Antimicrobial Activity of Zinc Oxide–Graphene Quantum Dot Nanocomposites: Enhanced Adsorption on Bacterial Cells by Cationic Capping Polymers

Abstract

Development of low-cost, high-performance antibacterial reagents is of critical importance in the face of increasing occurrence of bacterial resistance against conventional antibiotics. In the present study, polyethylenimine (PEI)-modified graphene quantum dot (GQD) and ZnO nanoparticle nanocomposites, which were readily dispersed in water and exhibited markedly enhanced antimicrobial activity toward Escherichia coli, as compared to the PEI-free ZnO/GQD counterparts, were prepared by a facile sol–gel method. This was largely ascribed to the reduced size of the nanoparticles and the enhanced adsorption of the nanocomposites onto the bacterial cell surfaces, as manifested by adsorption experiments and TEM characterization of the bacterial cells, as well as electron spin resonance measurements. The results highlight the significance of structural engineering of functional nanocomposites in the development of efficient antibacterial agents.