Nonlinear variable band gap of reduced graphene oxide examined by in-situ absorption spectrum and light response

Abstract

The band gap of reduced graphene oxide, playing a key role in many application fields, could be controllably tuned by oxygen group. Otherwise, up to now, it is unclear for the relation between these two. Herein, it was addressed by analyzing the thermogravimetric analysis, fourier infrared spectroscopy, and in-situ infrared spectroscopy, a nonlinear variable band gap was confirmed by fitting Tauc plot and also by light responses of RGO detective devices. The results showed that the reduction of oxygen group strongly relies on the annealing temperature. Different oxygen groups were lost at different temperatures. The hydroxyl group and carboxyl groop was lost before 200 °C, the epoxy group and carbonyl group was lost between 200 and 400 °C, the C-OH was lost at 400–600 °C, which exactly led to nonlinear variable band gap from 1.9 eV to 0.9 eV. In addition, the nonlinear photoelectric response of RGO light detective device further proved that trend of band gap. Our work pave a way to deeply apply RGO into electronic fields.