Optimization of the Pt Nanoparticle Size and Calcination Temperature for Enhanced Sensing Performance of Pt-Decorated In₂O₃ Nanorods

The surface-to-volume ratio of one-dimensional (1D) semiconductor metal-oxide sensors is an important factor for achieving good gas sensing properties because it offers a wide response area. To exploit this effect, in this study, we determined the optimal calcination temperature to maximize the specific surface area and thereby the sensitivity of the sensor. The In2O3 nanorods were synthesized by using vapor-liquid-solid growth of In2O3 powders and were decorated with the Pt nanoparticles by using a sol-gel method. Subsequently, the Pt nanoparticle-decorated In2O3 nanorods were calcined at different temperatures to determine the optimal calcination temperature. The NO2 gas sensing properties of five different samples (pristine uncalcined In2O3 nanorods, Pt-decorated uncalcined In2O3 nanorods, and Pt-decorated In2O3 nanorods calcined at 400, 600, and 800 ◦ C) were determined and compared. The Pt-decorated In2O3 nanorods calcined at 600 ◦ C showed the highest surface-to-volume ratio and the strongest response to NO2 gas. Moreover, these nanorods showed the shortest response/recovery times toward NO2. These enhanced sensing properties are attributed to a combination of increased surface-to-volume ratio (achieved through the optimal calcination) and increased electrical/chemical sensitization (provided by the noble-metal decoration).