Transmittance change of the TiO2 thin film by photoreductive deposition of Cu(II)

Photoreductive deposition of Cu(2+) on TiO(2) thin film prepared by sol-gel method has been investigated by measuring a change of transmittance of the film. The transmittance decreased with irradiation time, corresponding to a decrease of the Cu(2+) concentration in the solution. Removal percent of Cu(2+) ions from the solution was obtained to be 80-98%. On the other hand, the transmittance change (DeltaT) was greatly affected by experimental conditions: the DeltaT value increased when the thicker films or films fired at higher temperature were used or when the same film was employed repeatedly. With the initial concentrations of Cu(2+) more than 100 ppm, induction periods (I.P.) of 45-240 min were observed before the transmittance decreased. When Na(2)C(2)O(4) was used as a sacrificial donor instead of HCOONa, the decrease rate for Cu(2+), concentration in the solution became slightly lower. However, with Na(2)C(2)O(4), no induction period was observed and the DeltaT values were two times as high as those with HCOONa. (C) 2003 Elsevier B.V. All rights reserved.