Green Synthesis of Copper Nanoparticles Using <i>Stereum ostrea</i> Extract: Optimization, Structural Characterization, and Antimicrobial Activity

ABSTRACT The green synthesis of copper nanoparticles (Cu NPs) using mushroom biomass is an eco‐friendly and sustainable alternative to conventional chemical and physical methods. The bioactive compounds in the mushroom biomass act as reducing and stabilizing agents, facilitating the nanoparticle synthesis without the need for toxic reagents. This study explores the biosynthesis of Cu NPs, an aqueous mushroom extract from S . ostrea . The development of a dark ocher color confirmed the formation of SO‐Cu (II) NPs. Various parameters were optimized, including concentration of CuSO 4 .5H 2 O, extract level, and procurement period to achieve enhanced nanoparticle yield. The optimal concentration of CuSO 4 .5H 2 O was 1 M, the optimal extract level was 1%, while the procurement period determined was 45 min. The synthesized Cu NPs were characterized using UV–vis spectroscopy, FTIR, XRD, and SEM. UV–vis spectroscopy showed a distinct surface plasmon resonance (SPR) peak in the range of ∼290 nm. SEM showed the structure, FTIR revealed distinct functional groups, and the crystalline nature of myco‐synthesized Cu NPs was confirmed by XRD analysis. Concentration‐dependent antimicrobial activity was observed, as 10 µL produced better results than 5 µL. This mushroom‐mediated synthesis approach aligns with green chemistry principles, offering a low‐cost, nontoxic, and scalable method with promising implications in medicine.