Green Synthesis of l-Cysteine-Functionalized rGO-Silver Nanoparticles for Enhanced Photocatalytic and Antibacterial Applications

Abstract

In this study, we developed an eco-friendly two-step synthesis of an l-cysteine/reduced graphene oxide-silver nanoparticle (l-Cys-rGO-AgNPs) hybrid material using l-cysteine and l-ascorbic acid as reducing agents. The successful formation and uniform distribution of AgNPs (20–40 nm) on rGO sheets were confirmed by FTIR, XRD, FESEM, and EDX analyses. The nanocomposite achieved 71% photocatalytic degradation of methylene blue and demonstrated potent antibacterial properties against Escherichia coli, with over 99.9% reduction, and weaker performance against Staphylococcus aureus, producing 30–70% reduction. FESEM imaging demonstrated substantial damage to bacterial membranes, with E. coli showing the most disruption, which proves stronger antibacterial effects. These results show that l-Cys-rGO-AgNPs can act as a multifunctional material supporting sustainable environmental remediation and antimicrobial uses.