Visible-Light-Induced Bactericidal Efficacy of a Platinium-Doped Titanium Photocatalyst

Abstract

TiO2 photocatalyst has been known to exhibit a notable disinfecting activity against a broad spectrum of microorganisms. Ultraviolet (UV) irradiation is damaging for human chronic contact to UV at the level to excite TiO2, which is photocarcinogenic. For this study photocatalyst possessing bactericidal activities that could reduce the bacterial population of all tested pathogens when illuminated by visible light was selected. We shifted irradiation wavelength of TiO2 nanoparticles (NPs) from far UV spectrum to visible (Vis) wavelengths by Platinum (Pt) doping. TiO2 and Pt-doped TiO2 (Pt/TiO2) NPs were synthesized via the sol-gel method in the form of powder and suspension, respectively. XRD, DRS, TEM and SEM techniques and EDX analysis were used to characterize the structure and properties of photocatalysts. Functional activity of both NPs was assessed in vitro by testing bactericidal activity against Escherichia coli and methicillin-resistant Staphylococcus aureus under UV and Visible irradiation. The results showed that the sizes of TiO2 and Pt/TiO2 nanoparticles were in the range of 20 to 50 nm with high crystallinity in the anatase phase. The minimum inhibitory concentration (MIC) of TiO2 and Pt/TiO2 NPs was found to be 0.125 mg mL-1. Interestingly, Pt-doping resulted in a marked shift in irradiation wavelength toward Vis spectrum with as almost the same growth inhibition efficacy as TiO2 at UV irradiation. TiO2 NPs reduced the growth rate of E. coli and S. aureus under UV irradiation for 24 hr by 94.3% ± 0.12 and 98% ± 0.16, respectively; while Pt/TiO2 NPs inhibited growth rate of aforesaid bacterial species at the same time period under Visible irradiation. After 24 hr, growth inhibitory action of Pt/TiO2 NPs on E. coli and S. aureus reached to 86% ± 0.11 and 90% ± 0.14, respectively. Taking together, we observed that visible-light responsive platinum-containing titania (Pt/TiO2) exerted high antibacterial property against pathogenic bacterial strains taken into consideration that apparent quantum efficiency for visible light-illuminated Pt/TiO2 is relatively higher than titania-based photocatalysts.