pH Effect on the Optical Properties of Peroxo-Titanium Complex

Abstract

ABSTRACTInteresting optical properties of peroxo-titanium hydrogen peroxide complex against pH changes were studied for the first time using an analytical UV-VIS spectrophotometer. A freshly prepared peroxo titanium complex with pH value of 2.21 exhibited an orange color. This color changed to light orange, cloudy yellow, and then translucent pale-yellow as its pH value increased to 3.9, 5.8 and 6.7 or above. UV-VIS spectra show that the fresh complex had an absorption band rising at wavelength around 400 nm to higher energy, but had no maximum peak. A new absorption peak appears at 245nm for the cloudy yellow samples. This is similar to that of colloidal TiO2, which suggests that TiO2 particles might form upon increasing pH value to or above 5.80. The formation of TiO2 particles was accelerated in the pH value range from 6 to 9, but not in the acidic environment. In H2SO4 acidified environment, the color turned red-orange instead, and a strong absorption at 397nm was observed only at pH =0.99. Based on the experimental observations, a model for the color-forming species and possible applications by using the techniques generated from the present study were proposed.