Sol-Gel Derived Silver-Incorporated Titania Thin Films on Glass: Bactericidal and Photocatalytic Activity

Titanium dioxide (TiO2) and silver-containing TiO2 (Ag-TiO2) thin films were prepared on silica pre-coated float glass substrates by a sol-gel spin coating method. The bactericidal activity of the films was determined against Staphylococcus epidermidis under natural and ultraviolet (UV) illumination by four complementary methods; (1) the disk diffusion assay, (2) UV-induced bactericidal test, (3) qualitative Ag ion release in bacteria inoculated agar media and (4) surface topographical examination by laserscan profilometry. Photocatalytic activity of the films was measured through the degradation of stearic acid under UV, solar and visible light conditions. The chemical state and distribution of Ag nanoparticles, as well as the structure of the TiO2 matrix, and hence the bactericidal and photocatalytic activity, is controlled by post-coating calcination treatment (100-650 °C). Additionally, under any given illumination condition the Ag-incorporated films were found to have superior bactericidal and photocataltyic activity performance compared to TiO2 thin films. It is shown that with optimized thin film processing parameters, both TiO2 and Ag-TiO2 thin films calcined at 450 °C were bactericidal and photocatalytically active. © 2011 Springer Science+Business Media, LLC

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

Silver containing silica (Ag-SiO2) 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(OC2H5)(4)]/ethanol solution with aqueous silver nitrate (AgNO3) and aluminum nitrate nonahydrate [(AlNO3)(3)center dot 9H(2)O] solutions. The deposited films were calcined in air at 100, 300 and 500 A degrees 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-SiO2 films can be improved by Al addition. The Al-modified Ag-SiO2 thin films do not exhibit any coloring after calcination in the range of 100-500 A degrees 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-SiO2 thin films

Effect of silver incorporation on crystallization and microstructural properties of sol-gel derived titania thin films on glass

Titanium dioxide (TiO(2)) thin films, with and without silver (Ag), were prepared on float glass via sol-gel processing. The float glass substrates were pre-coated with a silica-barrier layer prior to the deposition of TiO(2)-based thin films. Silver nanoparticle incorporation into the TiO(2) matrix was achieved by thermal reduction of Ag ions dissolved in a titanium-n-butoxide (Ti[O(CH(2))(3)CH(3)](4)) based sol during calcination in air at 250, 450 and 650 A degrees C. Thin films were characterized using glancing incidence X-ray diffraction, UV-visible spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The effects of Ag concentration and calcination temperature on microstructure and on chemical and physical properties of the thin films have been reported. The size and chemical state of Ag particles, as well as the phase characteristics of the titania matrix were strongly influenced by Ag concentration and calcination temperature. Results from this study can be utilized in both processing and structure-functional property optimization of sol-gel based Ag-TiO(2) thin films by aqueous routes

Sol-gel derived silver-incorporated titania thin films on glass: bactericidal and photocatalytic activity

Titanium dioxide (TiO(2)) and silver-containing TiO(2) (Ag-TiO(2)) thin films were prepared on silica pre-coated float glass substrates by a sol-gel spin coating method. The bactericidal activity of the films was determined against Staphylococcus epidermidis under natural and ultraviolet (UV) illumination by four complementary methods; (1) the disk diffusion assay, (2) UV-induced bactericidal test, (3) qualitative Ag ion release in bacteria inoculated agar media and (4) surface topographical examination by laserscan profilometry. Photocatalytic activity of the films was measured through the degradation of stearic acid under UV, solar and visible light conditions. The chemical state and distribution of Ag nanoparticles, as well as the structure of the TiO(2) matrix, and hence the bactericidal and photocatalytic activity, is controlled by post-coating calcination treatment (100-650 A degrees C). Additionally, under any given illumination condition the Ag-incorporated films were found to have superior bactericidal and photocataltyic activity performance compared to TiO(2) thin films. It is shown that with optimized thin film processing parameters, both TiO(2) and Ag-TiO(2) thin films calcined at 450 A degrees C were bactericidal and photocatalytically active

Electrochemically driven degradation of chemical solution deposited ferroelectric thin-films in humid ambient

The ambient humidity significantly accelerates the degradation of lead zirconate titanate (PZT) films in microelectromechanical systems; the cause of such degradation is under debate. Here, it is shown that the degradation of chemical solution derived PZT thin-films in humid conditions is driven by the system's electrochemical activity toward water electrolysis. The layer stacks with Pt-based electrodes exhibited a faster degradation rate owing to their higher electrocatalytic activity compared to Au. A degradation model is proposed based on the electrolysis of liquid or gaseous H2O, involving the evolution of oxygen and hydrogen gas at the top and bottom electrodes. Degradation proceeds above the threshold voltage for a given electrode system and is driven by the evolution and pressure build-up of gaseous species at the PZT/electrode interfaces. The pressure build-up causes film cracking, delamination of the film and electrodes, electrothermal breakdown events, and eventually time-dependent dielectric breakdown. Significantly larger post-breakdown crater sizes in humid than in dry conditions suggests that larger cracks through which dielectric breakdown through humidified air can occur. Overall, these effects are shown to cause sample failure up to six orders of magnitude of time earlier than for operation in dry conditions. Thus, in order to improve the resilience of thin-film systems in humid conditions, it is imperative to protect the electrochemically active electrode components of the device. ACKNO

Electrochemically driven degradation of chemical solution deposited ferroelectric thin-films in humid ambient

The ambient humidity significantly accelerates the degradation of lead zirconate titanate (PZT) films in microelectromechanical systems; the cause of such degradation is under debate. Here, it is shown that the degradation of chemical solution derived PZT thin-films in humid conditions is driven by the system's electrochemical activity toward water electrolysis. The layer stacks with Pt-based electrodes exhibited a faster degradation rate owing to their higher electrocatalytic activity compared to Au. A degradation model is proposed based on the electrolysis of liquid or gaseous H2O, involving the evolution of oxygen and hydrogen gas at the top and bottom electrodes. Degradation proceeds above the threshold voltage for a given electrode system and is driven by the evolution and pressure build-up of gaseous species at the PZT/electrode interfaces. The pressure build-up causes film cracking, delamination of the film and electrodes, electrothermal breakdown events, and eventually time-dependent dielectric breakdown. Significantly larger post-breakdown crater sizes in humid than in dry conditions suggests that larger cracks through which dielectric breakdown through humidified air can occur. Overall, these effects are shown to cause sample failure up to six orders of magnitude of time earlier than for operation in dry conditions. Thus, in order to improve the resilience of thin-film systems in humid conditions, it is imperative to protect the electrochemically active electrode components of the device. ACKNOWacceptedVersio