Fiber optic chemical sensors: sol-gel approach

Remote sensing in environmental applications has been widely employed as an alternative to traditional sampling methods. Fluorometric techniques have become one of the most popular methods of detection because of high sensitivities and simplicity of equipment, and have allowed the measurement of numerous toxic organic and inorganic materials. Laser excitation linked with fiber optic transmission make even the most remote environment accessible. By placing fluorogenic reagents at the tip of the fiber optic system, non-fluorescent analytes may react with the indicator dyes to change the fluorescent properties in the sensing volume, and this change can be used to determine the concentration of the analyte. The sol-gel method allows the encapsulation of a fluorophor into a porous network, through which the analyte can diffuse. In this work we prepare fiber optic chemical sensors replacing a commercial fiber cladding by a sol-gel thin film doped with the fluorophor. We show results for a salinity sensor based on the Mg++ detection by the fluorescent complex formation with 8-hydroxyquinoline-5-sulfonic-acid ligand.