Influence of Mg doping on the structural, morphological, optical, thermal, and visible-light responsive antibacterial properties of ZnO nanoparticles synthesized via co-precipitation.

Mg-doped zinc oxide (Zn1-xMgxO, where x = 0.000, 0.001, 0.003, 0.005, and 0.010 M) nanoparticles (MgZnO NPs) were synthesized via a co-precipitation method and subjected to various analyses for application as functional additives in food packaging. The MgZnO NPs were successfully formed at approximately 360 °C and showed an increase in the optical band gap with respect to the increase in the concentration of Mg doping. The X-ray diffraction and scanning electron microscopy analyses of MgZnO NPs confirmed the formation of hexagonal wurtzite structure and rod-like morphology. X-ray photoelectron spectra revealed that the Mg (1s) peaks centered at 1303.35 and 1303.38 eV were ascribed to the presence of Mg2+ replacing Zn2+. Transmission electron microscopy images showed rod shapes with the length of 208-650nm and width of 84-142 nm. Various concentrations of synthesized MgZnO NPs were investigated against a gram-negative (Escherichia coli - DH5α) bacterial strain under light and dark conditions. Among the studied samples, 0.010 M MgZnO NPs of concentration 3 mg/mL showed the best antibacterial activity under the light condition. MgZnO NPs revealed uneven ridges on the outer surface, which promote the diffusion ability of Zn2+ and increased production of reactive oxygen species, and consequently lead to bacterial lysis. Furthermore, this study demonstrates excellent feasibility for the application of MgZnO NPs as fillers with good antibacterial activity, especially in antimicrobial food packaging applications.