aligned-SWNTs, with potential applications in nanoelectronics.
Co-reporter:Na Zhang, Lianming Tong, and Jin Zhang
Chemistry of Materials 2016 Volume 28(Issue 18) pp:6426
Publication Date(Web):September 5, 2016
DOI:10.1021/acs.chemmater.6b02925
Due to the single-molecule sensitivity and the capability of chemical fingerprints recognition, surface-enhanced Raman scattering (SERS) has been an attractive analytical technique used in various fields. However, SERS sensing still suffers from several problems, including the heterogeneous adsorption of molecules on SERS substrates, the spectral fluctuation of molecules, the photo/chemical reactions of molecules in direct contact with metal, and the continuum spectral background originated from fluorescence or photocarbonization. Such problems greatly hinder its practical applications, in particular, in SERS quantification. Graphene, the star of the two-dimensional (2D) materials family, can be used for Raman enhancement, termed as graphene-based surface-enhanced Raman scattering (G-SERS). In this review, we will introduce the discovery of graphene-enhanced Raman scattering (GERS), the chemical enhancement, and its extension to other 2D materials beyond graphene. Then we will concentrate on graphene-based SERS toward analytical applications—from graphene-veiled SERS to G-SERS tape for quantitative analysis.
Co-reporter:Ran Du, Qingliang Feng, Huaying Ren, Qiuchen Zhao, Xin Gao and Jin Zhang
Journal of Materials Chemistry A 2016 vol. 4(Issue 3) pp:938-943
Publication Date(Web):26 Nov 2015
DOI:10.1039/C5TA08723F
In the field of water remediation, a 3D hydrophobic material with both remote controllability and high oil adsorption performance is highly desirable. To achieve it, magnetic components and microstructures are most likely involved. However, the simple enrolling of magnetic materials always results in quite low adsorption capacity. Additionally, the control of microstructures on 3D materials is immature, which limits the improvement of water/oil selectivity and oil adsorption speed. Herein, we devised 0D/2D hybrid dimensional magnetic microstructures with a well-defined morphology on melamine foams, which provided magnetism for remote controllability and highly rough surfaces for substantially enhanced water/oil selectivity. Hence, the resultant materials acquired magnetic-driven properties and superhydrophobicity/superoleophilicity simultaneously. Thus, they possess controllable, ultrafast, and high throughput oil uptake ability and high oil/water separation performance. The present strategy may open a new avenue to devise high-performance magnetic 3D assemblies for water remediation.
Co-reporter:Ran Du, Qiuchen Zhao, Pan Li, Huaying Ren, Xin Gao, and Jin Zhang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 1) pp:1025
Publication Date(Web):December 21, 2015
DOI:10.1021/acsami.5b11341
A quartz fiber based 3D monolithic materials was fabricated, which combines ultrahigh thermostability, remote controllability, mechanical flexibility, high water/oil selectivity, high processing capacity, and regeneration ability. This material exhibited great potential in water remediation, such as large absorption capacity (50- to 172-fold weight gain) toward oil standing in front of all magnetic sorbents and remarkable oil/water separation performance.Keywords: magnetic; quartz fiber; superhydrophobic; thermostable; water remediation
Co-reporter:Shuqing Zhang
The Journal of Physical Chemistry C 2016 Volume 120(Issue 19) pp:10605-10613
Publication Date(Web):April 25, 2016
DOI:10.1021/acs.jpcc.5b12388
We systematically studied the Raman spectra of graphyne (GY) and graphdiyne (GDY), analyzing their features under mechanical strain by group theory and first-principles calculations. The G bands in GY and GDY were softened compared with that in graphene, which provides a fingerprint useful in detecting their synthesis. We established a unified formulation to describe the effects of both uniaxial and shear strains, and combined this with calculated results to reveal the relationship underlying the changes in Raman evolution under various strains. Each doubly degenerate mode splits into two branches under strain, both of which are red-shifted with tensile uniaxial strain, but one is red-shifted and the other is blue-shifted under shear strain. The splitting under shear strain is double that under uniaxial strain.
Co-reporter:Qiuchen Zhao;Ziwei Xu;Yue Hu;Feng Ding
Science Advances 2016 Volume 2(Issue 5) pp:
Publication Date(Web):
DOI:10.1126/sciadv.1501729
Enriching near-zigzag single-walled carbons, which have a small tube-catalyst interface, by a “tandem plate” CVD method.
Co-reporter:Xi Ling, Shengxi Huang, Shibin Deng, Nannan Mao, Jing Kong, Mildred S. Dresselhaus, and Jin Zhang
Accounts of Chemical Research 2015 Volume 48(Issue 7) pp:1862
Publication Date(Web):June 9, 2015
DOI:10.1021/ar500466u
Surface enhanced Raman scattering (SERS) is a popular technique to detect the molecules with high selectivity and sensitivity. It has been developed for 40 years, and many reviews have been published to summarize the progress in SERS. Nevertheless, how to make the SERS signals repeatable and quantitative and how to have deeper understanding of the chemical enhancement mechanism are two big challenges. A strategy to target these issues is to develop a Raman enhancement substrate that is flat and nonmetal to replace the conventional rough and metal SERS substrate. At the same time, the newly developed substrate should have a strong interaction with the adsorbate molecules to guarantee strong chemical enhancement. The flatness of the surface allows better control of the molecular distribution and configuration, while the nonmetal surface avoids disturbance of the electromagnetic mechanism.Recently, graphene and other two-dimensional (2D) materials, which have an ideal flat surface and strong chemical interaction with plenty of organic molecules, were developed to be used as Raman enhancement substrates, which can light up the Raman signals of the molecules, and these substrates were demonstrated to be a promising for microspecies or trace species detection. This effect was named “graphene enhanced Raman scattering (GERS)”. The GERS technique offers significant advantages for studying molecular vibrations due to the ultraflat and chemically inert 2D surfaces, which are newly available, especially in developing a quantitative and repeatable signal enhancement technique, complementary to SERS. Moreover, GERS is a chemical mechanism dominated effect, which offers a valuable model to study the details of the chemical mechanism.In this Account, we summarize the systematic studies exploring the character of GERS. In addition, as a practical technique, the combination of GERS with a metal substrate incorporates the advantages from both conventional SERS and GERS. The introduction of graphene to the Raman enhancement substrate extended SERS applications in a more controllable and quantitative way. Looking to the future, we expect the combination of the SERS concept with the GERS technology to lead to the solution of some important issues in chemical dynamics and in biological processes monitoring.
Co-reporter:Lixing Kang, Yue Hu, Lili Liu, Juanxia Wu, Shuchen Zhang, Qiuchen Zhao, Feng Ding, Qingwen Li, and Jin Zhang
Nano Letters 2015 Volume 15(Issue 1) pp:403-409
Publication Date(Web):December 24, 2014
DOI:10.1021/nl5037325
For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, techniques to obtain horizontally aligned semiconducting SWNTs (s-SWNTs) with higher densities are still in their infancy. We reported herein a rational approach for the preferential growth of densely packed and well-aligned s-SWNTs arrays using oxygen-deficient TiO2 nanoparticles as catalysts. Using this approach, a suitable concentration of oxygen vacancies in TiO2 nanoparticles could form by optimizing the flow rate of hydrogen and carbon sources during the process of SWNT growth, and then horizontally aligned SWNTs with the density of ∼10 tubes/μm and the s-SWNT percentage above 95% were successfully obtained on ST-cut quartz substrates. Theoretical calculations indicated that TiO2 nanoparticles with a certain concentration of oxygen vacancies have a lower formation energy between s-SWNT than metallic SWNT (m-SWNT), thus realizing the preferential growth of s-SWNT arrays. Furthermore, this method can also be extended to other semiconductor oxide nanoparticles (i.e., ZnO, ZrO2 and Cr2O3) for the selective growth of s-SWNTs, showing clear potential to the future applications in nanoelectronics.
