Amin K Qasim, Lawand L Mustafa, Adar Jamal Faris, Samir M Hamad
In this study, Ag ZnO nanocomposites were prepared by a plant mediated synthesis using an aqueous extract of Sumac (Rhus coriaria L.) seeds. The extract served as a source of phytochemical functional groups involved in metal ion complexation, reduction, and surface stabilization. The resulting material was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, UV visible spectroscopy, and Fourier transform infrared spectroscopy. SEM showed irregular aggregates with dimensions of approximately 50 to 200 nm, whereas XRD gave crystallite sizes of 13.85 to 44.51 nm, indicating that the larger SEM features can contain several smaller crystalline domains. The photocatalytic activity was evaluated using Congo red in aqueous solution under a 5 W LED source. Under the reported optimum conditions of 4 mg L-1 dye, pH 7, 35 °C, and 0.01 g catalyst per 20 mL solution, the degradation efficiency reached approximately 83% after 20 min. Scavenger experiments showed strong suppression of degradation in the presence of reactive species scavengers, supporting the participation of superoxide radicals, hydroxyl radicals, and photogenerated holes in the reaction pathway. The material retained 52.4% degradation efficiency after four reuse cycles. Antibacterial testing by the disk diffusion method showed concentration dependent inhibition, with Staphylococcus aureus giving the largest inhibition zones of 12 to 16 mm. These results indicate that the activity of the composite is more appropriately associated with interfacial charge transfer, reactive oxygen species generation, and defect related surface reactivity than with a large reduction in the intrinsic ZnO band gap. The study demonstrates the potential of an aqueous Sumac mediated route for preparing multifunctional Ag ZnO NCs for pollutant degradation and antibacterial applications.