Reduced graphene oxide: Effect of reduction on electrical conductivity

In this study, the effect of reduction on the electrical conductivity of Graphene Oxide (GO) is investigated. The aim of this fabrication was to render electromagnetic interference (EMI) shielding to thin polymer films using GO as fillers. The electrical conductivity was determined using the four-probe method and shielding effectiveness was theoretically determined using the experimentally obtained conductivity values. The initial oxidation of graphite was performed using Hummers’ method and the oxidized GO was dispersed in water for further exfoliation by ultrasonication. Thin films of sonicated GO dispersions were solution casted and dried in a convection oven at 50^◦ C overnight. The dried films were treated with 48% hydrobromic acid (HBr), 95% hydrochloric acid (HCl) or 66% hydroiodic acid (HI) for 2 h, 24 h or 48 h. A partial factorial design of experiments based on Taguchi method was used to identify the best reducing agent to obtain maximum electrical conductivity in the partially reduced GO films. The experimental analysis indicates that the electrical resistivity of GO is highly dependent on the type of acid treatment and the samples treated with HI acid exhibited lowest resistivity of ~0.003 Ω·cm. The drop in resistivity value after chemical reduction was of the order of 10,000 times, and range obtained in this work is among the lowest reported so far. The theoretical EMI shielding of the reduced GO film provided a shielding effectiveness of 5.06 dB at 12 GHz.