Green Synthesis of Copper-Based Nanomaterials Using Pleurotus ostreatus: Process Optimization and Multi-technique Characterization

Green synthesis provides a biological route for preparing copper-based materials. This study assessed reaction conditions for producing copper-based nanomaterials from fresh Pleurotus ostreatus fruiting-body extract and characterised the recovered material using complementary physicochemical techniques. A one-factor-at-a-time approach examined extract concentration, reaction pH, temperature and duration. Visual changes and UV–visible absorption were used to select conditions for subsequent preparation. An extract concentration of 15% (w/v), 5 mM CuSO₄, pH 8.5, 70 °C and 180 min were selected on the basis of optical response and physical appearance. UV–visible spectra showed a prominent absorption feature at 200–220 nm, together with secondary features that varied across reaction conditions. X-ray diffraction produced a broad pattern without clearly resolved characteristic peaks attributable to crystalline copper phases. Fourier-transform infrared spectra showed bands at 3242.87, 1606.93, 1025.42 and 611.85 cm⁻¹, indicating functional groups potentially associated with mushroom-derived biomolecules. Field-emission scanning electron microscopy showed irregular, aggregated nanoscale particles with a reported mean size of 38.7 nm. Energy-dispersive X-ray spectroscopy detected copper (3.6 wt%) alongside substantial carbon, nitrogen and oxygen signals. The measured zeta potential (−7.2 ± 2.1 mV) suggested limited electrostatic stabilisation. These findings provide a preliminary synthesis protocol and characterise a copper-containing material associated with organic constituents of the mushroom extract, while leaving its copper phase and oxidation state unresolved.