SOL-GEL COATINGS FOR OPTICAL CHEMICAL SENSORS AND BIOSENSORS

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