From graphite to graphene: improving the Hummers method to produce high quality reduced graphene oxide (rGO)

Chemical exfoliation of graphite is one of the promising candidates for large-scale production of graphene-like materials.1 The modified Hummers method is a standard procedure for chemical exfoliation, it consists in three main steps (i) oxidation of graphite to obtain the graphite oxide followed by (ii) the dispersion of the graphite oxide in different solvents in order to produce homogeneous suspensions, and, finally (iii) the suspension reduction to obtain the reduced graphene oxide (rGO), which is a graphene derivative that presents vacancies and defects in its structure, inducing a decrease of several properties, e.g. electrical conductivity and thermal stability.2 To overcome the defect generation we present a simple approach in Hummers method, to obtain high quality rGO, based on a strict control of temperature and chemical addition ratio during the oxidation process, as described in step (i). Figure 1 summarizes our results and presents a comparison between the Raman results of a standard rGO and our procedure. The defect distance and the ID/IG ratio were calculated resulting in values to our material higher than 20 nm and 0.27 respectively, which could be comparable to CVD graphene. Also, we prepared flexibles thin films of rGO deposited over PET, which presented Rs values below 300 Ω/ with 75% of transmittance at 550 nm. Thus, we were able to produce rGO with characteristics similar to pristine graphene, through a simple route with high yield, promising to be employed in different graphene-based flexible devices.