Enhanced Photocatalytic and Antimicrobial Activity of Cr-Doped Co3O4 Nanoparticles under Natural Sunlight

In this work, pristine and chromium (Cr)-substituted cobalt oxide (Co3O4) nanoparticles were successfully synthesized using a co-precipitation approach. A comprehensive investigation was carried out to evaluate the influence of Cr incorporation on the structural, morphological, surface area, optical behavior, photocatalytic efficiency, and antimicrobial performance. X-ray diffraction confirmed the formation of a cubic spinel structure, with Cr doping inducing lattice modifications due to ionic substitution. SEM examination revealed the irregular spherical morphology of the synthesized MNPs and EDX analysis confirmed the elemental composition. BET analysis indicates the 5% Cr doped Co3O4 NPs exhibited the higher surface area with lower pore volume and diameter. UV-Vis DRS showed enhanced optical absorption and a tunable band gap (2.85-3.1 eV) with Cr doping. FTIR analysis identified functional groups, while photoluminescence spectra revealed reduced emission intensity, suggesting lower recombination rates of charge carriers. Dielectric studies indicated increased polarizability and optical conductivity with Cr incorporation. The photocatalytic efficacy was assessed by the breakdown of MB dye under sunlight, where 5% Cr-doped Co3O4 showed the highest degradation efficiency (96%) and rate constants, demonstrating superior photocatalytic activity. Antibacterial testing against Escherichia coli and Pseudomonas aeruginosa and antifungal testing against Aspergillus niger and Candida albicans revealed improved antimicrobial efficacy with Cr doping. The doping of Cr into Co3O4 NPs enhances their photocatalytic activity toward MB dye degradation under sunlight, while Cr incorporation also inhibits microbial growth, making them more suitable for photocatalytic and antimicrobial applications.