Co-reporter:Shuchen Zhang; Lianming Tong; Yue Hu; Lixing Kang
Journal of the American Chemical Society 2015 Volume 137(Issue 28) pp:8904-8907
Publication Date(Web):July 10, 2015
DOI:10.1021/jacs.5b05384
Semiconducting single-walled nanotube (s-SWNT) arrays with specific diameters are urgently demanded in the applications in nanoelectronic devices. Herein, we reported that by using uniform Mo2C solid catalyst, aligned s-SWNT (∼90%) arrays with narrow-diameter distribution (∼85% between 1.0 and 1.3 nm) on quartz substrate can be obtained. Mo2C nanoparticles with monodisperse sizes were prepared by using molybdenum oxide-based giant clusters, (NH4)42[Mo132O372(H3CCOO)30(H2O)72]·10H3CCOONH4·300H2O(Mo132), as the precursor that was carburized by a gas mixture of C2H5OH/H2 during a temperature-programmed reduction. In this approach, the formation of volatile MoO3 was inhibited due to the annealing and reduction at a low temperature. As a result, uniform Mo2C nanoparticles are formed, and their narrow size-dispersion strictly determines the diameter distribution of SWNTs. During the growth process, Mo2C selectively catalyzes the scission of C–O bonds of ethanol molecules, and the resultant absorbed oxygen (Oads) preferentially etches metallic SWNTs (m-SWNTs), leading to the high-yield of s-SWNTs. Raman spectroscopic analysis showed that most of the s-SWNTs can be identified as (14, 4), (13, 6), or (10, 9) tubes. Our findings open up the possibility of the chirality-controlled growth of aligned-SWNTs using uniform carbide nanoparticles as solid catalysts for practical nanoelectronics applications.
Co-reporter:Shuchen Zhang; Yue Hu; Juanxia Wu; Dan Liu; Lixing Kang; Qiuchen Zhao
Journal of the American Chemical Society 2015 Volume 137(Issue 3) pp:1012-1015
Publication Date(Web):January 13, 2015
DOI:10.1021/ja510845j
For the application of single-walled carbon nanotubes (SWNTs) to electronic and optoelectronic devices, techniques to obtain semiconducting SWNT (s-SWNT) arrays are still in their infancy. We have developed herein a rational approach for the preferential growth of horizontally aligned s-SWNT arrays on a ST-cut quartz surface through the selective scission of C–O and C–C bonds of ethanol using bimetal catalysts, such as Cu/Ru, Cu/Pd, and Au/Pd. For a common carbon source, ethanol, a reforming reaction occurs on Cu or Au upon C–C bond breakage and produces Cads and CO, while a deoxygenating reaction occurs on Ru or Pd through C–O bond breaking resulting in the production of Oads and C2H4. The produced C2H4 by Ru or Pd can weaken the oxidative environment through decomposition and the neutralization of Oads. When the bimetal catalysts with an appropriate ratio were used, the produced Cads and C2H4 can be used as carbon source for SWNT growth, and Oads promotes a suitable and durable oxidative environment to inhibit the formation of metallic SWNTs (m-SWNTs). Finally, we successfully obtained horizontally aligned SWNTs on a ST-cut quartz surface with a density of 4–8 tubes/μm and an s-SWNT ratio of about 93% using an Au/Pd (1:1) catalyst. The synergistic effects in bimetallic catalysts provide a new mechanism to control the growth of s-SWNTs.
Co-reporter:Jingyuan Zhou; Xin Gao; Rong Liu; Ziqian Xie; Jin Yang; Shuqing Zhang; Gengmin Zhang; Huibiao Liu; Yuliang Li; Jin Zhang;Zhongfan Liu
Journal of the American Chemical Society 2015 Volume 137(Issue 24) pp:7596-7599
Publication Date(Web):June 5, 2015
DOI:10.1021/jacs.5b04057
Synthesizing graphdiyne with a well-defined structure is a great challenge. We reported herein a rational approach to synthesize graphdiyne nanowalls using a modified Glaser–Hay coupling reaction. Hexaethynylbenzene and copper plate were selected as monomer and substrate, respectively. By adjusting the ratio of added organic alkali along with the amount of monomer, the proper amount of copper ions was dissolved into the solution, thus forming catalytic reaction sites. With a rapid reaction rate of Glaser–Hay coupling, graphdiyne grew vertically at these sites first, and then with more copper ions dissolved, uniform graphdiyne nanowalls formed on the surface of copper substrate. Raman spectra, UV–vis spectra, and HRTEM results confirmed the features of graphdiyne. These graphdiyne nanowalls also exhibited excellent and stable field-emission properties.
Co-reporter:Jingjing Lin; Liangbo Liang; Xi Ling; Shuqing Zhang; Nannan Mao; Na Zhang; Bobby G. Sumpter; Vincent Meunier; Lianming Tong
Journal of the American Chemical Society 2015 Volume 137(Issue 49) pp:15511-15517
Publication Date(Web):November 19, 2015
DOI:10.1021/jacs.5b10144
Surface-enhanced Raman scattering (SERS) on two-dimensional (2D) layered materials has provided a unique platform to study the chemical mechanism (CM) of the enhancement due to its natural separation from electromagnetic enhancement. The CM stems from the charge interactions between the substrate and molecules. Despite the extensive studies of the energy alignment between 2D materials and molecules, an understanding of how the electronic properties of the substrate are explicitly involved in the charge interaction is still unclear. Lately, a new group of 2D layered materials with anisotropic structures, including orthorhombic black phosphorus (BP) and triclinic rhenium disulfide (ReS2), has attracted great interest due to their unique anisotropic electrical and optical properties. Herein, we report a unique anisotropic Raman enhancement on few-layered BP and ReS2 using copper phthalocyanine (CuPc) molecules as a Raman probe, which is absent on isotropic graphene and h-BN. According to detailed Raman tensor analysis and density functional theory calculations, anisotropic charge interactions between the 2D materials and molecules are responsible for the angular dependence of the Raman enhancement. Our findings not only provide new insights into the CM process in SERS, but also open up new avenues for the exploration and application of the electronic properties of anisotropic 2D layered materials.
Co-reporter:Nannan Mao; Jingyi Tang; Liming Xie; Juanxia Wu; Bowen Han; Jingjing Lin; Shibin Deng; Wei Ji; Hua Xu; Kaihui Liu; Lianming Tong
Journal of the American Chemical Society 2015 Volume 138(Issue 1) pp:300-305
Publication Date(Web):December 15, 2015
DOI:10.1021/jacs.5b10685
The striking in-plane anisotropy remains one of the most intriguing properties for the newly rediscovered black phosphorus (BP) 2D crystals. However, because of its rather low-energy band gap, the optical anisotropy of few-layer BP has been primarily investigated in the near-infrared (NIR) regime. Moreover, the essential physics that determine the intrinsic anisotropic optical property of few-layer BP, which is of great importance for practical applications in optical and optoelectronic devices, are still in the fancy of theory. Herein, we report the direct observation of the optical anisotropy of few-layer BP in the visible regime simply by using polarized optical microscopy. On the basis of the Fresnel equation, the intrinsic anisotropic complex refractive indices (n–iκ) in the visible regime (480–650 nm) were experimentally obtained for the first time using the anisotropic optical contrast spectra. Our findings not only provide a convenient approach to measure the optical constants of 2D layered materials but also suggest a possibility to design novel BP-based photonic devices such as atom-thick light modulators, including linear polarizer, phase plate, and optical compensator in a broad spectral range extending to the visible window.
Co-reporter:Liang Chen, Ran Du, Jin Zhang and Tao Yi
Journal of Materials Chemistry A 2015 vol. 3(Issue 41) pp:20547-20553
Publication Date(Web):20 Jul 2015
DOI:10.1039/C5TA04370K
Large-scale manipulation of the density (from 2.5 to 1327 mg cm−3) and wettability of carbon-based aerogels has been realized by delicately modulating the gelation, drying and post-treatment processes. An unexpected “Janus face” effect of pyrrole was revealed in the fabrication process. Pyrrole acts as a “spacer” at relatively low concentrations (<ca. 5 vol%), resulting in a decrease of the aerogel density; however, “linker” behaviour appears at higher concentrations (>ca. 5 vol%), leading to an increase of the aerogel density. By using systematic studies, the oil adsorption capacity of aerogels has been correlated with the aerogel density and surface wettability, which can guide the production of highly efficient sorbents. For example, a polydimethylsiloxane modified graphene nanoribbons aerogel with a density of 2.5 mg cm−3 was prepared and showed a remarkable adsorption capacity of up to 302 times for phenixin and 121 times for n-hexane its own weight, much higher than that of most carbonaceous sorbents previously reported. Furthermore, a proof-of-concept aerogel-based floating-type densitometer has also been proposed to expand the potential applications of aerogels.
