Antimicrobial activity of printed composite TiO2/SiO2 and TiO2/SiO2/Au thin films under UVA-LED and natural solar radiation

Composite TiO2/SiO2 porous coatings modified with bipyramid-like gold nanoparticles were prepared by means of sol-gel and inkjet printing technique, comprehensively characterized and studied for photocatalytic disinfection of drinking water with fecal contamination by natural bacteria consortia. Photocatalytic antimicrobial activity of prepared thin films was evaluated against gram-negative (Escherichia coli and Total coliforms) and gram-positive bacteria (Enterococci). Elimination rate of all tested bacteria increased when photocatalytic coatings were used in comparison with solar disinfection. The best results in terms of antimicrobial activity were obtained with TiO2/SiO2/Au thin films under natural solar radiation, which demonstrated the highest antimicrobial activity, enhancing the inactivation rates of E. coli, Total coliforms and Enterococci 1.5, 1.3 and 1.6 times, respectively as compared to solar disinfection without photocatalyst. Remarkable difference in bacteria sensitivity for photocatalytic disinfection was observed with trend E. coli > Total coliforms > Enterococci. No release of gold and titanium was detected during photocatalytic water disinfection test. Regrowth of E. coli, Total coliforms and Enterococci after photocatalytic bacteria inactivation under UVA-LED and natural solar radiation was lower than 1% (24, 48 and 72 h), indicating potential application of prepared coatings for production of safe drinking water.