Synthesis And Physicochemical Characterization Of Graphene Oxide–Gold Nanoparticle (Go–Aunp) And Reduced Graphene Oxide–Gold Nanoparticle (Rgo–Aunp) Composites With Preserved Plasmonic Integrity For Potential Radiosensitization Applications

Abstract

Graphene-based nanomaterials and gold nanoparticles (AuNPs) are nanomaterials whose optical and electronic properties have increasingly drawn interest in the biomedical field. In this research, AuNPs were prepared using two chemical synthesis processes, i.e., the Turkevich sodium tri-citrate reduction technique and the ascorbic acid reduction method, and combined with graphene oxide (GO) and reduced graphene oxide (RGO) to generate four nanocomposites. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to perform structural characterization. UV-Visible spectroscopy and Raman spectroscopy were used to determine optical properties, and TGA and differential scanning calorimetry (DSC) were performed on GO. In all four composite formulations, the localized surface plasmon resonance (LSPR) peak was retained at approximately 525–537 nm, consistent with well-dispersed, non-aggregated AuNPs in the 20–40 nm size range. The preservation of the LSPR peak position across all formulations, independent of reducing agent identity (sodium tri-citrate vs. ascorbic acid) and graphene matrix type (GO vs. RGO), confirms successful non-aggregated AuNP decoration of the graphene sheets. RGO–AuNP composites exhibited substantially higher absorbance across the visible spectrum relative to GO–AuNP composites, attributable to the restored sp² conjugation of the RGO lattice. XRD confirmed the successful synthesis of GO and RGO. SEM revealed characteristic sheet morphologies consistent with Hummers-derived GO and ascorbic acid-reduced RGO. Raman spectroscopy of RGO–AuNP composites confirmed D- and G-band features consistent with defect-rich graphene lattices. TGA confirmed GO thermal stability up to 215 °C, well above physiological temperature. These results establish GO–AuNP and RGO–AuNP composites as structurally and optically well-characterised platforms for potential radiosensitization applications, with the AuNP plasmonic response preserved upon graphene functionalisation.