Copper-aided photo sterilization of microbial cells on TiO2 film under irradiation from a white light fluorescent lamp

The copper-aided photosterilization of Escherichia coli was examined on TiO2 thin films under a lighting condition with less UV rays from a white light fluorescent lamp. It was found that the coexistence of Cu2+ and H2O2 in liquid phase exerted the synergistic effect on killing E. coli cells though these chemical species were individually at nontoxic levels to the cells (less than 10 mmol/m(3)). At an incident light intensity of I-0 = 28 W/m(2), the addition of Cu2+, (10 mmol/m(3)) to liquid phase on TiO2 film gave the apparent deactivation rate constant of k' = 12 x 10(-2) min(-1), the value of which was about 5 times as large as that on TiO2 film in the absence of Cu2+. This result suggested that in the liquid phase, CU2+ was reduced to Cu+ by receiving electron from photo-excited TiO2, and then Cu+ reacted with photocatalysis-derived H2O2 to produce (OH)-O-center dot via Fenton-type reaction. The deactivation tests were also examined using a modified film preparation made from copper-incorporated TiO2. On this film, the k' value was 23 x 10(-2) min(-1) at 10 = 28 W/m(2), which was respectively about two and nine times as large as those on the original TiO2 film with and without Cu2+ addition (10 mmol/m(3)). The enhancement of biocidal activity on the modified TiO2 film was considered to arise from promoted (OH)-O-center dot formation by the aid of copper component anchored in TiO2 solid phase. (c) 2006 Elsevier B.V. All rights reserved.