A Facile and Green Approach for the Preparation of Silver Nanoparticles on Graphene Oxide with Favorable Antibacterial Activity

Herein, we introduce a simple precipitation method for preparing graphene oxide-silver nanoparticle (GO/AgNP) composites, utilizing Calendula officinalis (C. officinalis) seed extract as both a reducing and stabilizing agent. Our research combines the sustainable preparation of graphene oxide (GO) with the green synthesis of silver nanoparticles (AgNPs), aiming to explore the potential of the obtained composite as a novel antibacterial material. To establish a benchmark, the synthesis was also performed using sodium citrate, a conventional reducing agent. The resultant GO/AgNP composites were characterized through several analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, X-ray diffraction (XRD), infrared (IR) spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy, confirming the successful functionalization of GO with AgNPs. The antibacterial effectiveness of the composites was systematically assessed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with nanoparticle concentrations spanning from 0 to 250 µg/mL, utilizing mostly disk diffusion and colony-forming unit (CFU) count assays. The AgNPs were characterized by a size range of 15-50 nm. Notably, the GO/AgNP composite prepared using C. officinalis seed extract demonstrated superior antibacterial activity at all tested concentrations, outperforming both pure GO and the GO/AgNP composite prepared with sodium citrate. The most pronounced antibacterial effect was observed at a concentration of 32.0 µg/mL. Therefore, this innovative synthesis approach may offer a valuable contribution to the development of new therapeutic agents to combat bacterial infections, suggesting further exploration into antibacterial coatings or potential drug development.