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Liu L, Hou S, Zhao X, Liu C, Li Z, Li C, Xu S, Wang G, Yu J, Zhang C, Man B. Role of Graphene in Constructing Multilayer Plasmonic SERS Substrate with Graphene/AgNPs as Chemical Mechanism-Electromagnetic Mechanism Unit. NANOMATERIALS 2020; 10:nano10122371. [PMID: 33260554 PMCID: PMC7760367 DOI: 10.3390/nano10122371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 11/27/2020] [Accepted: 11/27/2020] [Indexed: 12/29/2022]
Abstract
Graphene–metal substrates have received widespread attention due to their superior surface-enhanced Raman scattering (SERS) performance. The strong coupling between graphene and metal particles can greatly improve the SERS performance and thus broaden the application fields. The way in which to make full use of the synergistic effect of the hybrid is still a key issue to improve SERS activity and stability. Here, we used graphene as a chemical mechanism (CM) layer and Ag nanoparticles (AgNPs) as an electromagnetic mechanism (EM) layer, forming a CM–EM unit and constructing a multi-layer hybrid structure as a SERS substrate. The improved SERS performance of the multilayer nanostructure was investigated experimentally and in theory. We demonstrated that the Raman enhancement effect increased as the number of CM–EM units increased, remaining nearly unchanged when the CM–EM unit was more than four. The limit of detection was down to 10−14 M for rhodamine 6G (R6G) and 10−12 M for crystal violet (CV), which confirmed the ultrahigh sensitivity of the multilayer SERS substrate. Furthermore, we investigated the reproducibility and thermal stability of the proposed multilayer SERS substrate. On the basis of these promising results, the development of new materials and novel methods for high performance sensing and biosensing applications will be promoted.
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Affiliation(s)
- Lu Liu
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
| | - Shuting Hou
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
| | - Xiaofei Zhao
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
| | - Chundong Liu
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
| | - Zhen Li
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
| | - Chonghui Li
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
- Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China;
- Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany
| | - Shicai Xu
- Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China;
| | - Guilin Wang
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
| | - Jing Yu
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
| | - Chao Zhang
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
- Correspondence: (C.Z.); (B.M.)
| | - Baoyuan Man
- Collaborative Innovation Center of Light Manipulations and Applications, School of Physics and Electronics, Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250358, China; (L.L.); (S.H.); (X.Z.); (C.L.); (Z.L.); (C.L.); (G.W.); (J.Y.)
- Correspondence: (C.Z.); (B.M.)
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Yang W, Li Z, Lu Z, Yu J, Huo Y, Man B, Pan J, Si H, Jiang S, Zhang C. Graphene-Ag nanoparticles-cicada wings hybrid system for obvious SERS performance and DNA molecular detection. OPTICS EXPRESS 2019; 27:3000-3013. [PMID: 30732328 DOI: 10.1364/oe.27.003000] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 01/04/2019] [Indexed: 06/09/2023]
Abstract
In recent years, biomaterials have increasingly attracted attention on surface-enhanced Raman spectroscopy (SERS) due to their well Raman performance while metal particles are combined with biological substrates. Therefore, we propose an environmentally friendly substrate based on silver-plated cicada wings with seamless graphene layer (Gr-AgNPs-C.w.), which can be prepared with a simple and inexpensive method. Compared with AgNPs-C.w., Gr-AgNPs-C.w. hybrids show better SERS performance with high sensitivity, good uniformity and good stability with R6G detection. The minimum detected concentration can reach 10-15 M, and the value of R2 can reach 0.996, respectively. Theoretical simulation demonstrates the situation of electromagnetic field through COMSOL software. In addition, due to the affinity of graphene for biomolecules, we can successfully detect the DNA biomolecules through a simple process. Therefore, this cheap and efficient natural SERS substrate has great potential for a considerable number of biochemical SERS applications and can broaden the way in which multiple SERS platforms derived from other natural materials are prepared.
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Huang Y, Lin J, Liu L, Lu Q, Zhang X, Zhang G, Li D. Enhanced performance of graphene transparent conductive films by introducing SiO2 bilayer antireflection nanostructure. NEW J CHEM 2019. [DOI: 10.1039/c9nj03671g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The performance of graphene transparent conductive films (TCFs) can be greatly enhanced by introducing silica nanospheres/acid-catalyzed silica bilayer antireflection (AR) nanostructure.
