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Antimicrobial properties of TiO2-SiO2 thin films

Erdural, B. Korkmaz
Karakaş, Gürkan
Bakir, U.
Suludere, D.
Titanium dioxide (TiO2) is one of the most important and most widely used semiconductor photocatalyst due to its application in solar energy conversion and environmental purifications. In this study, SiO2 used as support material and deposition of TiO2 films on glass surfaces by using a SiO2–TiO2 binary system has been performed. The SiO2 supported TiO2 samples were synthesized by sol–gel technique by using SiO2 colloidal solution and hydrolysis of TTIP. The thin films over soda glass plates were obtained by dip coating followed by calcination at 500°C. The photocatalytic activities of the samples were measured with methylene blue stain degradation and antimicrobial effect against Escherichia coli under artificial sunlight. It was found that the antimicrobial activity is enhanced by the increasing ratio of SiO2/TiO2. By contrast, the methylene blue degradation is suppressed on the surfaces with higher SiO2/TiO2 ratio in spite of their higher surface area. These results reveal that photocatalytic degradation and antimicrobial effect have different mechanisms and surface activity depends strongly on surface structure. To observe effect of TiO2 and light on the morphological changes of E. coli SEM analysis of E. coli cells on the coated and uncoated glasses was performed by Prof. Dr Zekiye Suludere and Dr Demet Suludere at Gazi University after one hour irradiation. After irradiation for one hour, no obvious morphological changes of E. coli cells were recognized on the uncoated glass. By contrast, the shape of the cells, which looks like sausage, disappeared on the coated glass after one hour irradiation. The photocatalytic inactivation experiments with E. coli revealed that the addition of SiO2 enhanced the photocatalytic activity of thin films. However, addition of SiO2 reduced photocatalytic self-cleaning activity of thin films against MB stain. In addition, it was found that the specific surface area and super-hydrophilic property of thin films increased with addition of SiO2.