Investigating functional groups in GO and r-GO through spectroscopic tools and effect on optical properties

Recently, graphene oxide (GO) has gained more attention because of its various physicochemical properties, which can be tailored by optimizing the functional groups present at the edges of carbon atoms. The current research work reports on the synthesis of GO by modified Hummers method and its thermal reduction. Go is stable after 187 °C as revealed in TG-DTA analysis; therefore, it was reduced at 300 °C. After reduction, the interlayer spacing decreases from 0.92 to 0.30 nm with increase in sp2 and sp3 carbon atoms as observed in XRD and XPS, respectively. The presence of functional groups has been investigated by spectroscopic tools. R-GO is few-layer graphene sheets as revealed in Raman spectroscopy. Also, separate and enhanced wrinkle sheets are observed in FESEM image. The effect of electron concentration, structural ordering, and restoration of sp2 carbon atoms on the optical properties are investigated by photoluminescence (PL) and ultraviolet-visible (UV) spectra.