Covalent functionalisation of graphene: novel approach to change electronic structure of graphene

Abstract

Graphene (GR) attracts increasing attention due to its unique physical and chemical properties, thus potential applications in optics and electronics. However the gapless band structure greatly limits its wide applications in optoelectronic devices. Surface functionalisation proves to be an effective method to tune the properties of graphene. In this study, hybrid GR materials with enhanced properties were achieved through GR surface functionalisation by using aryl diazonium salts of photosensitive azobenzene. Conformational transition from trans to cis states of azobenzenes induces hole doping in graphene through charge transfer. Significantly different from the pristine graphene, the graphene–azobenzene hybrids exhibited strong photoisomerisation of azobenzene between cis and trans forms under UV and visible light illumination. The large photoresponse obtained from the functionalised GR could be ascribed to the rigid chemical environment with azobenzene moieties chemically bonded onto the GR surface. Such surface functionalised GR hybrids with unique optical properties position them as promising materials for optoelectronic devices.

Keywords:

• Graphene
• Photosensitive azobenzene
• Covalent modification
• Raman spectroscopy