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

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 <i>Escherichia coli</i>, with over 99.9% reduction, and weaker performance against <i>Staphylococcus aureus</i>, producing 30-70% reduction. FESEM imaging demonstrated substantial damage to bacterial membranes, with <i>E. coli</i> 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.