Abstract:

A highly sensitive hydrogen sulfide gas sensor was developed by immobilization of thionine dye doped polyvinyl alcohol film onto the surface of a K⁺ exchanged glass optical waveguide via a spin-coated method. The sensing film presents a color change from purple to colorless when exposed to H₂S gas, causing a decrease in the evanescent wave absorption of the film, and an increase of the output light intensity of the sensor(signal). The sensor performance was tested for the detection of H₂S gas by controlled flow injection. The experimental result shows that the sensor has a good linear response(r=0.99667) to H₂S gas in a range of 56 mg/m³ to 0.14 mg/m³. The detection limit for H₂S is 0.11 mg/m3(S/N=3). The RSD of output light intensity is 4.0% and response time(t90)＜2 s. This sensor shows high sensitivity, fast response, good reversibility and repeatability.

Key words: sensor, optical waveguide, film, hydrogen sulfide