Comparison of chemical and physical reduction methods to prepare layered graphene by graphene oxide: optimization of the structural properties and tuning of energy band gap

Abstract

A systematic study to optimize the structural properties of graphene synthesized from modified graphene by both chemical and physical reduction methods were studied. In the chemical method, the two most common reducing agent hydrazine hydrate and sodium borohydride at different concentrations were used. In the physical method, two different samples were produced using a heat treatment at 200 °C in the presence of argon gas. Structural properties, morphology and functional groups of samples by SEM, TEM, XRD, FTIR, UV–Vis, PL and TGA were analyzed. The results show that graphene sheets have been produced in all methods. This study showed that modified graphene with hydrazine hydrate (3 ml per 100 mg of GO) has the best structural properties. The result of physical reduction method by heat treatment in argon gas showed the lowest energy gap among other samples. The PL emission spectroscopy showed the strong intensities at 500 and 600 nm due to the overlap of the second order emissions in the electron–hole recombination processes as results from different types of electronically excited states and physical reduction had minimum of intensity. The obtained graphene nano-sheets showed an energy band gap from 1.37 to 2.70 eV that is suggested as an application method in opening of the energy band gap. However, synthesized graphene by the chemical reduction method by hydrazine hydrate treatment has the better structure, but the physical reduction method is rapid and equally appropriate.