Functionalized Tin Oxide Nanofibers as an Excellent Hydrogen Cyanide Gas Sensor with Part Per Billions Low Detection Limit

As a base compound for several important organic products and chemical warfare agents, it is critical to develop a hydrogen cyanide (HCN) gas sensor with low detection limit to mitigate hazardous gas exposure. Pristine and functionalized tin oxide (SnO 2 ) nanofibers with various noble metals (i.e., gold (Au), platinum (Pt), and silver (Ag)) were synthesized using electrospinning followed by calcination to test toward HCN at various operating temperatures. The oxygen concentration dependent power law exponent, n, and energy barrier, E b, of synthesized nanofibers were systematically characterized prior to HCN exposure studies determined predominated adsorbed ionized oxygen species. It was concluded that noble metal functionalization significantly alters the adsorbed ionic oxygen species and adsorption rate compared to pristine SnO 2 nanofibers, which resulted in an enhanced HCN sensing performance. At 450 °C, 5 wt% Au functionalized tin oxide nanofibers show excellent HCN sensing performance with the experimentally determined low detection limit (LOD) of 2.5 ppb. At this condition, O 2− was the predominant absorbed oxygen species altering the double Schottky barrier between the nanofibers. Through such quantitative analysis, the sensing mechanism toward HCN is proposed.