Photocatalytic antibacterial activity of TiO2–SiO2 thin films: The effect of composition on cell adhesion and antibacterial activity

Colloidal solutions of SiO2–TiO2 mixed oxides having different SiO2 contents were synthesized by sol–gel technique and thin films were deposited over glass slides by using dip coating technique. The samples were characterized by XRD, SEM, AFM and methylene blue adsorption methods. The surface free energy of thin films was measured by sessile drop method by using diiodomethane, glycerol and water as probe liquids. The photocatalytic antibacterial activity of the samples was determined for Escherichia coli XL1-blue by using artificial solar irradiation. The surface characterization studies revealed the presence of small crystallites of anatase phase, enhanced dispersion of TiO2 particles and increasing surface free energy at elevated SiO2 content. Highest photocatalytic antibacterial activity was obtained over 92 wt% SiO2 containing sample and strong correlation was found between the bacterial adhesion and antibacterial activity. Surface-adhered E. coli cells having direct contact with TiO2 particles were inactivated at a higher rate than suspended cells.