Green reduction of graphene oxide using Bacillus sphaericus

Abstract

While chemical methods are often used to convert graphene oxide (GO) to reduced graphene oxide (RGO), chemical reduction is often environmentally unfriendly due to the high toxicity of many chemical reducing agents. To address this limitation, Bacillus sphaericus was used here for the green reduction of GO to RGO. Successful reduction was confirmed by various advanced characterization techniques including Ultraviolet–Visible (UV–vis), X-ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM-EDS). With a new peak attributable to RGO at 261 nm appearing in UV–vis and XRD spectra of the reduced product also developed a new peak at 2θ = 24.6° characteristic of RGO. Successful reduction was also supported by Raman spectroscopy which showed that the ratio of the intensity band (D band: G band) increased from 0.99 to 1.17. FTIR and XPS both confirmed that specific OH (3399 cm−1), CO (1734 cm−1) and COC (287 eV) bonds were reduced. Cyclic voltammograms (CVs) showed that the produced RGO exhibited good conductivity (changed from 0.8 to 1.1 mW·cm−2). This work developed a green and easy operated method of synthesizing RGO using microorganisms.