Highly efficient and morphology dependent antibacterial activities of photocatalytic Cu_xO/ZnO nanocomposites

This study reports on morphology dependent antibacterial activities of Cu_xO/ZnO nanocomposites towards Escherichia coli. The Cu_xO/ZnO nanocomposites were formed by aqueous photoreduction of Cu_xO nanostructures on solution grown ZnO nanorods on Si substrates. By controlling the photoreduction time and temperature, various Cu_xO nanostructures including nanocubes, nanoclusters, nanospikes, and nanowebs were created as verified by scanning electron microscopy. X-ray diffraction analysis reveals the good crystallinity of the ZnO nanorods. X-ray photoelectron spectroscopy confirms the successful deposition of CuO and Cu₂O nanostructures on the nanorods. Antibacterial tests were performed in dark and under low-intensity blue-light irradiation. The nanoweb sample has an antibacterial efficiency of 95.8% for 10 min in dark and the nanospike sample has an efficiency of 99.5% for 10 min under light. For the nanospike sample, remarkable bacterial survival ratios of 3 × 10^–4 and 10^–5 in dark and under light both for a 60 min reaction time, respectively, have been achieved. The excellent antibacterial performance is attributed to combined effects of mechanical piercing of ZnO nanorods, release of Zn²⁺, Cu²⁺, and Cu⁺ ions, and effective generation of reactive oxygen species due to charge separation.