The best acetone sensing performance was achieved in the In₂O₃ sample with the Au doping method.

Elaborating the sensitization effects of different noble metals on In ₂ O ₃ has great significance in providing an optimum method to improve ethanol sensing performance. In this study, long-range ordered mesoporous In ₂ O ₃ has been fabricated through replicating the structure of SBA-15. Different noble metals (Au, Ag, Pt and Pd) with the same doping amount (1 at%) have been introduced by an in situ doping routine. The results of the gas sensing investigation indicate that the gas responses towards ethanol can be obviously increased by doping different noble metals. In particular, the best sensing performance towards ethanol detection can be achieved through Pd doping, and the sensors based on Pd-doped In ₂ O ₃ not only possess the highest response (39.0–100 ppm ethanol) but also have the shortest response and recovery times at the optimal operating temperature of 250 °C. The sensing mechanism of noble metal doped materials can be attributed to the synergetic effect combining ‘catalysis’ and ‘electronic and chemical sensitization’ of noble metals. In particular, the chemical state of the noble metal also has a great influence on the gas sensing mechanism. A detailed explanation of the enhancement of gas sensing performance through noble metal doping is presented in the gas sensing mechanism part of the manuscript.