Co-reporter:Ran Du;Zhe Zheng;Nannan Mao;Na Zhang;Wenping Hu
Advanced Science 2015 Volume 2( Issue 1-2) pp:
Publication Date(Web):
DOI:10.1002/advs.201400006
Co-reporter:Qingliang Feng, Nannan Mao, Juanxia Wu, Hua Xu, Chunming Wang, Jin Zhang, and Liming Xie
ACS Nano 2015 Volume 9(Issue 7) pp:7450
Publication Date(Web):June 10, 2015
DOI:10.1021/acsnano.5b02506
Transition-metal dichalcogenide (TMD) monolayer alloys are a branch of two-dimensional (2D) materials which can have large-range band gap tuning as the composition changes. Synthesis of 2D TMD monolayer alloys with controlled composition as well as controlled domain size and edge structure is of great challenge. In the present work, we report growth of MoS2(1–x)Se2x monolayer alloys (x = 0.41–1.00) with controlled morphology and large domain size using physical vapor deposition (PVD). MoS2(1–x)Se2x monolayer alloys with different edge orientations (Mo-zigzag and S/Se-zigzag edge orientations) have been obtained by controlling the deposition temperature. Large domain size of MoS2(1–x)Se2x monolayer alloys (x = 0.41–1.00) up to 20 μm have been obtained by tuning the temperature gradient in the deposition zone. Together with previously obtained MoS2(1–x)Se2x monolayer alloys (x = 0–0.40), the band gap photoluminescence (PL) is continuously tuned from 1.86 eV (i.e., 665 nm, reached at x = 0.00) to 1.55 eV (i.e., 800 nm, reached at x = 1.00). Additionally, Raman peak splitting was observed in MoS2(1–x)Se2x monolayer alloys. This work provides a way to synthesize MoS2(1–x)Se2x monolayer alloys with different edge orientations, which could be benefit to controlled growth of other 2D materials.Keywords: alloy; morphology; MoS2(1−x)Se2x; physical vapor deposition; Raman spectrum; tunable band gap;
Co-reporter:Yabin Chen and Jin Zhang
Accounts of Chemical Research 2014 Volume 47(Issue 8) pp:2273-2281
Publication Date(Web):June 13, 2014
DOI:10.1021/ar400314b
Well-aligned SWNT arrays with a high density and controlled structures are highly desirable for carbon nanoelectronics. We hope that the advanced methodology used here will promote their controlled preparation and provide insights into the growth mechanism of SWNTs.
Co-reporter:Qingliang Feng;Yiming Zhu;Jinhua Hong;Mei Zhang;Wenjie Duan;Nannan Mao;Juanxia Wu;Hua Xu;Fengliang Dong;Fang Lin;Chuanhong Jin;Chunming Wang;Liming Xie
Advanced Materials 2014 Volume 26( Issue 17) pp:2648-2653
Publication Date(Web):
DOI:10.1002/adma.201306095
Co-reporter:Yabin Chen;Yingying Zhang;Yue Hu;Lixing Kang;Shuchen Zhang;Huanhuan Xie;Dan Liu;Qiuchen Zhao;Qingwen Li
Advanced Materials 2014 Volume 26( Issue 34) pp:5898-5922
Publication Date(Web):
DOI:10.1002/adma.201400431
Single-walled carbon nanotubes (SWNTs) directly synthesized on surfaces are promising building blocks for nanoelectronics. The structures and the arrangement of the SWNTs on surfaces determine the quality and density of the fabricated nanoelectronics, implying the importance of structure controlled growth of SWNTs on surfaces. This review summarizes the recent research status in controlling the orientation, length, density, diameter, metallicity, and chirality of SWNTs directly synthesized on surfaces by chemical vapor deposition, together with a session presenting the characterization method of the chirality of SWNTs. Finally, the remaining major challenges are discussed and future research directions are proposed.
Co-reporter:Ran Du;Na Zhang;Hua Xu;Nannan Mao;Wenjie Duan;Jinying Wang;Qiuchen Zhao;Zhongfan Liu
Advanced Materials 2014 Volume 26( Issue 47) pp:8053-8058
Publication Date(Web):
DOI:10.1002/adma.201403058
Co-reporter:Jinying Wang, Shuqing Zhang, Jingyuan Zhou, Rong Liu, Ran Du, Hua Xu, Zhongfan Liu, Jin Zhang and Zhirong Liu
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 23) pp:11303-11309
Publication Date(Web):23 Apr 2014
DOI:10.1039/C4CP00539B
Two-dimensional (2D) materials composed of sp and sp2 carbon atoms (e.g., graphyne and graphdiyne) show many interesting properties. These materials can be constructed through alkyne homocoupling; however, the occurrence of various side reactions increases the difficulty of their synthesis and structural characterization. Here, we investigate the thermodynamic properties and vibrational spectra of several aryl-alkynes. Both homocoupling and side reactions are found to occur spontaneously at room temperature in terms of thermodynamics. The calculated Raman spectra of the homocoupling products show regular changes with increasing polymerization degree. By rationalizing the vibrational modes of various oligomers, the Raman spectrum of a 2D sp–sp2 carbon sheet is predicted; it exhibits three sharp peaks at 2241, 1560, and 1444 cm−1. Although the target and byproducts display similar vibrational modes, a combination of Raman and infrared spectroscopies can be used to differentiate them. The theoretical results are then used to analyze the structure of a synthesized sample and provide useful information.
Co-reporter:Mei Zhang, Juanxia Wu, Yiming Zhu, Dumitru O. Dumcenco, Jinhua Hong, Nannan Mao, Shibin Deng, Yanfeng Chen, Yanlian Yang, Chuanhong Jin, Sunil H. Chaki, Ying-Sheng Huang, Jin Zhang, and Liming Xie
ACS Nano 2014 Volume 8(Issue 7) pp:7130
Publication Date(Web):June 2, 2014
DOI:10.1021/nn5020566
Two-dimensional transition-metal dichalcogenide alloys have attracted intense attention due to their tunable band gaps. In the present work, photoluminescence, Raman scattering, and electrical transport properties of monolayer and few-layer molybdenum tungsten diselenide alloys (Mo1–xWxSe2, 0 ≤ x ≤ 1) are systematically investigated. The strong photoluminescence emissions from Mo1–xWxSe2 monolayers indicate composition-tunable direct band gaps (from 1.56 to 1.65 eV), while weak and broad emissions from the bilayers indicate indirect band gaps. The first-order Raman modes are assigned by polarized Raman spectroscopy. Second-order Raman modes are assigned according to its frequencies. As composition changes in Mo1–xWxSe2 monolayers and few layers, the out-of-plane A1g mode showed one-mode behavior, while B2g1 (only observed in few layers), in-plane E2g1, and all observed second-order Raman modes showed two-mode behaviors. Electrical transport measurement revealed n-type semiconducting transport behavior with a high on/off ratio (>105) for Mo1–xWxSe2 monolayers.Keywords: electrical property; photoluminescence; Raman effect; semiconductor alloy; transition-metal dichalcogenide; tunable band gap
Co-reporter:Juanxia Wu ; Hua Xu ; Weihua Mu ; Liming Xie ; Xi Ling ; Jing Kong ; Mildred S. Dresselhaus
The Journal of Physical Chemistry C 2014 Volume 118(Issue 7) pp:3636-3643
Publication Date(Web):January 28, 2014
DOI:10.1021/jp411573c
Stacking disorder will significantly modify the optical properties and interlayer coupling stretch of few-layer graphene. Here, we report the observation of the Raman breathing modes in the low-frequency range of 100–200 cm–1 in misoriented few-layer graphene on a SiO2/Si substrate. Two dominant Raman modes are identified. The one at ∼120 cm–1 is assigned as the Eg + ZO′ combination mode of the in-plane shear and the out-of-plane interlayer optical phonon breathing modes. Another peak at ∼182 cm–1 is identified as the overtone mode 2ZO′. The appearance of these Raman modes for different twist angles indicates that stacking disorder in few-layer graphene significantly alters the Raman feature, especially for those combination modes containing the interlayer breathing mode. Further investigation shows that the two Raman vibrational modes (∼120 and ∼182 cm–1) are strongly coupled to the excitation laser energy, but their frequencies are independent of the number of graphene layers before folding. The present work provides a sensitive way to study the phonon dispersion, electron–phonon interaction, and electronic band structure of misoriented graphene layers.
