A technology to make integrated optical chemical gas sensors using sol-gel surfactant-templated mesoporous thin films was demonstrated. The sensor was prepared by dip coating of an ordered mesoporous silica thin film onto a tapered thin Ti O2 layer sputtered on top of a tin-diffused glass waveguide. The sensor employs single-beam polarimetric interferometry to detect molecular adsorption in the mesoporous silica film because the adsorption can lead to a change of the phase difference (Δφ) between the fundamental transverse electric (TE0) and magnetic (TM0) modes propagating in the waveguide. The sensor is sensitive to humidity and N H3 gas at room temperature (RT). The sensitivity of Δφ>180° was detected for 40 min exposure of the sensor to 2 ppm of N H3 in dry air. The sensor was recoverable from the H N3 exposure but its recovery was too slow to cause a detectable Δφ per unit time. The slow response and recovery of the sensor were ascribed to slow diffusion of gaseous molecules in the laterally oriented tube-like pores of the silica film.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)