Self-Assembly Template Driven 3D Inverse Opal Microspheres Functionalized with Catalyst Nanoparticles Enabling a Highly Efficient Chemical Sensing Platform

The design of semiconductor metal oxides (SMOs) with well-ordered porous structure has attracted tremendous attention owing to their larger specific surface area. Herein, three-dimensional inverse opal In₂O₃ microspheres (3D-IO In₂O₃ MSs) were fabricated through one-step ultrasonic spray pyrolysis (USP) which employed self-assembly sulfonated polystyrene (S-PS) spheres as a sacrificial template. The spherical pores observed in the 3D-IO In₂O₃ MSs had diameters of about 4 and 80 nm. Subsequently, the catalytic palladium oxide nanoparticles (PdO NPs) were loaded on 3D-IO In₂O₃ MSs via a simple impregnation method, and their gas sensing properties were investigated. In a comparison with pristine 3D-IO In₂O₃ MSs, the 3D-IO PdO@In₂O₃ MSs exhibited a 3.9 times higher response (R_air/R_gas = 50.9) to 100 ppm acetone at 250 °C and a good acetone selectivity. The detection limit for acetone could extend down to ppb level. Furthermore, the 3D-IO PdO@In₂O₃ MSs-based sensor also possess good long-term stability. The extraordinary sensing performance can be attributed to the novel 3D periodic porous structure, highly three-dimensional interconnection, larger specific surface area, size-tunable (meso- and macroscale) bimodal pores, and PdO NP catalysts.