Tuneable Physicochemical Properties of Thermally Annealed Graphene Oxide Powder and Thin Films.

The tuneability of oxygen containing groups in graphene oxide (GO) that controls physicochemical properties is highly desirable for device applications. In this context, the thermally reduced graphene oxide (r-GO) powders and spin coated thin films with varying sp2/sp3 carbon network have been prepared using highly exfoliated GO (synthesized using modified Hummer's method with an innovative conjunction of lyophilisation). The additional step of lyophilisation results in the formation of highly exfoliated and monodispersed GO nanosheets as evidenced from FESEM, TEM, XRD, and Raman, FT-IR and UV-Vis spectroscopy. Spectroscopic analysis revealed the systematic evolution of r-GO with tuneable structural, optical and electrical properties as results of varying annealing temperatures (100-400 °C), due to restoration of sp2 conducting carbon network i.e., the formation of new -C═C- network and Stones-Wales defect. The tuneability of physical properties is further corroborated by change in the resistance values, as evidenced through the current-voltage characteristics in GO thin film based lateral device structures with Ag and Al top contacts. Controlling physicochemical properties at relatively low processing temperature warrants the utilization of GO and r-GO in various electronic and optoelectronic devices.