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Affiliation(s)
- Yue Huang
- School of Chemistry and Molecular Engineering
- East China Normal University
- Shanghai 200241
- P. R. China
| | - Jiayi Lin
- School of Chemistry and Molecular Engineering
- East China Normal University
- Shanghai 200241
- P. R. China
| | - Liyue Liu
- School of Chemistry and Molecular Engineering
- East China Normal University
- Shanghai 200241
- P. R. China
| | - Qing Lu
- School of Chemistry and Molecular Engineering
- East China Normal University
- Shanghai 200241
- P. R. China
| | - Xiaoling Zhang
- School of Chemistry and Molecular Engineering
- East China Normal University
- Shanghai 200241
- P. R. China
| | - Ganghua Zhang
- Shanghai Key Laboratory of Engineering Materials Application and Evaluation
- Shanghai Research Institute of Materials
- Shanghai 200437
- P. R. China
| | - Dezeng Li
- School of Chemistry and Molecular Engineering
- East China Normal University
- Shanghai 200241
- P. R. China
- State Key Laboratory of Precision Spectroscopy
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Jiang T, Wang X, Tang S, Zhou J, Gu C, Tang J. Seed-mediated synthesis and SERS performance of graphene oxide-wrapped Ag nanomushroom. Sci Rep 2017; 7:9795. [PMID: 28852103 PMCID: PMC5574994 DOI: 10.1038/s41598-017-10262-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/07/2017] [Indexed: 11/24/2022] Open
Abstract
A facile seed-mediated method was developed to modify core-shell Ag nanosphere@PSPAA with another Ag layer for achieving an enhancement of their surface-enhanced Raman scattering (SERS) activity. Interestingly, an Ag bridge in the polymer shell connected the inner and outer Ag layers, resulting in a mushroom-like nanostructure. The outer Ag grew around the polymer shell to form the cap of the nanomushrooms (NMs) with the extension of the reaction time. The epitaxial growth mechanism of this novel nanostructure was investigated by tuning the type of seed from nanosphere to nanocube and nanorod. With the growth of the outer Ag cap, the SERS intensity of these Ag NMs increased significantly together with the red-shifting and broadening of their typical localized surface plasmon resonance band. Such a phenomenon can be attributed to the formation of SERS hotspots between the inner and outer Ag layers. The Ag NMs were then wrapped with a graphene oxide (GO) shell via static interactions. The GO-wrapped Ag NMs exhibited a further better SERS performance in terms of sensitivity, homogeneity and stability compared with non-wrapped ones, indicating that the heterostructure could be potentially useful for SERS-based immunoassay.
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Affiliation(s)
- Tao Jiang
- Institute of Photonics, Department of Microelectronic Science and Engineering, Faculty of Science, Ningbo University, Ningbo, 315211, P. R. China.
