Investigation of physical and antibacterial characteristics of ZnCo2O4 semiconductor films

A ZnCo2O4 film is prepared using the sol–gel method. The sample is subjected to heat treatment under nitrogen at 200–600 °C. When the sample is annealed at 200 °C, it exhibits an amorphous Zn–Co–O film with low surface roughness, high light transmittance, and no conductivity. When the sample is annealed at 250 °C, a spinel ZnCo2O4 film is formed. With a gradual increase in temperature to 600 °C, the degree of crystal order, crystal size, surface polygonal structure, and root mean square roughness of the ZnCo2O4 film increase. The transmittances of the spinel ZnCo2O4 are 58.98–43.68% at a wavelength of 550 nm, which indicate a translucent characteristic. For the films annealed at 300 and 350 °C, the film resistivities are 8.22 and 24.26 Ω cm, respectively, and the corresponding carrier concentrations are 2.98 × 1018 and 2.48 × 1018 cm−3. The ZnCo2O4 film is a p-type semiconductor. The ZnCo2O4 film exhibits high antibacterial properties against both Escherichia coli and Staphylococcus aureus under bright and dark conditions (no photocatalysis), with antibacterial rates of 99.86% to 99.99%. Therefore, ZnCo2O4 demonstrates immense potential for antibacterial and optoelectronic applications.