Silver-doped TiO2 prepared by microemulsion method: Surface properties, bio- and photoactivity

A series of Ag-TiO2 photocatalysts were obtained in microemulsion system (water/AOT/cyclohexane), using several Ag precursor amounts ranging from 1.5 to 8.5 mol.%. The photocatalysts’ characteristics by X-ray diffraction, STEM microscopy, UV–vis spectroscopy, X-ray photoelectron spectroscopy, BET methods showed that a sample with the highest photo- and bioactivity had anatase structure, about 90 m2/g specific surface area, absorbed light over 400 nm and contained 1.64 at.% of silver (0.30 at.% of Ag0 and 1.34 at.% of Ag2O) and about 13 at.% of carbon in the surface layer. The photocatalytic activity of the catalysts was estimated by measuring the decomposition rate of phenol in 0.21 mM aqueous solution under visible and ultraviolet light irradiation. The bioactivity of silver-doped titanium dioxide nanocomposites was estimated using bacteria Escherichia coli and Staphylococcus aureus, yeast Saccharomyces cerevisiae and pathogenic fungi belonging to Candida family. All modified powders showed localized surface plasmon resonance (LSPR) in visible region with almost the same position of LSPR peaks indicating that similar sizes of silver, regardless of used amount of Ag, is deposited on titania particles during microemulsion method. STEM microscopy revealed that almost 50% of observed silver nanoparticles deposited at the TiO2 surface are in the range from 5 to 10 nm.