Co-reporter:Shibin Deng;Weigao Xu;Jinying Wang;Xi Ling;Juanxia Wu;Liming Xie
Nano Research 2014 Volume 7( Issue 9) pp:1271-1279
Publication Date(Web):2014 September
DOI:10.1007/s12274-014-0490-3
Graphene substrates have recently been found to generate Raman enhancement. Systematic studies using different Raman probes have been implemented, but one of the most commonly used Raman probes, rhodamine 6G (R6G), has yielded controversial results for the enhancement effect on graphene. Indeed, the Raman enhancement factor of R6G induced by graphene has never been measured directly under resonant excitation because of the presence of intense fluorescence backgrounds. In this study, a polarization-difference technique is used to suppress the fluorescence background by subtracting two spectra collected using different excitation laser polarizations. As a result, enhancement factors are obtained ranging between 1.7 and 5.6 for the four Raman modes of R6G at 611, 1,183, 1,361, and 1,647 cm−1 under resonant excitation by a 514.5 nm laser. By comparing these results with the results obtained under non-resonant excitation (632.8 nm) and pre-resonant excitation (593 nm), the enhancement can be attributed to static chemical enhancement (CHEM) and tuning of the molecular resonance. Density functional theory simulations reveal that the orbital energies and densities for R6G are modified by graphene dots.
Co-reporter:Weigao Xu;Jiaqi Xiao;Yanfeng Chen;Yabin Chen;Xi Ling
Advanced Materials 2013 Volume 25( Issue 6) pp:928-933
Publication Date(Web):
DOI:10.1002/adma.201204355
Co-reporter:Yabin Chen, Yue Hu, Mengxi Liu, Weigao Xu, Yanfeng Zhang, Liming Xie, and Jin Zhang
Nano Letters 2013 Volume 13(Issue 11) pp:5666-5671
Publication Date(Web):October 22, 2013
DOI:10.1021/nl403336x
Chiral structure determination of single-walled carbon nanotube (SWNT), including its handedness and chiral index (n,m), has been regarded as an intractable issue for both fundamental research and practical application. For a given SWNT, the n and m values can be conveniently deduced if an arbitrary two of its three crucial structural parameters, that is, diameter d, chiral angle θ, and electron transition energy Eii, are obtained. Here, we have demonstrated a novel approach to derive the (n,m) indices from the θ, d, and Eii of SWNTs. Handedness and θ were quickly measured based on the chirality-dependent alignment of SWNTs on graphite surface. By combining their measured d and Eii, (n,m) indices of SWNTs can be independently and uniquely identified from the (θ,d) or (θ,Eii) plots, respectively. This approach offers intense practical merits of high-efficiency, low-cost, and simplicity.
Co-reporter:Dr. Hua Xu;Juanxia Wu;Yabin Chen;Haoli Zhang; Jin Zhang
Chemistry – An Asian Journal 2013 Volume 8( Issue 10) pp:2446-2452
Publication Date(Web):
DOI:10.1002/asia.201300505
Abstract
We have explored an approach for the fabrication of intrinsic and hysteresis-free graphene field-effect transistors (FETs) and for the construction of graphene p–n junctions based on substrate engineering by hexagonal boron nitride (h-BN)/SiO2. The effect of various interfaces on the performance of the graphene FETs was systematically studied by constructing four types of graphene devices (graphene/SiO2 FETs, graphene/h-BN FETs, h-BN/graphene/SiO2 FETs, and h-BN/graphene/h-BN FETs). Graphene/SiO2 FETs and h-BN/graphene/SiO2 FETs always exhibit large hysteresis before and after annealing, whereas graphene/h-BN FETs and h-BN/graphene/h-BN FETs show intrinsic properties after annealing. Raman measurements also indicate that graphene on a SiO2 substrate contains large amounts of p-doping, whereas that on a h-BN substrate is intrinsic. Thus, the graphene/h-BN interface gives intrinsic and hysteresis-free graphene FETs, whilst the graphene/SiO2 interface affords p-doping and a hysteresis effect in the graphene FETs. This result is because h-BN serves as an insulation layer, which prevents charge trapping between the graphene and the charge traps at the graphene/SiO2 interface, which cause the hysteresis. In addition, the negligible electrostatic doping of h-BN into graphene also ensures the intrinsic and hysteresis-free properties of graphene/BN/SiO2 FETs. Moreover, benefitting from the p-doped and intrinsic features of graphene on SiO2 and h-BN substrates, respectively, large-scale graphene p–n junction superlattices with great potential difference are constructed and integrated into photodetector arrays by substrate engineering with h-BN/SiO2. Efficient hot carrier-assisted photocurrent was generated by laser excitation at the junction under ambient conditions.
Co-reporter:Xi Ling ; Juanxia Wu ; Liming Xie
The Journal of Physical Chemistry C 2013 Volume 117(Issue 5) pp:2369-2376
Publication Date(Web):January 14, 2013
DOI:10.1021/jp310564d
Graphene-enhanced Raman scattering (GERS), enhancing Raman signals on graphene surface, is an excellent approach to investigate the properties of graphene via the Raman enhancement effect. In the present study, we studied the graphene-thickness dependent GERS in detail. First, by keeping molecule density on few-layer graphene using vacuum thermal deposition method, GERS enhancement was found to be the same for all graphene layers (one to six layers). While adsorbing probe molecules by solution soaking, the GERS enhancing factor was different on monolayer and bilayer graphene. By soaking in low concentration solutions, the GERS intensity on bilayer graphene was stronger than that on monolayer graphene, whereas by soaking under high concentration solutions, the GERS intensity difference was much less for that on monolayer and on bilayer. Molecule density, molecular configuration, and GERS enhancing factor are further discussed for molecules on monolayer and bilayer graphene. It was finally concluded that the abnormal graphene-thickness dependence of GERS between monolayer and bilayer graphene was attributed to the different enhancement for GERS on monolayer and bilayer graphene. Monolayer and bilayer graphene have different electronic structure and then doping effect of probe molecules, which shifts the Fermi level of graphenes differently. As a result, monolayer and bilayer graphene have different energy band matching with the probe molecules, yielding different chemical enhancement.
Co-reporter:Jie Wang;Minghui Liang;Yan Fang;Tengfei Qiu;Linjie Zhi
Advanced Materials 2012 Volume 24( Issue 21) pp:2874-2878
Publication Date(Web):
DOI:10.1002/adma.201200055
Co-reporter:Guo Hong, Yabin Chen, Pan Li, Jin Zhang
Carbon 2012 Volume 50(Issue 6) pp:2067-2082
Publication Date(Web):May 2012
DOI:10.1016/j.carbon.2012.01.035
Thanks to the development of controlled synthesis techniques, carbon nanotubes, a 20-year-old material, are doing better at finding practical applications. The history of carbon nanotube growth with controlled structure is reviewed. There have been two main categories of catalysts used for carbon nanotube growth, metal and non-metal. For the metal catalysts, the growth process and the mechanism involved have been adequately discussed, with a widely accepted vapor–liquid–solid growth mechanism. The strategies for preparing single-walled carbon nanotube samples with well-defined structures such as geometry, length and diameter, electronic property, and chirality have been well developed based on the proposed mechanism. However, a clear mechanism is still being explored for non-metal catalysts with a hypothesis of a vapor–solid growth mechanism. Accordingly, the controlled growth of carbon nanotubes with a non-metal catalyst is still in its infancy. This review highlights the structure-control growth approach for carbon nanotubes using both metal and non-metal catalysts, and tries to give a full understanding of the possible growth mechanisms.
