Optimization of Reducing Agents for Selective Bandgap Manipulation in Visible Region of Graphene Oxide and Its Work Function Estimation

In the present study, we report an effective way for reduction of graphene oxide (GO) as well as tuning of bandgap using various reducing agents. It is found that sodium borohydride (NaBH4) can be a promising reducing agent, as it can reduce the bandgap to 2.30 eV and has a higher capacity to restore the carbon–carbon bonds compared with other reducing agents. Further bandgap tuning has been obtained by hydrogenation of GO as well as NaBH4-reduced GO (NGO). It was observed that after hydrogenation, the bandgap of GO was reduced from 2.48 to 1.95 eV, whereas it reduced from 2.45 to 1.87 eV in NGO. Hydrogenation of GO results in rearranging of C=O functionalities and removal of oxygen-containing groups. Furthermore, transmission electron microscopy observations corroborate the observation that after reduction with NaBH4, GO shows a more uniform nature than GO. The intensity ratio (I{1,100}/I{1,200}) of the {1,200} and {1,100} planes is found to be 1. After reduction with NaBH4, the ID/IG ratio decreased from 1.05 to 0.92, suggesting a decrease in defect density and better reduction. The intrinsic work function of GO and hydrogenated NGO is determined using electrostatic force microscopy and found to be 5.19 ± 0.1 eV and 4.39 ± 0.1 eV, respectively.