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901.
902.
Wei Sun Yuanyuan Zhang Xiuzhen Wang Xiaomei Ju Dan Wang Jie Wu Zhenfan Sun 《Electroanalysis》2012,24(10):1973-1979
By using a 1‐butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) as the working electrode, graphene (GR) nanosheets and silver nanoparticles (Ag NPs) were step by step electrodeposited on the surface of the CILE with potentiostatic method. The fabricated Ag/GR/CILE was used as a new platform for protein electrochemistry and hemoglobin (Hb) was immobilized on its surface with chitosan (CTS) as film forming material. In 0.1 mol/L phosphate buffer solution, a pair of well‐defined and quasi‐reversible redox peaks appeared on the CTS/Hb/Ag/GR/CILE with a formal peak potential of ?0.202 V (vs. SCE) and a peak‐to‐peak separation (ΔEp) of 68 mV, which indicated that direct electrochemistry of Hb was realized on the modified electrode. The results could be attributed to the synergistic effects of Ag NPs and GR nanosheets on the electrode surface, which provided a specific three‐dimensional structure with high conductivity and good biocompatibility. The Hb modified electrode showed excellent electrocatalysis to the reduction of trichloroacetic acid in the concentration range from 0.8 to 22.0 mmol/L with a detection limit of 0.42 mmol/L (3σ). Moreover, the modified electrode exhibited favorable reproducibility, long term stability and accuracy, with potential applications in the third‐generation electrochemical biosensor. 相似文献
903.
904.
《Ultrasonics sonochemistry》2014,21(3):1174-1181
The reduction of graphene oxide (GO) to graphene (rGO) was achieved by using 20 kHz ultrasound in l-ascorbic acid (l-AA, reducing agent) aqueous solutions under various experimental conditions. The effects of ultrasound power, ultrasound pulse mode, reaction temperature, pH value and l-AA amount on the rates of rGO formation from GO reduction were investigated. The rates of rGO formation were found to be enhanced under the following conditions: high ultrasound power, long pulse mode, high temperature, high pH value and large amount of l-AA. It was also found that the rGO formation under ultrasound treatment was accelerated in comparison with a conventional mechanical mixing treatment. The pseudo rate and pseudo activation energy (Ea) of rGO formation were determined to discuss the reaction kinetics under both treatment. The Ea value of rGO formation under ultrasound treatment was clearly lower than that obtained under mechanical mixing treatment at the same condition. We proposed that physical effects such as shear forces, microjets and shock waves during acoustic cavitation enhanced the mass transfer and reaction of l-AA with GO to form rGO as well as the change in the surface morphology of GO. In addition, the rates of rGO formation were suggested to be affected by local high temperatures of cavitation bubbles. 相似文献
905.
Hall effect measurements of a graphene-on-SiC system were carried out as a function of temperature (1.8–200 K) at a static magnetic field (0.5 T). With the analysis of temperature dependent single-field Hall data with the Simple Parallel Conduction Extraction Method (SPCEM), bulk and two-dimensional (2D) carrier densities and mobilities were extracted successfully. Bulk carrier is attributed to SiC substrate and 2D carrier is attributed to the graphene layer. For each SPCEM extracted carrier data, relevant three-dimensional or 2D scattering analyses were performed. Each SPCEM extracted carrier data were explained with the related scattering analyses. A temperature independent mobility component, which may related to an interaction between graphene and SiC, was observed for both scattering analyses with the same mobility limiting value. With the SPCEM, effective ionized impurity concentration of SiC substrate, extracted 2D-mobility, and sheet carrier density of the graphene layer are calculated with using temperature dependent static magnetic field Hall data. 相似文献
906.
We have studied spin-dependent electron tunneling through the Rashba barrier in a monolayer graphene lattices. The transfer matrix method, have been employed to obtain the spin dependent transport properties of the chiral particles. It is shown that graphene sheets in the presence of Rashba spin–orbit barrier will act as an electron spin-inverter. 相似文献
907.
Graphene/ZnO hybrid was used, for the first time, to fabricate a highly selective and sensitive graphene based gas sensor by a combination of electromechanical and electrochemical characteristics of the graphene. ZnO nanowires in our fabricated sensor have two important roles: as the reductant of graphene oxide to obtain graphene and as an efficient electromechanical actuator due to their piezoelectric properties. To investigate the operation of the fabricated sensor as a gas sensor, a selected set of chemical vapors were introduced to the structure. It was found that chemical vapors change the resonance frequency of the graphene/ZnO structure, as well as the electrical resistivity of the sensor. The observed variation of the mechanical and electrical characteristics of the graphene/ZnO in response to gas exposure entitles the graphene/ZnO based sensor as a highly selective/sensitive device for gas sensing applications with distinctive signatures for different gas species. 相似文献
908.
We consider a two-dimensional massless Dirac operator coupled to a magnetic field B and an electric potential V growing at infinity. We find a characterization of the spectrum of the resulting operator H in terms of the relation between B and V at infinity. In particular, we give a sharp condition for the discreteness of the spectrum of H beyond which we find dense pure point spectrum. 相似文献
909.
Jingfang Wang Shunlong Yang Deyin Guo Ping Yu Dan Li Jianshan Ye Lanqun Mao 《Electrochemistry communications》2009,11(10):1892-1895
This study compares the electrochemical activity of four kinds of carbon materials, i.e. single-walled carbon nanotubes (SWNTs), pristine graphene oxide nanosheets (GONs), chemically reduced GONs, and electrochemically reduced GONs, with potassium ferricyanide (K3Fe(CN)6), β-nicotinamide adenine dinucleotide (NADH) and ascorbic acid (AA) as the redox probes. Cyclic voltammetry (CV) results demonstrate that the electron transfer kinetics of the redox probes employed here at the carbon materials essentially depend on the kind of the materials, of which the redox processes of the probes at SWNTs and electrochemically reduced GONs are faster than those at the pristine and chemically reduced GONs. The different electron transfer kinetics for the redox probes at the carbon materials studied here could be possibly ascribed to the synergetic effects of the surface chemistry (e.g., C/O ratio, presence of quinone-like groups, surface charge, and surface cleanness) and conductivity of the materials. This study could be potentially useful for understanding the structure/property relationship of the carbon materials and, based on this, for screening and synthesizing advanced carbon materials for electrochemical applications. 相似文献
910.
Jane Yao Xiaoping Shen Bei Wang Huakun Liu Guoxiu Wang 《Electrochemistry communications》2009,11(10):1849-1852
An in situ chemical synthesis approach has been developed to prepare SnO2–graphene nanocomposite. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO2 nanoparticles (4–6 nm in size) on graphene matrix. The electrochemical reactivities of the SnO2–graphene nanocomposite as anode material were measured by cyclic voltammetry and galvanostatic charge/discharge cycling. The as-synthesized SnO2–graphene nanocomposite exhibited a reversible lithium storage capacity of 765 mAh/g in the first cycle and an enhanced cyclability, which can be ascribed to 3D architecture of the SnO2–graphene nanocomposite. 相似文献