Co-reporter:Xi Ling, L. G. Moura, Marcos A. Pimenta, and Jin Zhang
The Journal of Physical Chemistry C 2012 Volume 116(Issue 47) pp:25112-25118
Publication Date(Web):November 2, 2012
DOI:10.1021/jp3088447
In the chemical enhancement mechanism for Raman scattering, the two types of charge-transfer models, the excited-state and the ground-state charge-transfer mechanisms, present the different dependence of the enhanced Raman signals on the excitation wavelength. To investigate the type of charge-transfer mechanism in graphene-enhanced Raman scattering (GERS), the Raman excitation profiles of the copper phthalocyanine (CuPc) molecule were obtained in the range of 545—660 nm. The profiles in the GERS system were fitted well with the function of the ordinary resonant Raman scattering expression, where the incident and scattered resonance peaks were well-distinguished with the energy difference equaling the energy of the molecular vibrations. This result meets the prediction of ground-state charge transfer, in which model the dependence of the enhanced Raman signals on the excitation wavelength is the same as that of the ordinary Raman scattering, and rules out the prediction of the excited-state charge transfer because of no the possible charge-transfer resonance peak observed. Therefore, the GERS was proved to be a ground-state charge-transfer mechanism. Meanwhile, because the Raman excitation profiles of molecule can be obtained in the GERS system easily, which is usually difficult to obtain due to the self-absorption of the molecules, GERS opens up a new way to suppress this effect. This work contributes the deeper understanding of the graphene-enhanced Raman scattering.
Co-reporter:Yabin Chen, Yue Hu, Yuan Fang, Pan Li, Chaoqun Feng, Jin Zhang
Carbon 2012 50(9) pp: 3295-3297
Publication Date(Web):
DOI:10.1016/j.carbon.2011.12.019
Co-reporter:Weigao Xu;Xi Ling;Jiaqi Xiao;Mildred S. Dresselhaus;Jing Kong;Hongxing Xu;Zhongfan Liu
PNAS 2012 Volume 109 (Issue 24 ) pp:
Publication Date(Web):2012-06-12
DOI:10.1073/pnas.1205478109
Surface enhanced Raman spectroscopy (SERS) is an attractive analytical technique, which enables single-molecule sensitive
detection and provides its special chemical fingerprints. During the past decades, researchers have made great efforts towards
an ideal SERS substrate, mainly including pioneering works on the preparation of uniform metal nanostructure arrays by various
nanoassembly and nanotailoring methods, which give better uniformity and reproducibility. Recently, nanoparticles coated with
an inert shell were used to make the enhanced Raman signals cleaner. By depositing SERS-active metal nanoislands on an atomically
flat graphene layer, here we designed a new kind of SERS substrate referred to as a graphene-mediated SERS (G-SERS) substrate.
In the graphene/metal combined structure, the electromagnetic “hot” spots (which is the origin of a huge SERS enhancement)
created by the gapped metal nanoislands through the localized surface plasmon resonance effect are supposed to pass through
the monolayer graphene, resulting in an atomically flat hot surface for Raman enhancement. Signals from a G-SERS substrate
were also demonstrated to have interesting advantages over normal SERS, in terms of cleaner vibrational information free from
various metal-molecule interactions and being more stable against photo-induced damage, but with a comparable enhancement
factor. Furthermore, we demonstrate the use of a freestanding, transparent and flexible “G-SERS tape” (consisting of a polymer-layer-supported
monolayer graphene with sandwiched metal nanoislands) to enable direct, real time and reliable detection of trace amounts
of analytes in various systems, which imparts high efficiency and universality of analyses with G-SERS substrates.
Co-reporter:Pan Li and Jin Zhang
Journal of Materials Chemistry A 2011 vol. 21(Issue 32) pp:11815-11821
Publication Date(Web):06 Jul 2011
DOI:10.1039/C1JM10399G
The coexistence of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) in grown samples remains an obstacle in the application of SWNTs in nano-electronics. We report herein a rational approach to prepare well-aligned s-SWNTs using water vapor as a weak oxidant to etch the m-SWNTs during or after SWNTs growth. Water vapor with controlled concentration is carried into the furnace by argon gas during or after the SWNTs growth. It is found that the oxidation temperature and the concentration of water have a clear effect on the destruction of m-SWNTs. During SWNT growth (temperature above 800 °C), the introduction of water at a certain concentration only etches the SWNTs with small diameters and shows no selectivity between m-SWNTs and s-SWNTs. After SWNT growth, the water can etch m-SWNTs effectively with optimized oxidation temperatures and water concentrations. Micro-Raman spectra and electrical transport characterization confirm the selective etching effects. The mechanism of the selective etching of SWNTs with water is discussed based on the electronic structures of SWNTs. Using this method, densely packed and well aligned semiconductor SWNT arrays can be obtained. We believe this selective etching approach would largely broaden the application of SWNTs, especially for future nano-electronic and molecular detection devices.
Co-reporter:Yabin Chen, Jin Zhang
Carbon 2011 Volume 49(Issue 10) pp:3316-3324
Publication Date(Web):August 2011
DOI:10.1016/j.carbon.2011.04.016
A rational approach is reported for the growth of single-walled carbon nanotubes (SWCNTs) with controlled diameters using SiO2 nanoparticles in a chemical vapor deposition system. The SiO2 nanoparticles with different sizes were prepared by thermal oxidation of 3-aminopropyltriethoxysilane (APTES) with different number of layers which were assembled on Si substrates. It was found that the size of SiO2 nanoparticles increased with the number of assembled APTES layers. Using these SiO2 nanoparticles as nucleation centers, the diameter distribution of as-grown SWCNTs were correlated with the size of SiO2 particles. In addition, both the classical longitudinal optical or transverse optical bands of SiC in in situ Raman spectra during the whole growth process and the Si 2p peak of SiC in the X-ray photoelectron spectra were not observed, suggesting that the carbon sources did not react with the SiO2 nanoparticles during the growth. Comparing to vapor–liquid–solid mechanism for metallic catalysts, vapor–solid mechanism is proposed which results in a lower growth rate when using SiO2 nanoparticles as nucleation centers.
Co-reporter:Banghua Peng, Shan Jiang, Yongyi Zhang, Jin Zhang
Carbon 2011 Volume 49(Issue 7) pp:2555-2560
Publication Date(Web):June 2011
DOI:10.1016/j.carbon.2011.02.045
We report herein a rational approach to increase the proportion of metallic carbon nanotubes (CNTs) in horizontally aligned ultralong CNT arrays by electric field-assisted chemical vapor deposition. In a gas flow-directed growth mode, the buoyancy caused by temperature differences near the substrate can lift catalyst particles or CNTs from the substrate into the laminar flow so that ultralong CNT arrays with mixed metallic (m-) and semiconducting (s-) CNTs can be obtained. It was verified that the percentage of m-CNTs was about 47% for pristine CNTs. When an electric field was introduced during CNT growth, the grown CNTs were polarized and the generated electric field force assisted them into the laminar flow. The greater polarizability of m-CNTs compared to s-CNTs resulted in more m-CNTs lifted and an increased m- to s-CNT ratio in the array. Measurements of CNT electrical properties showed that the percentage of m-CNTs could reach 80% when the electric field intensity was set at 200 V/cm.
