Effect of CuO on the Structural, Antimicrobial, and Redox Activity of TiO2/TeO2/CuO Sol–Gel Powders

This study investigates the synthesis, characterization, antimicrobial performance, and redox activity of sol-gel-derived TiO₂/TeO₂/CuO powders. The as-prepared gel with the nominal composition 80TiO₂/10TeO₂/10CuO was subjected to thermal treatment at 400 °C and 600 °C for 2 h, resulting in the formation of composite materials at both temperatures. By UV-Vis spectroscopy, it has been found that CuO is responsible for the red shifting of the absorption edge. The SEM-EDS analysis verified the elemental composition of the synthesized powders. The antimicrobial activity of the heat-treated powders was proved against <i>Escherichia coli</i> ATCC 25922 and <i>Staphylococcus aureus</i> ATCC 25923, representative Gram-negative and Gram-positive bacteria frequently associated with hospital-acquired infections and antibiotic resistance. At physiological pH, the 600 °C-treated sample exhibited strong prooxidant properties, supporting antimicrobial activity. At alkaline conditions, the nanomaterials were effective against superoxide radicals. The variation in oxidation with changes in pH is indicative of the potential for controlled application. Antimicrobial activity was assessed through minimum inhibitory concentration (MIC) assays and spot and luminescent tests, providing both quantitative and qualitative evaluations.