Fresh TiO 2 was found to possess a strong germicidal activity even without UV irradiation. Live Yeast ( Saccharomyces cerevisiae ) cells in contact with fresh TiO 2 were found deformed and dead after 15 min contact. The cause of germicidal activity was discussed from the observed cell deformation, lysis and increased absorption at 1680 cm −1 in FT-IR spectra of the affected cells, which proved the oxidizing effect of fresh TiO 2 to cells. The deformation caused by the stretching of cell wall and pressure built-up inside the cell, led to cell burst and release of intracellular materials. The degree of cell deformation was found positively related with the wetting property of TiO 2 . Cells are negatively charged, for Gram-negative cell (thinner cell wall), a higher germicidal effect was observed than Gram-positive cells. The germicidal effect of TiO 2 gradually decreased after exposure to air at room temperature, as the wetting property decreased. This kind of germicidal activity was more effective compared to other germicidal process such as UVA/TiO 2 or Ag + . This shed light on designing new germicidal material either maintained by visible light irradiation, or by oxidation effect generated by reactive oxygen species.
