Room temperature vanadium dioxide–carbon nanotube gas sensors made via continuous hydrothermal flow synthesis

Abstract

Vanadium dioxide–carbon nanotube (VO2–CNT) nanocomposite materials were produced via a continuous hydrothermal flow synthesis (CHFS) method. The composites were made in a single step from CHFS using dispersions of commercially available single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) in a metal salt solution (aq.). The room temperature gas sensing characteristics of the VO2-CNT nanocomposites were investigated and compared with sensors of CHFS-made VO2 without added carbon. The VO2-CNT nanocomposites were found to display high sensitivity to H2O vapour, showing excellent potential as humidity sensors. Furthermore, p-type responses to ammonia gas were observed, with the VO2 (no carbon) sensors showing the largest response. Overall, surface composition and microstructure were found to greatly influence sensor responses to H2O vapour and NH3 gas.