Sol-gel composites for optical sensing of solvents

Porous sol-gel glasses containing entrapped fluorescent-labelled beta-cyclodextrin have been prepared from tetramethylorthosilicate (TMOS). Small non-polar solvent molecules such as cyclohexane and toluene displace the fluorescent label from the cyclodextrin cavity, and the resulting decrease in fluorescence intensity is proportional to the solvent vapour concentration in the range 40-100 ppm, and is reversible. Polar solvents such as acetone give no response. Strategies for optimisation of the system are discussed.