Co-reporter:Guo Hong;Matthew Zhou;Ruoxing Zhang;Dr. Shimin Hou;Dr. Wonmook Choi;Dr. Yun Sung Woo;Dr. Jae-Young Choi;Dr. Zhongfan Liu;Dr. Jin Zhang
Angewandte Chemie International Edition 2011 Volume 50( Issue 30) pp:
Publication Date(Web):
DOI:10.1002/anie.201103519
Co-reporter:Guo Hong;Matthew Zhou;Ruoxing Zhang;Dr. Shimin Hou;Dr. Wonmook Choi;Dr. Yun Sung Woo;Dr. Jae-Young Choi;Dr. Zhongfan Liu;Dr. Jin Zhang
Angewandte Chemie 2011 Volume 123( Issue 30) pp:6951-6955
Publication Date(Web):
DOI:10.1002/ange.201101700
Co-reporter:Hua Xu, Liming Xie, Haoli Zhang, and Jin Zhang
ACS Nano 2011 Volume 5(Issue 7) pp:5338
Publication Date(Web):June 16, 2011
DOI:10.1021/nn103237x
We studied the modulation of Raman scattering intensities of molecules on graphene by tuning the graphene Fermi level with electrical field effect (EFE). A series of metal phthalocyanine (M-Pc) molecules (M = Mn, Fe, Co, Ni, Cu, Zn), which have different molecular energy levels, were used as probe molecules. The Raman intensities of all these M-Pc molecules become weaker when the graphene Fermi level is up-shifted by applying a positive gate voltage, while they become stronger when the graphene Fermi level is down-shifted by applying a negative gate voltage. However, this Raman intensity modulation only occurs when applying the gate voltage with a fast sweep rate, while it is nearly absent when applying the gate voltage with a slow sweep rate, which is likely due to the arising of the hysteresis effect in the graphene EFE. In addition, the Raman modulation ability for M-Pc molecules with smaller energy gaps is larger than that with larger energy gaps due to the difference in the energy alignment between graphene and these M-Pc molecules. Furthermore, this modulation shows the greatest one on single-layer graphene and mainly comes from the first layer of molecules which are in direct contact with graphene. The Raman modulation of molecules in GERS with the EFE suggests that the Raman enhancement for GERS occurs through a chemical enhancement mechanism.Keywords: chemical enhancement; electric field modulation; graphene Fermi level
Co-reporter:Guo Hong;Matthew Zhou;Ruoxing Zhang;Dr. Shimin Hou;Dr. Wonmook Choi;Dr. Yun Sung Woo;Dr. Jae-Young Choi;Dr. Zhongfan Liu;Dr. Jin Zhang
Angewandte Chemie 2011 Volume 123( Issue 30) pp:
Publication Date(Web):
DOI:10.1002/ange.201103519
Co-reporter:Xi Ling
The Journal of Physical Chemistry C 2011 Volume 115(Issue 6) pp:2835-2840
Publication Date(Web):January 20, 2011
DOI:10.1021/jp111502n
Graphene-enhanced Raman scattering (GERS) has been discovered, and the chemical enhancement mechanism based on charge transfer was thought as the main reason for the enhancement. We reported herein the effect of an interference phenomenon, a well-known reason for influencing the Raman scattering intensity, on the GERS using SiO2/Si substrates with different SiO2 thicknesses. First, it was found that the variation of Raman intensity of graphene on different thicknesses of SiO2/Si substrates followed the interference law. When the GERS system was moved on these substrates, where copper phthalocyanine (CuPc) and protoporphyrin IX (PPP) were constructed on graphene, the variation of the Raman intensity of the molecules on graphene and on SiO2/Si substrate also followed the interference law well. However, for the GERS system, the Raman intensity of the molecules is obviously enhanced compared to the molecules on SiO2/Si substrates. The results show that when we compare the Raman scattering intensity of the molecule in the GERS system and non-GERS system on a SiO2/Si substrate with the same SiO2 thickness, an interference phenomenon will not influence the comparison of the intensity. Meanwhile, charge transfer between graphene and the molecule is proven existent regardless of the thick SiO2/Si substrate on which GERS occurs, by comparing the G-band shift of graphene before and after the deposition of the molecule, which further indicates the interaction between the molecule and graphene plays an important role in GERS. This work will be beneficial for the further understanding of the origin of GERS.
Co-reporter:Guo Hong;Matthew Zhou;Ruoxing Zhang;Dr. Shimin Hou;Dr. Wonmook Choi;Dr. Yun Sung Woo;Dr. Jae-Young Choi;Dr. Zhongfan Liu;Dr. Jin Zhang
Angewandte Chemie International Edition 2011 Volume 50( Issue 30) pp:6819-6823
Publication Date(Web):
DOI:10.1002/anie.201101700
Co-reporter:Xi Ling, Liming Xie, Yuan Fang, Hua Xu, Haoli Zhang, Jing Kong, Mildred S. Dresselhaus, Jin Zhang and Zhongfan Liu
Nano Letters 2010 Volume 10(Issue 2) pp:553-561
Publication Date(Web):December 29, 2009
DOI:10.1021/nl903414x
Graphene is a monolayer of carbon atoms packed into a two-dimensional (2D) honeycomb crystal structure, which is a special material with many excellent properties. In the present study, we will discuss the possibility that graphene can be used as a substrate for enhancing Raman signals of adsorbed molecules. Here, phthalocyanine (Pc), rhodamine 6G (R6G), protoporphyin IX (PPP), and crystal violet (CV), which are popular molecules widely used as a Raman probe, are deposited equally on graphene and a SiO2/Si substrate using vacuum evaporation or solution soaking. By comparing the Raman signals of molecules on monolayer graphene and on a SiO2/Si substrate, we observed that the intensities of the Raman signals on monolayer graphene are much stronger than on a SiO2/Si substrate, indicating a clear Raman enhancement effect on the surface of monolayer graphene. For solution soaking, the Raman signals of the molecules are visible even though the concentration is low to 10−8 mol/L or less. What’s more interesting, the enhanced efficiencies are quite different on monolayer, few-layer, multilayer graphene, graphite, and highly ordered pyrolytic graphite (HOPG). The Raman signals of molecules on multilayer graphene are even weaker than on a SiO2/Si substrate, and the signals are even invisible on graphite and HOPG. Taking the Raman signals on the SiO2/Si substrate as a reference, Raman enhancement factors on the surface of monolayer graphene can be obtained using Raman intensity ratios. The Raman enhancement factors are quite different for different peaks, changing from 2 to 17. Furthermore, we found that the Raman enhancement factors can be distinguished through three classes that correspond to the symmetry of vibrations of the molecule. We attribute this enhancement to the charge transfer between graphene and the molecules, which result in a chemical enhancement. This is a new phenomenon for graphene that will expand the application of graphene to microanalysis and is good for studying the basic properties of both graphene and SERS.
Co-reporter:Liming Xie, Shin G. Chou, Ajay Pande, Jayanti Pande, Jin Zhang, Mildred S. Dresselhaus, Jing Kong and Zhongfan Liu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 17) pp:7717-7720
Publication Date(Web):April 2, 2010
DOI:10.1021/jp9121497
Resonance Raman spectroscopy measurements of lysozyme-bound single-walled carbon nanotubes have been made during different stages of the chemically and thermally induced misfolding and of the denaturation process of nanotube-bound lysozymes. Changes to the Raman intensity of single-walled carbon nanotubes (SWNTs) have been observed during the denaturation of lysozyme. The Raman intensity changes are attributed to excitonic transition energy (Eii) shifts of the SWNTs during the denaturation of lysozyme. The Eii shift of SWNTs was confirmed by photoluminescence measurements.
Co-reporter:Yagang Yao;Xiaochuan Dai;Chaoqun Feng;Xuelei Liang;Li Ding;Wonmook Choi;Jae-Young Choi;Jong Min Kim;Zhongfan Liu
Advanced Materials 2009 Volume 21( Issue 41) pp:4158-4162
Publication Date(Web):
DOI:10.1002/adma.200901255
Co-reporter:Yagang Yao;Xiaochuan Dai;Chaoqun Feng;Xuelei Liang;Li Ding;Wonmook Choi;Jae-Young Choi;Jong Min Kim;Zhongfan Liu
Advanced Materials 2009 Volume 21( Issue 41) pp:
Publication Date(Web):
DOI:10.1002/adma.200990153
Co-reporter:Liming Xie, Hootan Farhat, Hyungbin Son, Jin Zhang, Mildred S. Dresselhaus, Jing Kong and Zhongfan Liu
Nano Letters 2009 Volume 9(Issue 5) pp:1747-1751
Publication Date(Web):March 30, 2009
DOI:10.1021/nl803004m
In this work, we carried out electroluminescence (EL) measurements on metallic single-walled carbon nanotubes (SWNTs) and compared the light emission from the suspended section with the on-substrate section along the same SWNT. In addition to the lowest excitonic emission for metallic SWNTs (M11), a side peak was observed at an energy of 0.17−0.20 eV lower than the M11 peak, which is attributed to a phonon-assisted sideband. Interestingly, this side peak was only observed from on-substrate sections but not from suspended sections. This is likely due to the higher electric field used in the EL measurement of on-substrate sections and the asymmetric surroundings for on-substrate SWNT sections. When the drain voltage is increased, either a blue shift or a red shift of the M11 emission (up to ±20 meV) was observed in different suspended SWNTs. The red shift can be explained by the temperature-dependence of the M11 transition energy, whereas the blue shift is surprising and has never been observed before. Some possible mechanisms for the blue shift are discussed.
