CHEMICAL SENSORS BASED ON HYDROPHOBIC POROUS SOL-GEL FILMS AND ATR-FTIR SPECTROSCOPY

A new chemical sensor based on attenuated total reflectance-Fourier tr ansform infrared (ATR-FTIR) spectroscopy has been fabricated by coatin g an ATR crystal with a hydrophobic mesoporous silica film. The highly porous coating can extract hydrophobic analytes, such as benzene, fro m aqueous solutions and concentrate them inside the film. The enrichme nt of the analytes inside the film provides the sensor with enhanced s ensitivity. The hydrophobic porous film can efficiently exclude water from the region probed by the evanescent wave, thus eliminating the sp ectral interference due to water absorption bands. Measurement of nitr ogen adsorption and desorption isotherms of the films using surface ac oustic wave techniques has been used to characterize the pore structur e of the films. Relationships between the structure of the porous film and sensor performance are discussed.