Metal-decorated graphene oxides: microstructure and electrical properties

Abstract

Graphene has attracted a great deal of interest due to its remarkable electrical and thermal properties. For a cheaper, simpler, more efficient and better yielding method of producing graphene, graphene oxide (GO) comes to the fore. Because GO has sp2- and sp3-hybridized carbon atoms in contrast with graphene, GO has various properties from insulator to semiconductor by controlling of the amount of sp3-bondings. Especially, recent advances in reduction technique introduce GO as an electronic, optoelectronic, and chemical sensing. Moreover, the surface of GO has many active sites to decorate metals due to their oxygen functional groups. These wrapping sites by functionalities enhance the coverage of metal nanoparticles. Metal decoration also can be a considered method controlling GOs properties due to the interaction between metal nanoparticles and oxygen functional groups of GO. Forming the oxidized metal interlayer at interface of metal and GO is occurred by metal decoration and hence the band gap of GO is changed by changing the amount of sp3-bondings. Metal nanoparticle can be decorated onto the surface of GO with covalent binding or weak interactions and controlling the properties of GO by changing the amount of sp3-bondings of GO. In the first part of thesis, we study the relationship between microstructures and electrical properties of metal decorated GO. The microstructures of metal nanoparticles are investigated using transmission electron microscopy and electrical properties of metal decorated GO are obtained by probe station. We found that Pd nanoparticles strongly interact with GO rather than Ag or Au nanoparticles. Thus, Pd nanoparticles on GO were decorated with specific growth direction and exert a strong influence on electrical properties related to the formation of PdO interlayers between Pd nanoparticles and the surface of GO. In the second part, we investigate the possibility of Pd decorated GO with strong interaction to apply hydrogen gas sensor and photocathode due to the changing the electric properties of Pd decorated GO. We found that the sensitivity in gas sensor and the onset potential in photocathode are related to the coverage of Pd nanoparticles on GO.