Effect of annealing temperature on the morphology and antibacterial activity of Mg-doped zinc oxide nanorods

Herein, magnesium-doped zinc oxide nanorods (MgZnO NRs) were synthesized by the co-precipitation method and annealed at different temperatures in the range of 100–500 °C. The increase in the annealing temperature was found to influence both chemical and morphological structures of the MgZnO NRs: Ultraviolet–visible diffuse reflectance spectroscopy showed an increase in band gap with increase in the annealing temperature. Fourier-transform infrared spectra showed that two characteristic peaks at 487 cm⁻¹ and 442 cm⁻¹ corresponding to a weak Zn–O stretching initially decreased and then disappeared with increase in the annealing temperature. Moreover, the MgZnO NRs annealed at 100 °C had large crystallite size, high aspect ratio, and narrow edges. Remarkably, the MgZnO NRs annealed at 100 °C exhibited the highest antibacterial activity against both S. aureus and E. coli strains, attributed to the high aspect ratio and diffusion ability of the Zn²⁺ ions and large surface charge, crystallite size, and surface area. The MgZnO NRs annealed at the relatively low temperature of 100 °C could be easily produced commercially, in large quantities, and effectively used to prevent the growth of foodborne microbes in food packaging applications.