| | - Xiaolong Wang
- Institute of Photonics, Department of Microelectronic Science and Engineering, Faculty of Science, Ningbo University, Ningbo, 315211, P. R. China
| | - Shiwei Tang
- Institute of Photonics, Department of Microelectronic Science and Engineering, Faculty of Science, Ningbo University, Ningbo, 315211, P. R. China
| | - Jun Zhou
- Institute of Photonics, Department of Microelectronic Science and Engineering, Faculty of Science, Ningbo University, Ningbo, 315211, P. R. China
| | - Chenjie Gu
- Institute of Photonics, Department of Microelectronic Science and Engineering, Faculty of Science, Ningbo University, Ningbo, 315211, P. R. China
| | - Jing Tang
- Institute of Physics, Ningbo University of Technology, Ningbo, 315016, P. R. China
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Sun J, Finklea HO, Liu Y. Characterization and electrolytic cleaning of poly(methyl methacrylate) residues on transferred chemical vapor deposited graphene. NANOTECHNOLOGY 2017; 28:125703. [PMID: 28163262 DOI: 10.1088/1361-6528/aa5e55] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Poly(methyl methacrylate) (PMMA) residue has long been a critical challenge for practical applications of the transferred chemical vapor deposited (CVD) graphene. Thermal annealing is empirically used for the removal of the PMMA residue; however experiments imply that there are still small amounts of residues left after thermal annealing which are hard to remove with conventional methods. In this paper, the thermal degradation of the PMMA residue upon annealing was studied by Raman spectroscopy. The study reveals that post-annealing residues are generated by the elimination of methoxycarbonyl side chains in PMMA and are believed to be absorbed on graphene via the π-π interaction between the conjugated unsaturated carbon segments and graphene. The post-annealing residues are difficult to remove by further annealing in a non-oxidative atmosphere due to their thermal and chemical stability. An electrolytic cleaning method was shown to be effective in removing these post-annealing residues while preserving the underlying graphene lattice based on Raman spectroscopy and atomic force microscopy studies. Additionally, a solution-gated field effect transistor was used to study the transport properties of the transferred CVD graphene before thermal annealing, after thermal annealing, and after electrolytic cleaning, respectively. The results show that the carrier mobility was significantly improved, and that the p-doping was reduced by removing PMMA residues and post-annealing residues. These studies provide a more in-depth understanding on the thermal annealing process for the removal of the PMMA residues from transferred CVD graphene and a new approach to remove the post-annealing residues, resulting in a residue-free graphene.
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Affiliation(s)
- Jianbo Sun
- Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, United States of America
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Yue W, Tang C, Wang C, Bai C, Liu S, Xie X, Hua H, Zhang Z, Li D. An electricity-fluorescence double-checking biosensor based on graphene for detection of binding kinetics of DNA hybridization. RSC Adv 2017. [DOI: 10.1039/c7ra08246k] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In this paper, an electricity-fluorescence double-checking biosensor based on graphene materials has been presented for detection of DNA hybridization kinetics.
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Affiliation(s)
- Weiwei Yue
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Caiyan Tang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Chunxing Wang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Chengjie Bai
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Shuyi Liu
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Xiaohui Xie
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Hongling Hua
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Zhen Zhang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
| | - Dengwang Li
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology
- School of Physics and Electronics
- Shandong Normal University
- Jinan 250358
- P. R. China
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7
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Xu S, Man B, Jiang S, Wang J, Wei J, Xu S, Liu H, Gao S, Liu H, Li Z, Li H, Qiu H. Graphene/Cu nanoparticle hybrids fabricated by chemical vapor deposition as surface-enhanced Raman scattering substrate for label-free detection of adenosine. ACS APPLIED MATERIALS & INTERFACES 2015; 7:10977-87. [PMID: 25941901 DOI: 10.1021/acsami.5b02303] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We present a graphene/Cu nanoparticle hybrids (G/CuNPs) system as a surface-enhanced Raman scattering (SERS) substrate for adenosine detection. The Cu nanoparticles wrapped by a monolayer graphene shell were directly synthesized on flat quartz by chemical vapor deposition in a mixture of methane and hydrogen. The G/CuNPs showed an excellent SERS enhancement activity for adenosine. The minimum detected concentration of the adenosine in serum was demonstrated as low as 5 nM, and the calibration curve showed a good linear response from 5 to 500 nM. The capability of SERS detection of adenosine in real normal human urine samples based on G/CuNPs was also investigated and the characteristic peaks of adenosine were still recognizable. The reproducible and the ultrasensitive enhanced Raman signals could be due to the presence of an ultrathin graphene layer. The graphene shell was able to enrich and fix the adenosine molecules, which could also efficiently maintain chemical and optical stability of G/CuNPs. Based on the G/CuNPs system, the ultrasensitive SERS detection of adenosine in varied matrices was expected for the practical applications in medicine and biotechnology.
