Surface gas sensing kinetics of a WO3 nanowire sensor: part 1—oxidizing gases

Abstract

The gas-sensing mechanism of a one-dimensional nanowire gas sensor was studied based on examination of adsorption–desorption kinetics of oxidizing gases of O2 and NO on a highly porous WO3 nanowire ensemble structure. An identical sensor of a single diameter was used for the examination. The test gases were diluted in either dry air or nitrogen, and reaction temperatures were fixed or varied. We show that the Langmuir adsorption theory applies to the gas surface reactions, and that the detection limit and selectivity of a gas species on a sensor material is determined by the adsorption–desorption reaction kinetics on the surface. Mixed gases, however, interact with each other in the adsorption–desorption processes. The sensor response-and-recovery kinetics is connected to the nanowire conductance in our proposed electron depletion model for nanowire sensors.