Silver containing sol–gel derived silica thin films: effect of aluminum incorporation on optical, microstructural and bactericidal properties

Silver containing silica (Ag–SiO 2 ) thin films with and without aluminum (Al) were prepared on soda-lime-silica glass by spin coating of aqueous sols. The coating sol was formed through mixing tetraethyl orthosilicate [Si(OC 2 H 5 ) 4 ]/ethanol solution with aqueous silver nitrate (AgNO 3 ) and aluminum nitrate nonahydrate [(AlNO 3 ) 3 ·9H 2 O] solutions. The deposited films were calcined in air at 100, 300 and 500 °C for 2 h and characterized using x-ray diffraction, UV-visible and x-ray photoelectron spectroscopy. The effect of Al incorporation and calcination treatment on microstructure and durability of the films, and chemical/physical state of silver in the silica thin film have been reported. The bactericidal activity of the films was also determined against Staphylococcus aureus via disk diffusion assay studies before and after chemical durability tests. The investigations revealed that the optical, bactericidal properties and chemical durability of Ag–SiO 2 films can be improved by Al addition. The Al-modified Ag–SiO 2 thin films do not exhibit any coloring after calcination in the range of 100–500 °C, illustrating that silver is incorporated within the silica gel network in ionic form (Ag + ). Al incorporation also improved the overall durability and antibacterial endurance of Ag–SiO 2 thin films.