Biocidal properties of TiO₂ powder modified with Ag nanoparticles

Silver nanoparticles (NPs) were synthesized sonochemically by the reduction of silver ions with ethylene glycol and simultaneously deposited on different forms of TiO₂ powders (commercial Degussa P-25, synthetic anatase and mesoporous titania). The Ag-TiO₂ nanocomposites were characterized by X-ray electron diffraction (XRD), transmission electron microscopy (TEM), energy-dispersed X-ray analysis (EDX), UV absorption spectroscopy (UV), Z-potential measurements and electron paramagnetic resonance (EPR). The results demonstrated homogeneous distribution of silver nanoparticles ∼3 nm in size, strongly attached to the surface of titania. The antimicrobial properties of Ag-TiO₂ were tested against a number of Gram-positive and Gram-negative bacteria. A high bactericidal effect was found in the absence of UV light. The reduction in bacterial viability was between 3 and 4.2 logs. Based on the experimental data it was concluded that enhanced antimicrobial activity of the Ag-TiO₂ originated from both the oxidative stress generated by silver nanoparticles and the presence of silver ions on the surface of the silver-titania composite.