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 similar to 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.