Doped sol-gel glasses as chemical sensors

It is reported that by trapping suitable analytical reagents, porous sol-gel glasses can be used for the preparation of a wide variety of chemical-sensing materials. The key to the successful preparation of these materials is based on the observation that a substantial fraction of the trapped molecules is exposed to the liquid or gaseous intra-pore volume. The glass matrix thus serves as a solid support for analytical reagents which interact with analyzates present in the adjacent phase. The phenomenon is quite general, and has been demonstrated for a variety of color tests for metal cations, proton (pH indication), anions, and organic molecules.