Papers by Keyword: Graphen

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Authors: Hua Lan Wang, Qing Li Hao, Xi Feng Xia, Zhi Jia Wang, Jiao Tian, Ji Hua Zhu, Chun Tang, Xin Wang
Abstract: A graphene oxide/polyaniline composite was synthesized by an in situ polymerization process. This product was simply prepared in an ethylene glycol medium, using ammonium persulfate as oxidant in ice bath. The composite was characterized by field emission scanning electron microscopy, transmission electron microscopy, X-Ray photoelectron spectroscopy, Raman spectroscopy and electrochemical test. The composite material showed a good electrochemical performance.
Authors: M. Johari Roudi, T. Mahmoodi
Abstract: Graphene is a 2D lattice of Carbon atoms which has a high potential to use it for hydrogen storage. In this paper we have studied theoretically the adsorption of hydrogen molecules on a single-layer graphene and we obtained the adsorption energy including optimized position and orientation of the hydrogen molecule with respect to the graphene surface in different points of the graphene lattice. We have done our calculations using Quantum-ESPRESSO code and applying pseudo-potential method in the framework of Density Functional Theory (DFT). We have used Local Density Approximation (LDA) for exchange correlation energy. Our result shows that adsorption energy is increased with decreasing the density of . However the maximum adsorption energy is occurred on the hollow position and for the surface homogenous arrangement.
Authors: Jing Man Han, Zhan Fang Ma
Abstract: A label-free immunosensor was developed to detect the presence of an antigen. This immunosensor was based on the modulation of the electrochemistry of the surface bound redox species thionine (Thi). The model antigen was carcinoembryonic antigen (CEA) and the model epitope was the antibody of CEA (anti-CEA). Glassy carbon electrode surfaces were first drop-coated with a mixture of graphene, Thi and Nafion and air-dried. The electrode surface was then electrodeposited in HAuCl4 solution to form Au nanoparticles (AuNPs). The resulted AuNPs were used to immobilize anti-CEA. Binding of CEA to the surface bound epitope resulted in the attenuation of the Thi electrochemistry. Under optimal conditions, the response of the label-free immunosensor had a liner range from 10 fg/mL to 100 ng/mL with a detection of 3.5 fg/mL (S/N=3).
Authors: S.R. Dhakate, N. Chauhan, S. Sharma, R.B. Mathur
Abstract: We report an easy and scaleable approach to produce single and double layer graphene (Gr)-sheet from re-exfoliation of expanded graphite (EG) with large area. Transmission and scanning electron microscopic observations show that the Gr-sheets have an area of ~ (12 x 10) μm2. Raman spectroscopy has confirmed the presence of single and double layer Gr-sheet with I2D/IG ratio as ~ 1.7. Scanning probe microscopy studies reveals that on re-exfoliation of EG, thickness of Gr-layer decreases from 6-7 nm to 0.8-1.1 nm. This infers that re-exfoliation overcomes the problem of insufficient oxidation or inadequate pressure buildup during heat treatment.
Authors: Wei Zhao, Qing Yuan Meng
Abstract: The adsorption of methane (CH4) molecule on the pristine and Al-doped (4, 8) graphene was investigated via the first-principles calculations. The results demonstrated that, in comparison to the adsorption of a CH4 molecule on the pristine graphene sheet, a relatively stronger adsorption was observed between the CH4 molecule and Al-doped graphene with a shorter adsorption distance, larger binding energy and more charge-transfer from the graphene surface to the CH4 molecule. Therefore, the Al-doped graphene can be expected to be a novel sensor for the detection of CH4 molecules in future applications.
Authors: J.S. Arellano
Abstract: In this theoretical study, the H2 adsorption is considered in a novel system formed by a (6,6) carbon nanotube fragment and a planar graphene layer portion, when they are separated 4.72 a.u., with both subsystems inside a cubic supercell box of 25 a.u. side. There is greater H2 adsorption inside the carbon nanotube than in the interstitial space between the graphene layer and the carbon nanotube. The results are compared with the way the H2 molecule is adsorbed upon a lonely graphene layer and inside or outside the (6,6) carbon nanotube. It is studied if in the interstitial space close to the middle point between the wall and the graphene layer the hydrogen molecule could be adsorbed with a greater binding energy that in any other case. This was not possible for the selected supercell, but there are given some suggestions to be explored (using a nanotube with smaller radii or increasing the size of the supercell), that perhaps can optimize the binding energy for H2 adsorption. A general result is that the size of the cubic supercell can be selected to confine not only hydrogen inside the carbon nanotube but also in the interstitial space between the carbon nanotube wall and the graphene layer. It is believed that the studied system or a modification of this could sooner or later be used in a competitive way in comparison with other H2 storage materials respect to the hydrogen adsorption and desorption process.
Authors: Ling Ling Luo, Xing Xing Gu, Jun Wu, Shu Xian Zhong, Jian Rong Chen
Abstract: Graphene for its unique physical structure, excellent mechanical, electrical and physical properties has been widely applied in nanoelectronics, microelectronics, energy storage material, composite materials and so on. In recent years, many researchers found graphene have outstanding adsorption capacity of contaminants in aqueous solution due to its high specific surface area. This paper summarized the graphene, graphene oxide and functionalized graphene removing various heavy metals in waste water.
Authors: Antoine Tiberj, Marta Martin, Nicolas Camara, P. Poncharal, T. Michel, J.L. Sauvajol, Phillippe Godignon, Jean Camassel
Abstract: We report an investigation of few layers graphene exfoliated on SiC. Using AFM and Raman spectroscopy, we find that the graphene thickness determined from the normalized intensity of Raman lines significantly depart from the one obtained using XPS.
Authors: Yuda Yürüm, Burcu Saner Okan, Firuze Okyay, Alp Yürüm, Fatma Dinç, Neylan Görgülü, Selmiye Alkan Gürsel
Abstract: Graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional 2D honeycomb lattice. The graphene sheets in graphite interact with each other through van der Waals forces to form layered structure. The first graphene sheets were obtained by extracting monolayer sheets from the three-dimensional graphite using a technique called micromechanical cleavage in 2004 [. There are numerous attempts in the literature to produce monolayer graphene sheets by the treatment of graphite. The first work was conducted by Brodie in 1859 and GO was prepared by repeated treatment of Ceylon graphite with an oxidation mixture consisting of potassium chlorate and fuming nitric acid [. Then, in 1898, Staudenmaier produced graphite oxide (GO) by the oxidation of graphite in concentrated sulfuric acid and nitric acid with potassium chlorate [. However, this method was time consuming and hazardous. Hummers and Offeman found a rapid and safer method for the preparation of GO and in this method graphite was oxidized in water free mixture of sulfuric acid, sodium nitrate and potassium permanganate [.
Authors: Yoshifumi Morita
Abstract: Our focus is on the graphene under a magnetic field with Landau levels i.e. quantum Hall regime where a ‘confining potential’ is imposed by a finite electric field. In our theory, the graphene is modelled by a conventional fermion on a honeycomb lattice and the finite electric field is by a static potential. We reveal the fate/breakdown of the quantum Hall regime. A possible candidate of this kind of system is a grapheneQuantumDot, which we also discussed in the light of our theory.
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