SOL-GEL COATINGS FOR OPTICAL CHEMICAL SENSORS AND BIOSENSORS

In this paper an overview is presented of the state-of-the-art of opti cal sensors employing sol-gel-derived coatings. The technique is parti cularly suited to the side-coating of optical fibres or waveguides in evanescent-wave sensors because precise control of sensitivity-determi ning parameters, such as the coating thickness and length, is achievab le. Sensors based on entrapped organic and inorganic dyes, enzymes and other biomolecules have been reported. The main features of the proce ss are illustrated by examples of chemical sensors and biosensors from the literature. In particular, the development of an oxygen sensor ba sed on the quenching of fluorescence from a sol-gel-entrapped rutheniu m complex and an absorption-based pH sensor are described. Issues that require further investigation before this technology can proceed to t he stage of industrial development are also highlighted.