Sol–gels with fiber-optic chemical sensor potential: Effects of preparation, aging, and long-term storage

The features of sol–gels, incorporating pH-sensitive dyes, designed as potential substrates for fiber-optic chemical sensors, have been investigated in terms of a variety of characteristics resulting from the preparation methods used and following the storage of samples for a period of several years. These materials, organically doped sol–gels, have been used as the heart of a number of prototype chemical sensing instruments, and a key issue in their effective use in instrumentation is their long-term durability and stability. In this work, it has been shown that such aged gel substrates can withstand immersion in water, drying, and reimmersion without fragmenting. Such impregnated gels were shown to still exhibit strong fluorescence, although some changes to the gel structure, determined from microhardness measurements, were observed and reported, reflecting their potential for use in chemically sensitive fiber optic-based instruments.