Highly porous Fe2O3-SiO2 layer for acoustic wave based H2S sensing: mass loading or elastic loading effects?

A highly porous Fe 2 O 3 -SiO 2 layer prepared using sol-gel and spin-coating methods was applied on the surface of a surface acoustic wave (SAW) device for H 2 S sensing. SiO 2 in this sensing layer serves as a porous support for dispersing Fe 2 O 3 nanoparticles, and Fe 2 O 3 nanoparticles can effectively adsorb and react with H 2 S molecules. By changing the Fe/Si molar ratio in this Fe 2 O 3 -SiO 2 layer, its pore volume, pore distribution and H 2 S adsorption capacity can be adjusted, the contribution of mass loading effect and the elastic loading effect toward the frequency response of the sensor can be controlled, and the sensing performance of the sensor can be optimized. The optimized sensing response is -4.4 kHz toward 100 ppm H 2 S, with a good selectivity and reproducibility operated at room temperature (25 ℃)