Fungal-Mediated Green Synthesis of ZnO-NPs: Characterization and Sonocatalytic Activity

An eco-friendly biogenic approach for the synthesis of zinc oxide nanoparticles using a mushroom extract as a capping agent is reported in this study. Comprehensive characterization was performed by comparing as-prepared mushroom-coated nanoparticles (ZnO–BC) with calcined pure nanoparticles (ZnO–AC at 450 °C) by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), dynamic light scattering (DLS), Zeta potential, thermal gravimetric analysis (TGA), and X-ray diffraction (XRD). According to AFM and DLS results, the 10–15 nm cores were dispersed in the organic matrix for the ZnO–BC sample, while these cores converted into well–defined, clean hexagonal ZnO nanograins (10–40 nm) for ZnO–AC. The Zeta potential values changed from −16 mV for ZnO–BC to +24 mV for ZnO–AC, indicating that the negatively charged biomolecular capping groups were removed, yielding an uncapped ZnO surface. The investigation of ZnO–AC as a heterogeneous sonocatalyst in the Claisen–Schmidt condensation under ultrasonic irradiation afforded the corresponding chalcones in 90–98% yields within 4–11 min at 50 °C in EtOH/H2O. Hot filtration test confirmed no detectable zinc leaching under the experimental conditions, and the catalyst remained robustly stable over five cycles with favorable green metrics (AE = 90.2% and E-factor = 0.18).