Chemical sensors based on hydrophobic porous sol-gel films and ATR-FTIR spectroscopy
A new chemical sensor based on attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy has been fabricated by coating an ATR crystal with a hydrophobic mesoporous silica film. The highly porous coating can extract hydrophobic analytes, such as benzene, from aqueous solutions and concentrate them inside the film. The enrichment of the analytes inside the film provides the sensor with enhanced sensitivity. The hydrophobic porous film can efficiently exclude water from the region probed by the evanescent wave, thus eliminating the spectral interference due to water absorption bands. Measurement of nitrogen adsorption and desorption isotherms of the films using surface acoustic wave techniques has been used to characterize the pore structure of the films. Relationships between the structure of the porous film and sensor performance are discussed.