SnO₂ Nanostructures Exposed with Various Crystal Facets for Temperature-Modulated Sensing of Volatile Organic Compounds

Dynamic working temperature modulation has received considerable attention as a way to enable metal oxide-based gas sensors to recognize the detected gases. Previous reports mainly focused on heating-voltage waveform manipulation and algorithm improvement, not involving the insight of the temperature modulation sensing behavior correlated with fine nanostructures of metal oxide. Here, three types of SnO2 nanoparticles with different percentages of high-energy {221} and low-energy {110} crystal facets were synthesized and assembled as gas sensors. Under a working temperature modulation by applying a square wave pulse heating voltage, their dynamic response behaviors toward volatile organic compounds (VOCs) including alcohols, aldehydes, ketones, amines, and aromatic compounds were systematically explored. The results indicated that they exhibited different characteristic response curves toward different VOCs, presenting the crystal facet-dependent temperature modulation sensing behaviors. This effect was analyzed further and explored in conjunction with the characteristic response curves. Based on their different characteristic response curves that occurred on the three types of SnO2 nanoparticles, the detected gases, and even some congeners, were well discriminated along with a simple PCA recognition algorithm. Additionally, their quantitative analysis was also achieved.