Study on graphene sheet

Graphene

Graphene is a sheet of carbon of one atom thick having great scope for making molecular electronic devices of the future due to its unique electronic and mechanical properties. Graphene has an extremely high electrical conductivity and exceptional strength. It has not been clear to researchers whether various exceptional properties of graphene are due to intrinsic properties of graphene, or simply due to increased microscopic surface area. By carefully studying the electrochemical behaviour of individual monolayer graphene sheets with well-defined areas researchers at Cornell University have performed electrochemical measurements on individual pieces of monolayer grapheme and have removed these uncertainties.

Study

The Cornell researchers studied graphene samples made by mechanical exfoliation (the so-called "sticky-tape" technique) and those grown by chemical vapour deposition. In both cases, they found that the rate at which electrons from the chemical ferrocene methanol were transferred onto the surface of the graphene was more than 10 times faster than the rate at which they transfer onto bulk graphite (the material from which graphene is "shaved off"). Researchers were also able to detect molecules desorbing from the surfaces of individual monolayer graphene sheets in real time. The researchers were able to achieve these results because they succeeded in fabricating individual high-quality graphene sheets and use these sheets as electrodes. Because they were looking at the surface properties of graphene, the fabrication steps were optimized to minimize contamination on the material's surface. They made the metal electrodes contacting the graphene without exposing to the electrochemical solution used in the experiment which showed that the graphene surface was the only electrochemically active area during measurements and the same was confirmed by cyclic voltammetric measurements.

High reactivity

The scientists reasoned that the enhanced electron transfer rate is most likely related to the fact that graphene is more reactive because graphene sheets contain corrugations that are not present on the atomically flat surface of bulk graphite and these corrugations lead to strain in graphene sheets at the atomic scale, which, in turn, activates the graphene surface to chemical reactions. This finding could lead to practical applications in devices such as batteries and sensors. The researchers believe that due to such measurement, graphene might serve as an almost pure, atomically well-defined electrode – something that would eliminate the uncontrolled atomic-scale variations present in ordinary "disordered" metal electrodes.