SOL-GEL-DERIVED OPTICAL COATINGS FOR DETERMINATION OF CHROMATE

An optical probe for chromate ion has been obtained by the sol-gel tec hnique by depositing a porous film containing the reagent diphenylcarb azide on a glass support. Changes in the absorption of light as a resu lt of the (irreversible) formation of a purple product between chromat e and the reagent inside the sol-gel are monitored. The detection limi t for chromate anion is as low as 1 ppb, but only after rather long ex posure to samples. The morphology of the surface of the film has been studied using atomic force microscopy and is related to the technique of preparing the film.