Synthesis of ZnO–TiO₂ Hybrid Nanoparticles via Plasma Jet Technique for Enhanced Photocatalytic and Antibacterial Applications

Abstract

ZnO, TiO₂, and ZnO–TiO₂ hybrid nanostructures were synthesized using an atmospheric-pressure plasma jet as a fast and solvent-free approach. Optical emission spectroscopy confirmed the formation of a stable oxygen plasma with an electron temperature of approximately 0.83 eV and an electron density of ~1.7 × 10¹⁷ cm⁻³. XRD analysis revealed well-defined crystalline phases with average crystallite sizes of about 12 nm for ZnO, 16 nm for TiO₂, and 14 nm for the ZnO–TiO₂ hybrid. Optical studies showed a significant band gap reduction to 2.68 eV for the hybrid compared with the individual oxides. The ZnO–TiO₂ hybrid exhibited superior photocatalytic activity toward methylene blue degradation under natural sunlight, achieving a degradation efficiency of 94.26% with a pseudo-first-order rate constant of 0.036 min⁻¹. Antibacterial evaluation demonstrated enhanced inhibition zone diameters of 29 mm against Staphylococcus aureus and 25 mm against Escherichia coli. The improved performance is attributed to efficient interfacial charge separation and enhanced reactive oxygen species generation at the ZnO–TiO₂ heterojunction.