Abstract
Titania (TiO2) induced photocatalysis has been widely investigated and applied as a disinfection strategy in many industrial and clinical applications. Reactive oxygen species (ROS), including hydroxyl radicals (&8226OH), superoxide radicals () and hydrogen peroxide (H2O2), generated in the photocatalytic reaction process are considered to be the active components prompting the bactericidal effect. In the present work, the kinetics of photocatalytic inactivation of Staphylococcus epidermidis and specific contributions of •OH, and H2O2 to the bactericidal process were studied using two disinfection settings sutilizing photocatalytic resin-TiO2 nanocomposite surfaces and suspended TiO2 nanoparticles, respectively. In antibacterial tests against S. epidermidis with a layer of bacterial suspension on the resin-TiO2 surfaces, H2O2 was found to be the most efficient ROS component contributing to the antibacterial effect. Disinfection kinetics showed a two-step behavior with an initial region having a lower disinfection rate followed by a higher rate region after 10 min of UV irradiation. By contrast, in antibacterial tests with suspended bacteria and photocatalytic TiO2 nanoparticles, •OH and H2O2 showed equal significance in the bacterial inactivation having a typical Chick-Watson disinfection kinetics behavior with a steady disinfection rate. The results contribute to the understanding of the bactericidal mechanism and kinetics of photocatalytic disinfection that are essential for designing specific antibacterial applications of photocatalytic materials.
Highlights
Since Matsunaga et al demonstrated the biocidal effect of TiO2 under metal halide lamp irradiation in 1985 [1], there has been an increasing interest in the application of the photocatalytic reaction of TiO2 as an alternative disinfection strategy to traditional chemical methods or antibiotics [2] [3]
Disinfection kinetics showed a two-step behavior with an initial region having a lower disinfection rate followed by a higher rate region after 10 min of UV irradiation
The results showed that for all three scavengers, increasing the concentration above 1 mg/ml did not appreciably increase its capability to block the antibacterial effect of the photocatalytic process
Summary
Since Matsunaga et al demonstrated the biocidal effect of TiO2 under metal halide lamp irradiation in 1985 [1], there has been an increasing interest in the application of the photocatalytic reaction of TiO2 as an alternative disinfection strategy to traditional chemical methods (e.g. alcohols, aldehydes, iodine, phenols and chlorine) or antibiotics [2] [3]. The mechanism of TiO2 induced photocatalysis involves the excitation of electrons from the valence band of this semiconductor to the conductive band through the absorption of light with sufficient energy (wavelength about 385 nm or less, depending on the size of the band gap). This results in the formation of electron-hole pairs with strong reducing and oxidizing potentials: TiO2 + hv → e−CB + h+VB (1). TiIV sites in the titania crystals can trap the conduction band electrons and be reduced to TiIII sites, which can in turn react with the O2 adsorbed at TiIII sites and generate superoxide (Equations (4) and (5)).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
