AuPd bimetallic functionalized monodisperse In2O3 porous spheres for ultrasensitive trimethylamine detection

The use of bimetallic nanoparticles (NPs) to enhance the performance of oxide semiconductor gas sensor is a promising approach. In this work, monodisperse In2O3 porous spheres were synthesized by a simple hydrothermal method, and bimetallic AuPd NPs were decorated on In2O3 nanospheres by in-situ redox reaction, then Au, Pd and AuPd-modified In2O3 were obtained. Characterization results of SEM and TEM showed that the as-synthesized materials had monodisperse porous sphere morphology with uniform diameter of within 300 nm. The gas sensing test results showed that AuPd-In2O3 sensor has excellent gas sensing performance, specifically, lower detection limit (300 ppb, 1.35), and an ultra-short response time (2 s), as well as a high response to 100 ppm trimethylamine (TMA) (Ra/Rg=367.0) which was 12, 127 and 334 times higher than that of Pd-In2O3 (Ra/Rg=30.3), Au-In2O3 (Ra/Rg=2.9) and pristine In2O3 (Ra/Rg=1.1). The gas sensor also has a good long-term stability, repeatability, and cross-selectivity. The mechanism of enhanced gas sensing performance was proposed combining with chemical sensitization of Au, electronic sensitization of Pd, and synergetic catalytic effect of AuPd bimetallic NPs. This work provides a promising material for the design and preparation of gas sensors for TMA detection.