Co-reporter:Yagang Yao, Chaoqun Feng, Jin Zhang and Zhongfan Liu
Nano Letters 2009 Volume 9(Issue 4) pp:1673-1677
Publication Date(Web):March 13, 2009
DOI:10.1021/nl900207v
Using the concept of “cloning”, we report herein a rational approach to grow single-walled carbon nanotubes (SWNTs) with controlled chirality via an open-end growth mechanism. Specifically, by using open-end SWNTs as “seeds/catalysts” (without metal catalysts), “new/duplicate” SWNTs could be grown and cloned from the parent segments via an open-end growth mechanism. Using this strategy, we have measured more than 600 short seed segments and have found that the yield of cloning is relatively low (around 9%). This yield can be greatly improved up to 40% by growing SWNTs on quartz substrate. Atomic force microscopy and micro resonance Raman spectroscopy characterization indicate that the parent nanotube and the duplicate nanotube have the same structure. These findings provide a potential approach for growing SWNTs with controlled chirality, which are important for the application of SWNTs in nanoelectronics.
Co-reporter:Liming Xie ; Xi Ling ; Yuan Fang ; Jin Zhang ;Zhongfan Liu
Journal of the American Chemical Society 2009 Volume 131(Issue 29) pp:9890-9891
Publication Date(Web):July 2, 2009
DOI:10.1021/ja9037593
We have measured resonance Raman spectra with greatly suppressed fluorescence (FL) background from rhodamine 6G (R6G) and protoporphyrin IX (PPP) adsorbed on graphene. The FL suppression is estimated to be ∼103 times for R6G. The successful observation of resonance Raman peaks demonstrates that graphene can be used as a substrate to suppress FL in resonance Raman spectroscopy (RRS), which has potential applications in low-concentration detection and RRS study of fluorescent molecules.
Co-reporter:Guo Hong ; Bo Zhang ; Banghua Peng ; Jin Zhang ; Won Mook Choi ; Jae-Young Choi ; Jong Min Kim ;Zhongfan Liu
Journal of the American Chemical Society 2009 Volume 131(Issue 41) pp:14642-14643
Publication Date(Web):September 24, 2009
DOI:10.1021/ja9068529
By introducing the UV beam into our homemade chemical vapor deposition system, we had obtained a well aligned SWNT array on an ST-cut quartz substrate. After transfer onto a SiO2/Si substrate, the SWNT array was detected by Raman spectroscopy and electrical measurement, which showed that over 95% of the SWNTs were semiconducting ones. It is proposed that the selection process took place at the very beginning of the SWNT formation rather than destroying the metallic SWNTs after growth. This approach has solved one of the most important problems in SWNT application.
Co-reporter:Chaoqun Feng;Yagang Yao;Zhongfan Liu
Nano Research 2009 Volume 2( Issue 10) pp:
Publication Date(Web):2009 October
DOI:10.1007/s12274-009-9054-3
Using carbon nanotubes as nanobarriers, the growth of single-walled carbon nanotubes (SWNTs) on a quartz surface can be terminated. First, carbon nanotube nanobarriers were grown on a quartz surface by the gas flow-directed growth mode. Then, the SWNTs were grown on the quartz surface via the lattice-oriented growth mode, in which growth of SWNTs can be terminated by hitting the nanotube nanobarriers. Moreover, using the carbon nanotube nanobarrier as a marker, the mechanism of the growth of SWNTs on the quartz surface can be studied; a base-growth mechanism is indicated. Based on this termination process and the base-growth mechanism, SWNT arrays with controlled lengths can be grown on a quartz surface by fixing the sites of both catalysts and nanobarriers.
Co-reporter:Yagang Yao, Xiaochuan Dai, Ran Liu, Jin Zhang and Zhongfan Liu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 30) pp:13051-13059
Publication Date(Web):July 1, 2009
DOI:10.1021/jp901366h
In the present study, we systematically described the tuning of the diameter of single-walled carbon nanotubes (SWNTs) from individual catalyst particle by temperature-mediated chemical vapor deposition (CVD). The basic idea is to change the temperature quickly during the growth of ultralong SWNTs via a “kite mechanism”. It has been found that the diameter of a SWNT varied with temperature oscillation; higher temperature led to thinner SWNTs with the same catalyst particle and lower temperature led to thicker ones. These diameter variations of SWNTs were measured by resonance Raman spectroscopy and atomic force microscopy (AFM). It has also been found that the diameter changes were highly related to their initial diameters. For each initial diameter, there are various probabilities of different diameter changes, but all of them are below a certain maximum, which depends on the initial diameter. The maximum diameter change reaches an extremum of 0.40 nm, while the initial diameter is around 1.6 nm, and the maximum diameter changes are much lower for nanotubes with a larger or smaller diameter, which implies that the diameter mediation by temperature is limited. Based on the results, a well-aligned individual ultralong SWNT array with a narrow diameter distribution of small diameter (around 1.0 nm) or larger diameter (around 2.0 nm) could be grown by ascending or descending temperature-mediated CVD, respectively. At the same time, a simple growth model supposing there is a graphene transition state when the tube formation is initiated is proposed to explain these phenomena. Under this model, the relationship between the growth temperature and the diameter of SWNTs was calculated. It has been found that, a catalyst particle with certain mole fraction of carbon will produce SWNTs with smaller diameter under higher growth temperature and vice versa. This trend accords well with our experimental data. Such diameter modulation of SWNTs by temperature would also help us to understand the CVD growth mechanism of SWNTs.
Co-reporter:Bo Zhang, Guo Hong, Banghua Peng, Jin Zhang, WonMook Choi, Jong Min Kim, Jae-Young Choi and Zhongfan Liu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 14) pp:5341-5344
Publication Date(Web):2017-2-22
DOI:10.1021/jp900499g
Large area, well-aligned single-walled carbon nanotubes (SWNTs) with node density up to 107/cm2 are prepared by a convenient one-step process, which is based on the two growth modes of carbon nanotubes: gas flow-directed growth mode and lattice-orientated growth mode. Carbon nanotubes cross-bar is realized by chemical vapor deposition approach where the direction of gas flow and the direction of lattice of the substrate (quartz) are perpendicular. Catalyst-pattern technique is applied to produce shipshape cross-bar structure, and optimum condition (especially growth temperature) for the process is carefully studied. Interaction between catalyst and substrate is identified as a critical factor for fabrication of SWNTs cross-bar for such interaction affects the length of lattice-orientated carbon nanotubes as well as the density of gas flow-directed carbon nanotubes. This growth phenomenon offers a capability to control the formation of the cross-bar structure.
Co-reporter:Bo Gao, Lai Jiang, Xi Ling, Jin Zhang and Zhongfan Liu
The Journal of Physical Chemistry C 2008 Volume 112(Issue 51) pp:20123-20125
Publication Date(Web):2017-2-22
DOI:10.1021/jp809374j
By using a homemade setup, the length of uniaxial strained single-walled carbon nanotubes (SWNTs) was directly measured by scanning electron microscopy (SEM), and quantitative relations between uniaxial strain and Raman frequency were obtained. It was found that RBM frequency was not affected, but G-band frequency variation was diameter and chirality-dependent under uniaxial strain. The G-band frequency shift rate increased with diameter increasing and chiral angel decreasing. Also G+ and G− frequency shift rates were related to chiral angle due to chirality-dependent C−C bonds elongation. A surprising finding that intermediate frequency mode (IFM) frequency upshifted with uniaxial strain increasing indicates that lattice transformation needs to be considered in phonon properties under uniaxial strain. These studies provide valuable information about geometric structure variation of SWNTs under uniaxial strain.
