Preparation and antibacterial properties of laser-generated silver-anatase nanocomposite film against Escherichia coli and Staphylococcus aureus

Anatase-based titanium dioxide (TiO2) naturally possesses a well recognized antibacterial effect under ultraviolet excitation. However, anatase modified with silver nanoparticles (Ag NPs) exhibits even stronger antibacterial action in natural daylight. The purpose of our present research is to evaluate the photocatalytic antibacterial effects of laser-generated silver-anatase nanocomposite film against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). A sol-gel TiO2 precursor was spin-coated on a clean glass slide and silver ions were self-adsorbed from aqueous solution. A pulsed beam of KrF excimer laser (248 nm, 13 ns) was traversed over the amorphous film, leading to the crystallization of the anatase and formation of cubic as well as hexagonal Ag NPs. A scanning transmission electron microscope analysis revealed a 30-40 nm anatase crystallite size, whereas an average size of 9.6 nm was obtained from Ag NPs. The photo-absorption of plain anatase was red-shifted to 516 nm with the addition of Ag NPs after the laser treatment. Moreover, no colonies of E. coli and S. aureus cells were observed to survive after 60 min of contact with the laser-modified silver-anatase films in the dark and in daylight conditions.