COMPARATIVE ANTIMICROBIAL AND PHOTOCATALYTIC PERFORMANCE OF MG-DOPED ZNO, NIO, AND COO NANOPARTICLES AGAINST ORGANIC DYES AND PATHOGENS

Abstract

Metal oxide nanoparticles have attracted considerable attention because of their potential applications in environmental remediation and antimicrobial technologies. The present study comparatively evaluated the antimicrobial and photocatalytic properties of Mg-ZnO, Mg-NiO and Mg-CoO nanoparticles. The antimicrobial activity was investigated against selected Gram-positive and Gram-negative bacteria and fungal strains using the disc diffusion method. Among the tested nanoparticles, Mg-CoO exhibited the strongest antibacterial activity, producing maximum inhibition zones of 22 mm against Bacillus cereus and 20 mm against Staphylococcus aureus. Mg-CoO showed a minimum inhibitory concentration (MIC) of 420 µg/mL and a minimum bactericidal concentration (MBC) of 460 µg/mL against S. aureus. Mg-ZnO showed comparatively broader antimicrobial activity, with the highest inhibition zone of 18 mm against Escherichia coli. In contrast, Mg-NiO demonstrated relatively weak antimicrobial activity under the tested conditions. The photocatalytic performance of the nanoparticles was evaluated for the degradation of methylene blue (MB) and Congo red (CR) under UV irradiation at 365 nm. Mg-ZnO demonstrated the highest photocatalytic efficiency, achieving 95.0% degradation of MB and 87.3% degradation of CR after 300 min of irradiation. Mg-NiO exhibited comparable activity toward MB, with 92.5% degradation, whereas Mg-CoO showed only 6.7% MB degradation under identical conditions. Apparent pseudo-first-order kinetic analysis further supported the superior photocatalytic activity of Mg-ZnO, with rate constants of 0.01009 min⁻¹ for MB and 0.00691 min⁻¹ for CR, compared with 0.00874 min⁻¹ for Mg-NiO toward MB. Overall, the findings demonstrate pronounced composition-dependent functional properties among the investigated nanoparticles, with Mg-CoO showing greater antibacterial potential and Mg-ZnO exhibiting superior photocatalytic performance. These findings highlight the potential of Mg-based metal oxide nanoparticles for application-specific antimicrobial and environmental remediation purposes.