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

A highly porous Fe2O3-SiO2 layer prepared using sol-gel and spin-coating methods was applied on the surface of a surface acoustic wave (SAW) device for H2S sensing. SiO2 in this sensing layer serves as a porous support for dispersing Fe2O3 nanoparticles, and Fe2O3 nanoparticles can effectively adsorb and react with H2S molecules. By changing the Fe/Si molar ratio in this Fe2O3-SiO2 layer, its pore volume, pore distribution and H2S 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 H2S, with a good selectivity and reproducibility operated at room temperature (25 ℃)