Effective Photogeneration of Singlet Oxygen and High Photocatalytic and Antibacterial Activities of Porous Mn-Doped ZnO-ZrO₂ Nanocomposites

Disperse porous Mn-doped ZnO-ZrO₂ nanocomposites were prepared using the facile polymer-salt method. The effect of Mn content on the crystal structure, composite morphologies, their ability to photogenate the singlet oxygen, luminescence properties, and bactericidal activities were studied. The crystal structure and morphology of these materials were investigated using XRD and SEM analysis. It was found that obtained nanocomposites consist of small (~9 nm) hexagonal ZnO and fine ZrO₂ crystals and the embedding of Mn ions expands the crystal cells of ZnO crystals. Photoluminescence spectra indicate the presence of different structural defects (interstitial Zn ions and oxygen vacancies in ZnO and oxygen vacancies in ZrO₂ crystals). Mn-doped ZnO-ZrO₂ nanocomposites can photogenerate singlet oxygen under visible (λ = 405 nm) irradiation. The increased power density of the exciting blue (λ = 405 nm) light significantly enhances the singlet oxygen photogeneration by prepared composites. The dependence of the intensity of singlet oxygen photogeneration by composites on the power density of exciting radiation (at its variation in the range 0.8 ÷ 1.6 W/cm²) is close to linear. Mn-doped ZnO-ZrO₂ composites demonstrate superior antibacterial activity against the gram-positive bacteria Staphylococcus aureus ATCC 209P. It was found that highly dispersed porous Mn-doped ZnO-ZrO₂ nanocomposites are promising for practical environmental and medical applications.