Study of indicators for the development of fluorescence based optical fiber temperature sensors

An experimental study about fluorophores, which have never been used before in thermometric applications has been carried out for the development of fluorescence based temperature sensors. Fluorescent dyes like: 10-(3-sulfopropyl) acridinium betaine, quinacrine dihydrochloride, naphthofluorescein, fluorescein and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt have been immobilized on sol–gel derived coatings deposited on optical fibers by dip coating. Comparison between the characteristics of the different sensors revealed that the fluorescent dye 10-(3-sulfopropyl) acridinium betaine showed the best performances: a sensitivity around 1 °C, response time lower than 8 s in thermal transitions between 30 and 250 °C and negligible hysteresis along the dynamic range: 30–250 °C (220 °C). Extended study of cross-sensitivity and fluorescence degradation when sensors are exposed to volatile organic compounds or humidity variations has been performed with 10-(3-sulfopropyl) acridinium betaine. Consequently, methods for isolating the sensors to the effect of harmful atmospheres have also been developed.