Fluorescence-intensity changes in organic dyes impregnated in porous glass on exposure to NO2

To develop an NO2 sensor that can measure the NO2 concentration in the atmosphere, we studied changes in fluorescence intensities of dyes impregnated in porous glass when exposed to NO2 in N2 as the first step. The NO2 sensing materials were Squarylium dye 1, Squarylium dye 2, and Rhodamine B. We found that fluorescence quenching by NO2 occurred even in porous glass. The fluorescence quenching (F0/F) increased as the NO2 concentration increased in the range of 0.2–12.3 ppm, with an almost linear relationship. The minimum detectable concentration of NO2 was 0.2 ppm.