Article

Measurement of the quantum capacitance of graphene

Center for Bioelectronics and Biosensors, Biodesign Institute, Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287, USA.
Nature Nanotechnology (Impact Factor: 33.27). 09/2009; 4(8):505-9. DOI: 10.1038/nnano.2009.177
Source: PubMed

ABSTRACT Graphene has received widespread attention due to its unique electronic properties. Much of the research conducted so far has focused on electron mobility, which is determined by scattering from charged impurities and other inhomogeneities. However, another important quantity, the quantum capacitance, has been largely overlooked. Here, we report a direct measurement of the quantum capacitance of graphene as a function of gate potential using a three-electrode electrochemical configuration. The quantum capacitance has a non-zero minimum at the Dirac point and a linear increase on both sides of the minimum with relatively small slopes. Our findings -- which are not predicted by theory for ideal graphene -- suggest that charged impurities also influences the quantum capacitance. We also measured the capacitance in aqueous solutions at different ionic concentrations, and our results strongly indicate that the long-standing puzzle about the interfacial capacitance in carbon-based electrodes has a quantum origin.

Download full-text

Full-text

Available from: Nongjian Tao, Dec 31, 2014
2 Followers
 · 
483 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Graphene nanoscrolls (GNSs) as a new category of quasi one-dimensional (1D) belong to the carbon-based nanomaterials, which have recently captivated the attention of researchers. The latest discoveries of exceptional structural and electronic properties of GNSs like high mobility, controllable band gap, and tunable core size have become a great stimuli for graphene researchers. Due to the importance and critical role of nanoscale sensors and biosensors in medical facilities and human life, using a promising material like graphene has been widely studied to achieve better accuracy and sensitivity in these devices. Up until now, the majority of surveys conducted previously have focused on experimental studies for sensors family. Therefore, there is lake of analytical models in comparison to experimental surveys. In order to start and understand about the modelling of gas sensors structure, the field effect transistor(FET)-based structure is employed as a basic. In this study, graphene nanoscroll conductivity has been evaluated under the impacts which is induced by the adsorption of different values of NO2 gas concentration on GNS surface. So that, when GNS-gas sensor is exposed to NO2 gas molecules, the carrier concentration of GNS is changed which leads to the changes in the conductance, and consequently, in the current, this phenomenon is considered as sensing mechanism. The I–V characteristic of graphene nanoscroll-based gas sensor has been considered as a criterion to detect the effect of gas adsorption. In order to verify the accuracy of the proposed model, the results have been compared with the existing experimental work
    Plasmonics 03/2015; · 2.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Quantum capacitance of graphene plays a significant role for graphene's applications in electrochemical devices and sensors, while the determination of these basic characters of Dirac point, Fermi energy, quantum capacitance, etc is still a subject of considerable debate in both experiments and simulations. Here, we report joint first-principles/continuum calculations (JFPCCs) on a monolayer graphene electrode immersed in an electrolyte coupled with a reference electrode under an applied potential. The JFPCCs gave the Fermi level, charge density on graphene, Dirac point energy, electrostatic potential, electric double layer etc as a function of the applied potential with respect to the reference electrode. These results revealed the strongly coupled relationship between Fermi level change and Dirac point shift in electrochemical cell. The total capacitance of the electrochemical cell was dissected into the quantum capacitance of the graphene electrode and the capacitance of the electric double layer. Furthermore, simple and analytic formulas were proposed for the three capacitances, which predicted, in sufficient accuracy, the behavior of capacitance versus potential. These findings deepen the understanding of quantum capacitance of graphene, which will stimulate novel experimental and theoretical studies and boost the applications of graphene in electrochemical and energy areas.
    Electrochimica Acta 02/2015; 163. DOI:10.1016/j.electacta.2015.02.049 · 4.09 Impact Factor
  • Source