CHEMICAL SENSORS BASED ON SURFACE-MODIFIED SOL-GEL-COATED INFRARED WAVE-GUIDES

Attenuated total reflectance sampling, or waveguide sampling, is commo nly used to obtain infrared spectra of aqueous solutions. The detectio n limits achieved for the determination of organic analytes in aqueous solutions using waveguide sampling are limited by the strong water ab sorption features and relatively small effective sample thickness due to the short penetration depth of the evanescent wave into the sample. Sol-gel processing has been used to produce a porous silica film on t he surface of an infrared waveguide. The surface of the sol-gel film w as modified with a silanizing reagent to produce a hydrophobic surface . The resulting waveguide was used to obtain infrared spectra from sam ples of benzonitrile in water. The benzonitrile spectral features obta ined with the modified waveguide are enhanced by more than a factor of 10(3) when compared with those obtained with an unmodified waveguide.