Fabrication of Pt cluster-loaded In2O3 inverse opal photonic crystals for fast and highly sensitive ethanol sensing

The high porosity of the three-dimensional ordered macroporous structure of inverse opal photonic crystals (IOPCs) provides an ideal platform for gas sensing based on metal oxide semiconductors. Herein, Pt cluster-loaded In2O3 IOPCs were fabricated, and displayed a significantly improved response to ethanol. Various characterization techniques were used to verify the successful preparation of Pt cluster-loaded In2O3 IOPCs. In2O3 IOPCs exhibit closely arranged three-dimensional (3D) ordered macroporous structures, which contain periodic voids with an average diameter of about 150 nm and a uniform wall thickness of 20 nm. Their gas sensing performance is significantly improved at a Pt cluster loading of 2.0 wt%. Gas sensor tests showed that Pt cluster-loaded In2O3 IOPC sensors exhibited an excellent ethanol response (R-a/R-g = 103 to 50 ppm at 240 degrees C), which was more than 5 times higher than the response of pure In2O3 IOPCs. The sensor also demonstrated an ultra-fast response/recovery time (7/9 s), impressive selectivity, reproducibility, and long-term stability. The significantly enhanced sensing performance of Pt cluster-loaded In2O3 IOPCs is attributed to the synergistic effects of the connected 3D ordered macroporous structure, chemical and electronic sensitization of Pt nanoparticles, and p-n heterojunctions between p-type PtO, p-type PtO2 and n-type In2O3. The present findings are expected to provide enlightening insights into the design and fabrication of gas sensors with an ultra-high response and an ultra-fast response/recovery speed.