Enhancing gas sensing performance of tungsten trioxide (WO3) nanofibers through diameter and crystallinity control

Tungsten trioxide (WO3) is one of most widely investigated metal oxide semiconductors as gas sensing material because of tunable sensing performance toward different analytes through composition modulation (e.g., dopants) and various morphology and crystallinity. In this work, we synthesized WO3 nanofibers with different diameter and crystallinity through electrospinning of ammonium metatungstate hydrate (AMH)/polyvinyl pyrrolidone (PVP) nanofibers via design of experiments (DOE) followed by thermal heat treatment with the smaller average diameter being 23.0 nm. Through varying the calcination process, WO3 nanofibers with different crystallinity were also synthesized, with the smaller average grain size being 23.0 nm. These nanofibers were then exposed to many analytes (i.e., H2S, acetone, toluene, ethanol, ethyl benzene, NO2, NO, and methane) under different operating temperatures (i.e., 250 to 450 °C) to investigate their effect toward sensing response. These systematic studies indicated that nanocrystalline WO3 nanofibers with the smaller diameter (i.e., 20 nm) and/or smaller average grain sizes (i.e.,18.7 nm) exhibited best sensing performance independent of target analytes. The barrier energy was also correlated with the gas sensing performance experimentally.