Highly sensitive and selective trimethylamine sensor using one-dimensional ZnO–Cr2O3 hetero-nanostructures

Abstract

Highly selective and sensitive detection of trimethylamine (TMA) was achieved by the decoration of discrete p-type Cr2O3 nanoparticles on n-type ZnO nanowire (NW) networks. Semielliptical Cr2O3 nanoparticles with lateral widths of 3–8 nm were deposited on ZnO NWs by the thermal evaporation of CrCl2 at 630 °C, while a continuous Cr2O3 shell layer with a thickness of 30–40 nm was uniformly coated on ZnO NWs at 670 °C. The response (Ra/Rg: Ra, resistance in air; Rg, resistance in gas) to 5 ppm TMA of Cr2O3-decorated ZnO NWs was 17.8 at 400 °C, which was 2.4 times higher than that to 5 ppm C2H5OH and 4.3–8.4 times higher than those to 5 ppm p-xylene, NH3, benzene, C3H8, toluene, CO, and H2. In contrast, both pristine ZnO and ZnO (core)–Cr2O3 (shell) nanocables (NCs) showed comparable responses to the different gases. The highly selective and sensitive detection of TMA that was achieved by the deposition of semielliptical Cr2O3 nanoparticles on ZnO NW networks was explained by the catalytic effect of Cr2O3 and the extension of the electron depletion layer via the formation of p–n junctions.