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Affiliation(s)
- Shicai Xu
- †College of Physics and Electronic Information, Shandong Provincial Key Laboratory of Functional Macromolecular Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China
| | - Baoyuan Man
- ‡College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Shouzhen Jiang
- ‡College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Jihua Wang
- †College of Physics and Electronic Information, Shandong Provincial Key Laboratory of Functional Macromolecular Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China
| | - Jie Wei
- §Department of Neurology, Dezhou People's Hospital, Dezhou 253014, China
| | - Shida Xu
- ∥Department of Internal Medicine, Dezhou People's Hospital, Dezhou 253014,China
| | - Hanping Liu
- †College of Physics and Electronic Information, Shandong Provincial Key Laboratory of Functional Macromolecular Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China
| | - Shoubao Gao
- ‡College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Huilan Liu
- †College of Physics and Electronic Information, Shandong Provincial Key Laboratory of Functional Macromolecular Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China
| | - Zhenhua Li
- †College of Physics and Electronic Information, Shandong Provincial Key Laboratory of Functional Macromolecular Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China
| | - Hongsheng Li
- ⊥Department of Radiation Oncology, Key Laboratory of Radiation Oncology of Shandong Province, Shandong Cancer Hospital and Institute, Jinan 250117, China
| | - Hengwei Qiu
- ‡College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
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Varghese JJ, Mushrif SH. First-principles investigation of the dissociation and coupling of methane on small copper clusters: Interplay of collision dynamics and geometric and electronic effects. J Chem Phys 2015; 142:184308. [DOI: 10.1063/1.4919948] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Jithin J. Varghese
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459, Singapore
| | - Samir H. Mushrif
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459, Singapore
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Yang C, Xu Y, Zhang C, Sun Z, Chen C, Li X, Jiang S, Man B. Facile synthesis 3D flexible core-shell graphene/glass fiber via chemical vapor deposition. NANOSCALE RESEARCH LETTERS 2014; 9:394. [PMID: 25170331 PMCID: PMC4141666 DOI: 10.1186/1556-276x-9-394] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Accepted: 07/20/2014] [Indexed: 05/30/2023]
Abstract
UNLABELLED Direct deposition of graphene layers on the flexible glass fiber surface to form the three-dimensional (3D) core-shell structures is offered using a two-heating reactor chemical vapor deposition system. The two-heating reactor is utilized to offer sufficient, well-proportioned floating C atoms and provide a facile way for low-temperature deposition. Graphene layers, which are controlled by changing the growth time, can be grown on the surface of wire-type glass fiber with the diameter from 30 nm to 120 um. The core-shell graphene/glass fiber deposition mechanism is proposed, suggesting that the 3D graphene films can be deposited on any proper wire-type substrates. These results open a facile way for direct and high-efficiency deposition of the transfer-free graphene layers on the low-temperature dielectric wire-type substrates. PACS 81.05.U-; 81.07.-b; 81.15.Gh.
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Affiliation(s)
- Cheng Yang
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, People’s Republic of China
| | - Yuanyuan Xu
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, People’s Republic of China
| | - Chao Zhang
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, People’s Republic of China
| | - Zhencui Sun
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, People’s Republic of China
| | - Chuansong Chen
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, People’s Republic of China
| | - Xiuhua Li
- Lishan College, Shandong Normal University, Jinan 250014, People’s Republic of China
| | - Shouzhen Jiang
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, People’s Republic of China
| | - Baoyuan Man
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, People’s Republic of China
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10
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Zhang C, Liu M, Man BY, Jiang SZ, Yang C, Chen CS, Feng DJ, Bi D, Liu FY, Qiu HW, Zhang JX. Facile fabrication of graphene-topological insulator Bi2Se3 hybrid Dirac materials via chemical vapor deposition in Se-rich conditions. CrystEngComm 2014. [DOI: 10.1039/c4ce01269k] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Direct deposition of a uniform and high-quality Bi2Se3 thin film on a graphene film (layer controlled) is performed using a catalyst-free vapor deposition system in a Se-rich environment.
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Affiliation(s)
- C. Zhang
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - M. Liu
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - B. Y. Man
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - S. Z. Jiang
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
- State Key Lab of Crystal Materials Shandong University
- Jinan, People's Republic of China
| | - C. Yang
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - C. S. Chen
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - D. J. Feng
- School of Information Science and Engineering
- Shandong University
- Jinan, People's Republic of China
| | - D. Bi
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - F. Y. Liu
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - H. W. Qiu
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
| | - J. X. Zhang
- College of Physics and Electronics
- Shandong Normal University
- Jinan, People's Republic of China
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