Self-Assembly Template Driven 3D Inverse Opal Microspheres Functionalized with Catalyst Nanoparticles Enabling a Highly Efficient Chemical Sensing Platform WangTianshuang CanInci ZhangSufang HeJunming SunPeng LiuFangmeng LuGeyu 2018 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 In<sub>2</sub>O<sub>3</sub> microspheres (3D-IO In<sub>2</sub>O<sub>3</sub> 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 In<sub>2</sub>O<sub>3</sub> MSs had diameters of about 4 and 80 nm. Subsequently, the catalytic palladium oxide nanoparticles (PdO NPs) were loaded on 3D-IO In<sub>2</sub>O<sub>3</sub> MSs via a simple impregnation method, and their gas sensing properties were investigated. In a comparison with pristine 3D-IO In<sub>2</sub>O<sub>3</sub> MSs, the 3D-IO PdO@In<sub>2</sub>O<sub>3</sub> MSs exhibited a 3.9 times higher response (<i>R</i><sub>air</sub>/<i>R</i><sub>gas</sub> = 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@In<sub>2</sub>O<sub>3</sub> 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.