Preparation and antibacterial activities of Ag-doped SiO2–TiO2 composite films by liquid phase deposition (LPD) method

In the present study, Ag/SiO2–TiO2 thin films on ceramic tiles with glazed surface were successfully prepared by a liquid phase deposition method (LPD) at a low temperature. The Ag/SiO2–TiO2 thin films obtained were homogenous, well adhered and colored by interference of reflected light. The films were characterized by scanning electron microscopy and X-ray diffraction. From these analysis data, it was found that silver (Ag) nanoparticles were trapped in SiO2–TiO2 matrix. The antibacterial effects of Ag/SiO2–TiO2 thin films against S. aureus and E. coli were examined by the so-called antibacterial-drop test. The bactericidal activity for the above bacteria cells was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The Ag/SiO2–TiO2 thin films had an excellent antibacterial performance. Atomic absorption spectroscopy (AAS) was used for the quantitative determination of the Ag ion concentration releasing from the Ag/SiO2–TiO2 thin film. The releasing rate of Ag ions from the Ag/SiO2–TiO2 film is 0.123 μg/mL during 192 h. The antibacterial effect of Ag/SiO2–TiO2 thin film before and after aging in a weathering chamber for 48 h was compared and the results show that the antibacterial activity is not compromised after weathering.