Study Of The Catalytic Capability And Surface States Modulation Of Graphene

Graphene, the two-dimensional sp2-hybridized carbon material, has a single-atom-thick and a honeycomb pattern, and the thickness of its layer is 0.34 nm. Graphene has a lot of potential applications, due to its excellent physical, electronic and chemical properties. Despite the great application potential, it is important that graphene has zero band gap as well as inertness to reaction, which are disadvantage to its application in the field of semiconductors and sensors. Moreover, the layers of graphene are easy to pile up and the solubility is small in common used solvents, which also weakens the competitive strength of graphene. The surface properties of graphene can be adjusted via functionalization and modification, which can enlarges the application range and offers opportunities for the development of functionalized graphene-based materials. In this thesis, we adjusted the surface states by doping and modification, thus improved the catalytic property of graphene.1. Electrochemical sensor based on nitrogen doped graphene:Simultaneous determination of ascorbic acid, dopamine and uric acid.Nitrogen doped graphene (NG) is an important modified graphene, which has special structural and electronic properties. In this chapter, we prepared NG by thermally annealing the mixture of graphite oxide and melamine, and the electrochemical sensor based on NG was constructed to simultaneously determine small biomolecules such as ascorbic acid (AA), dopamine (DA) and uric acid (UA) at pH 3.0-7.4. Due to its unique structure and electronic properties originating from nitrogen doping, NG shows high electrocatalytic activity towards the oxidation of AA, DA and UA. The electrochemical sensor shows a wide linear response for AA, DA and UA.These results demonstrate that NG is a promising candidate of advanced electrode material in electrochemical sensing and other electrocatalytic applications.2. The enhancement of photocatalysis in graphene oxide by modifying azobenzene.Azobenzene is a molecule which has reversible photo-isomerization between the stretched trans and the bent cis isomers under illumination, and has an intense absorption of light. Simultaneously, it has considerable changes in molecular shape, size, and dipole moments. Carbon nanomaterials/azobenzene moieties (Carbon-AZO) has been a new generation of photo-responsive hybrid in nanoelectronics, due to its optical and electronic properties. Graphene oxide (GO) has been a promising photocatalyst for CO2 to methanol conversion and hydrogen production from water, and the band gap of GO synthesized by a modified Hummers’ procedure is 2.4-4.3 eV. In this chapter, we found that GO was a weak photocatalysis for oxygen reduction. Then, the AuE/AuS surface was covalent attached 4,4’-Diaminoazobenzene and absorbed GO by π-π Interaction, and characterized by contact angle and Raman spectrum. Due to the intense light absorption of azobenzene, the photocatalysis signal of graphene oxide was enhanced from 0.2 nA to 25 nA. When benzidine with weaker light absorption was used as substitution of azobenzne, the photo response of the hybrid was reduced to 5 nA. These results demonstrate that the interaction of chemicals with intense light absorption may enhance the photocatalysis in graphene oxide.