Enhanced room-temperature NO2 gas sensing with TeO2/SnO2 brush- and bead-like nanowire hybrid structures

Abstract

We have synthesized two highly sensitive, room-temperature operating TeO2/SnO2 gas sensors with hierarchical nanowire structures. One is a brush-like nanostructure, from a two-step thermal vapor-transport route, and the other one is a TeO2/SnO2 bead-like nanostructure, from annealing of the former. The TeO2/SnO2 nanostructures exhibit a greatly enhanced room-temperature gas-sensing response compared to pristine TeO2 nanowires in the sequence: TeO2/SnO2 bead-like structure > brush-like structure > pristine TeO2 nanowire. The response of the TeO2/SnO2 bead-like structure is in a range of 10 to 20 against NO2 gas of ppm levels (3–100 ppm) at room temperature. This compares favorably to the response, smaller than 2, for the pristine TeO2 nanowires. Interestingly, the TeO2/SnO2 bead-like structure exhibits a typical n-type gas-sensing behavior, in contrast to the p-type behavior from the brush-like and the pristine TeO2 structures. Possible hybrid growth and sensing mechanisms are discussed.