FIBEROPTIC SENSORS FOR PH AND CARBON-DIOXIDE USING A SELF-REFERENCINGDYE

pH and CO2 fiber-optic sensors were prepared using self-referencing dy es from the seminaphthorhodamine family (SNARF). The ratio of the emis sion from the acid and base tautomers of these dyes is insensitive to photobleaching and variations in the excitation intensity. The photoph ysics of the dyes has been determined. At high concentrations formatio n of nonfluorescent aggregates of the dyes results in reduced emission yields. The fluorescent lifetimes of the dyes are unaffected by conce ntration. The pK(a) of the dye-polymer composite is sensitive to the s tructure of the polymer. This sensitivity is attributed to a differenc e in energy of the conjugate base of the dye as a function of the amou nt of cross-linking of the polymer. The pH sensors show mpH response i n the physiological pH range (6.8-7.8) and fast hydration and response times. The CO2 sensors show 1-2 Torr response with partial pressures of CO2 in the range of 10-100 Torr and have response and hydration tim es on the order of several minutes.