Green synthesis of ZnO/CQD nanocomposite using chestnut shell and evaluating its photocatalytic antimicrobial activity under visible light

This research evaluated the photocatalytic antimicrobial activity under visible light and investigated its mechanisms by synthesizing CQDs and ZnO from a single ingredient, chestnut shells, a food processing byproduct, and then wrapping CQDs on the ZnO to form a nanocomposite. Characterization confirmed successful synthesis, highlighting the potential to economically and sustainably produce two nanomaterials from one source. When CQDs were wrapped onto ZnO at an 8% ratio (8%-ZnO/CQD), the highest photocatalytic antimicrobial activity was achieved. The study demonstrated that CQDs effectively suppress the recombination of photoexcited electron-hole pairs, increasing the generation of reactive species, such as e⁻ and •OH. The increased surface area from CQD wrapping led to the production of intracellular reactive oxygen species (iROS), further enhancing their antimicrobial activity and causing cell membrane damage. These findings suggest that 8%-ZnO/CQD holds promise for microbial control, offering a cost-effective and environmentally friendly solution to reducing water- and food-borne diseases.