Co-reporter:Bo Gao ; Xiaojie Duan ; Jin Zhang ; Gang Wu ; Jinming Dong ;Zhongfan Liu
The Journal of Physical Chemistry C 2008 Volume 112(Issue 29) pp:10789-10793
Publication Date(Web):June 26, 2008
DOI:10.1021/jp803434y
Strain can effectively modulate the structure and properties of single-walled carbon nanotubes (SWNTs), and hence is an important aspect in their researches and applications. In this article, the effect of torsional strain on the G-band modes of individual SWNTs is reported. When torsional strain is induced by atomic force microscopy (AFM) manipulation, G-band of SWNTs varies significantly. Following G-band modes (2A1g, 2E1g, and 2E2g) assignment by polarized resonant Raman spectroscopy, it is found that modes with different symmetries respond quite differently to torsional strain. On the basis of the analyses of eight individual SWNTs, we find that the variation of G-band is sensitive to the diameter and chirality of SWNTs. Finally, the nonresonant Raman spectra of chiral (12, 4) SWNTs are calculated using the ab initio calculations and the empirical bond polarizability model, which further confirms that there are some relations between mode symmetries and the effect of torsional strain on Raman spectra.
Co-reporter:Bo Gao ; Yongyi Zhang ; Jin Zhang ; Jing Kong ;Zhongfan Liu
The Journal of Physical Chemistry C 2008 Volume 112(Issue 22) pp:8319-8323
Publication Date(Web):May 2, 2008
DOI:10.1021/jp800035s
Raman spectra of individual SWNTs were systematically investigated by comparing the behavior of 21 semiconducting and 32 metallic SWNTs. It is found that, compared to semiconducting SWNTs, the RBM of metallic ones is softened, which exhibits chirality dependence. There are significant differences in the line shape of the G-band between semiconducting and metallic SWNTs, which was attributed to electron–phonon coupling previously. However, we found that the differences cannot be explained only by the electron–phonon coupling via the Kohn anomaly mechanism. Curvature effect and other unknown reasons appear to also contribute to the dissimilarities. As for the D-band, the frequency of metallic SWNTs does not show a softening effect when compared with that of semiconducting SWNTs, which is not consistent with theoretical predictions.
Co-reporter:Wanying Lei, Gang Liu, Jin Zhang and Minghua Liu
Chemical Society Reviews 2017 - vol. 46(Issue 12) pp:NaN3509-3509
Publication Date(Web):2017/04/24
DOI:10.1039/C7CS00021A
Owing to its high charge-carrier mobility, tunable direct-bandgap and unique in-plane anisotropic structure, black phosphorus (BP), a rising star of post-graphene two-dimensional (2D) nanomaterials, has been intensively investigated since early 2014. To explore its full potential and push the limits, research into BP-based novel functional nanostructures (i.e., nanomaterials and nanodevices) by means of hybridization, doping, and functionalization is rapidly expanding. Indeed, the cutting-edge developments and applications of BP nanostructures have had a significant impact on a wide range of research areas, including field effect transistors, diodes, photodetectors, biomedicine, sodium-ion batteries, photocatalysis, electrocatalysis, memory devices, and more. This tutorial review summarizes the recent advances of BP nanostructures and outlines the future challenges and opportunities.
Co-reporter:Jinying Wang, Shuqing Zhang, Jingyuan Zhou, Rong Liu, Ran Du, Hua Xu, Zhongfan Liu, Jin Zhang and Zhirong Liu
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 23) pp:NaN11309-11309
Publication Date(Web):2014/04/23
DOI:10.1039/C4CP00539B
Two-dimensional (2D) materials composed of sp and sp2 carbon atoms (e.g., graphyne and graphdiyne) show many interesting properties. These materials can be constructed through alkyne homocoupling; however, the occurrence of various side reactions increases the difficulty of their synthesis and structural characterization. Here, we investigate the thermodynamic properties and vibrational spectra of several aryl-alkynes. Both homocoupling and side reactions are found to occur spontaneously at room temperature in terms of thermodynamics. The calculated Raman spectra of the homocoupling products show regular changes with increasing polymerization degree. By rationalizing the vibrational modes of various oligomers, the Raman spectrum of a 2D sp–sp2 carbon sheet is predicted; it exhibits three sharp peaks at 2241, 1560, and 1444 cm−1. Although the target and byproducts display similar vibrational modes, a combination of Raman and infrared spectroscopies can be used to differentiate them. The theoretical results are then used to analyze the structure of a synthesized sample and provide useful information.
Co-reporter:Pan Li and Jin Zhang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 32) pp:NaN11821-11821
Publication Date(Web):2011/07/06
DOI:10.1039/C1JM10399G
The coexistence of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) in grown samples remains an obstacle in the application of SWNTs in nano-electronics. We report herein a rational approach to prepare well-aligned s-SWNTs using water vapor as a weak oxidant to etch the m-SWNTs during or after SWNTs growth. Water vapor with controlled concentration is carried into the furnace by argon gas during or after the SWNTs growth. It is found that the oxidation temperature and the concentration of water have a clear effect on the destruction of m-SWNTs. During SWNT growth (temperature above 800 °C), the introduction of water at a certain concentration only etches the SWNTs with small diameters and shows no selectivity between m-SWNTs and s-SWNTs. After SWNT growth, the water can etch m-SWNTs effectively with optimized oxidation temperatures and water concentrations. Micro-Raman spectra and electrical transport characterization confirm the selective etching effects. The mechanism of the selective etching of SWNTs with water is discussed based on the electronic structures of SWNTs. Using this method, densely packed and well aligned semiconductor SWNT arrays can be obtained. We believe this selective etching approach would largely broaden the application of SWNTs, especially for future nano-electronic and molecular detection devices.
Co-reporter:Liang Chen, Ran Du, Jin Zhang and Tao Yi
Journal of Materials Chemistry A 2015 - vol. 3(Issue 41) pp:NaN20553-20553
Publication Date(Web):2015/07/20
DOI:10.1039/C5TA04370K
Large-scale manipulation of the density (from 2.5 to 1327 mg cm−3) and wettability of carbon-based aerogels has been realized by delicately modulating the gelation, drying and post-treatment processes. An unexpected “Janus face” effect of pyrrole was revealed in the fabrication process. Pyrrole acts as a “spacer” at relatively low concentrations (ca. 5 vol%), leading to an increase of the aerogel density. By using systematic studies, the oil adsorption capacity of aerogels has been correlated with the aerogel density and surface wettability, which can guide the production of highly efficient sorbents. For example, a polydimethylsiloxane modified graphene nanoribbons aerogel with a density of 2.5 mg cm−3 was prepared and showed a remarkable adsorption capacity of up to 302 times for phenixin and 121 times for n-hexane its own weight, much higher than that of most carbonaceous sorbents previously reported. Furthermore, a proof-of-concept aerogel-based floating-type densitometer has also been proposed to expand the potential applications of aerogels.
Co-reporter:Ran Du, Qingliang Feng, Huaying Ren, Qiuchen Zhao, Xin Gao and Jin Zhang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 3) pp:NaN943-943
Publication Date(Web):2015/11/26
DOI:10.1039/C5TA08723F
In the field of water remediation, a 3D hydrophobic material with both remote controllability and high oil adsorption performance is highly desirable. To achieve it, magnetic components and microstructures are most likely involved. However, the simple enrolling of magnetic materials always results in quite low adsorption capacity. Additionally, the control of microstructures on 3D materials is immature, which limits the improvement of water/oil selectivity and oil adsorption speed. Herein, we devised 0D/2D hybrid dimensional magnetic microstructures with a well-defined morphology on melamine foams, which provided magnetism for remote controllability and highly rough surfaces for substantially enhanced water/oil selectivity. Hence, the resultant materials acquired magnetic-driven properties and superhydrophobicity/superoleophilicity simultaneously. Thus, they possess controllable, ultrafast, and high throughput oil uptake ability and high oil/water separation performance. The present strategy may open a new avenue to devise high-performance magnetic 3D assemblies for water remediation.
![Benzene, 1,2,3,4,5,6-hexakis[2-(trimethylsilyl)ethynyl]-](/data/chemimg/137400/100516-62-9.png)
![Benzene, 1,2,3,4,5,6-hexakis[2-(trimethylsilyl)ethynyl]-](/data/chemimg/137400/100516-62-9_b.png)
