IMPREGNATION OF A PH-SENSITIVE DYE INTO SOL-GELS FOR FIBER OPTIC CHEMICAL SENSORS

The sol-gel method was used to investigate the preparation of gels whi ch were subsequently impregnated with a pH-sensitive fluorescent dye, fluorescein isothiocyanate (FITC). The work enabled the examination of several aspects of the system, including the leaching of the dye from the gel, a problem which has more severe consequences for fluorescenc e-based than absorption-based systems, where the use of a silylating a gent was found to improve the immobilization of the dye to the substra te. The effect of the loss of dye was investigated in terms of the flu orescent response of the prepared gels, and this was cross-compared wi th that of the dye in solution, as a function of pH. This showed good agreement. The response time of the gel to pH changes was also observe d. Further, aspects of the drying of the gels were investigated in ter ms of their physical appearance and the characteristics of the substra tes thus produced for chemical sensing purposes. Various observations of failure characteristics of these gels under re-immersion in a ater were considered in light of their potential use, in chemical sensor pr obes, of sol-gel based systems.