Green synthesis, characterization, and antimicrobial applications of bismuth nanoparticle–chitosan composites

The integration of nanomaterials with green chemistry has emerged as a rapidly growing and safe approach, replacing conventional, toxic synthesis methods and establishing new standards across scientific research. In the present work, novel bismuth nanoparticles (BiNPs) were synthesized using a green route, employing the leaf extract of Eucalyptus camaldulensis as both a reducing and stabilizing agent, followed by the formation of bismuth nanoparticle–chitosan (BiNPs–CS) composites. UV-Vis, FTIR, and XRD spectroscopic techniques were employed to confirm the biosynthesis of BiNPs and BiNPs-CS, as well as the interaction between BiNPs and chitosan. Both XRD and direct size measurement using dynamic light scattering (DLS) confirmed that the average size of the nanoparticles in the composites remained approximately 15 nm. Based on the recovered dried product from synthesis repeated in triplicate, the average yield of synthesized BiNPs-CS was found to be 79% with a standard deviation of 1.7%, and the reaction exhibited an overall good reproducibility. Antimicrobial activity of the designed BiNPs–CS composites was evaluated against methicillin-resistant Staphylococcus aureus (MRSA) using the well diffusion method, which reflected their strong antimicrobial potential as inhibition zones of up to 17 mm were recorded with a 40 µg/mL BiNPs–CS composites solution. These findings delineated a simple, eco-friendly mechanism for the synthesis of metal-based nanocomposites with potential biomedical applications.