Influence of major parameters on the sensing mechanism of semiconductor metal oxide based chemiresistive gas sensors: A review focused on personalized healthcare

In this review, the different important parameters having significant effects on the sensing behavior of semiconductor metal oxide (SMO) based chemiresistive gas sensors have been discussed in details. Recently, SMO based chemiresistive sensors have shown immense potential in multifarious applications, especially human volatilome-based disease detection and health monitoring. In this work, we have selected some of the materials and operating condition aspects, viz. particle size and morphology, porosity, doping by noble metals and aliovalent ions, crystal phases and selectively exposed highly reactive crystalline planes, humidity, operating temperature, oxide heterojunction, homojunction and complex oxides, acid-base interaction between an oxide and a gas, gas molecule reformation inside sensing layer/ catalytic overlayer and interface gas filtration, light activation etc. and systematically reviewed their effects on the gas sensing performance of SMO sensors. From the perspective of practical applications, long-term stability, and high-throughput synthesis techniques have been elaborated. The future scope of the SMO-based breath and skin gas sensors in the upcoming area of skin mounted/wearable devices for personalized healthcare has been elucidated briefly. Finally, the discussions have been summarized with the major takeaways of this work.