Room temperature NO2 sensing performance of a-C-decorated TeO2 nanowires

Abstract

TeO2 is a semiconducting metal oxide that is not popular for sensing studies due to its poor sensing performance in its pristine form. To enhance its sensing performance, we deposited amorphous carbon (a-C) on its surface. We first synthesized TeO2 nanowires using a thermal evaporation method, and then we deposited an a-C layer on them by a simple procedure using a flame carbon vapor deposition technique. We showed that the a-C-decorated sensor had a lower optimized sensing temperature (26 °C) relative to the pristine TeO2 sensor (50 °C) and presented a higher sensitivity to NO2 gas. The maximum responses to NO2 (10 ppm) were 1.918 and 1.468 for a-C-decorated and pristine TeO2 nanowires, respectively. Furthermore, the a-C-decorated sensor indicated outstanding selectivity toward NO2. The high performance of a-C-decorated sensor was results of its higher surface area created by the bumpy carbon layer on the surface of TeO2 nanowires as well as the electronic sensitization due to the a-C layer. We also confirmed NO2 sensing behaviors of bare and a-C-decorated TeO2 nanowires using density functional theory (DFT) calculations, where calculated binding energies between NO2 and the sensing layer were stronger for NO2 and a-C-decorated TeO2 nanowire gas sensor relative to pristine gas sensors. The present approach for enhancing the sensing of TeO2 nanowires can be extended to other sensor systems as a simple, inexpensive strategy to improve sensor performance.