The increases in catalytic photolysis efficiency of the surface modified ATO (anodic titanium oxide) by Ag or/and Au nanoparticles were attributed to the greater light absorbance than that of the sole ATO. In addition to the enhanced inherent ATO absorbance at 365 nm inasmuch as the surface-plasmon enhancement of the band emission, additional light absorbance peak occurred at the wavelength around 430 nm, 530 nm and 500 nm for nano Ag modified TiO2, nano Au modified TiO2, and composite nano Ag/Au modified TiO2, respectively. All surface modified ATO catalysts exhibited stronger bactericidal effect under UV exposure than under visible light exposure for 24 hrs. Even for a short time of one hour, survival of E. coli decreased drastically from 106 CFU under the dark control to 102 CFU under the UV exposure, which was about four powers of exponent reduction. Surfaces modified ATO catalysts need to take longer time exposure under visible light irradiation than under UV irradiation to achieve the similar photocatalytic efficiency

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