Antibacterial mechanism of phyto-synthesized CuO-decorated ZnO nanostructure in relation to hydrogen peroxide generation under visible-light condition

In this study, CuO-decorated ZnO (ZC) heterojunction nanocomposite was successfully green synthesized as a light-enhanced antibacterial material using Muntingia calabura leaf extract. Resultantly, it showed the formation of rice grain-shaped particles with 100 − 250 nm in length and 50 − 100 nm in width as shown through field emission-scanning electron microscopy images. Subsequently, the antibacterial activity of the ZC was evaluated against both Gram-negative and Gram-positive strains, in which the bactericidal properties of the material significantly increased upon being illuminated. The band structure of ZC nanocomposite reveals that the material generates free radicals and releases Zn2+ and Cu2+ ions to initiate the destruction of cell membranes. Besides, the ZC can also absorb light in the visible spectrum with a bandgap energy of 2.94 eV along with a feasible band structure that can facilitate the generation of free radicals as well as H2O2 concentration of 25 µM through a generation experiment within an oxygen-aerated aqueous media. Conclusively, the obtained results imply the great antibacterial capability for medical applications of green synthesized nanomaterials using biological plant extracts. Moreover, such results open up a new pathway to produce heterostructure through the use of plant extracts.