Synthesis of dye-impregnated sol-gel glasses for fiber optic chemical sensing

The polarity of the silica cage has been investigated by entrapping organic dyes in a silica gel. pH dyes of bromocresol purple and bromocresol green were selected for this study. The influence of pH on the polarity of the silica cage was determined by measuring the spectral shift of the dye. The pH dye- impregnated silica films show a red-shift in an acidic environment and a blue shift in basic environment, compared to those dissolved in water. This implies that the polarity of a silica cage varies after being treated by different pH solutions. The cage shows higher polarity in a basic solution than in an acidic solution.