Modeling and Comparing Gas Sensing Properties of CNT and CNT Decorated With Zinc Oxide

Abstract

The use of hybrid nanostructures is of great interest to take advantage of their constructing components. However, the reason for the improved features of these structures has not yet been fully explained and there are some ambiguities. So we studied and compared sensing properties of carbon nanotube (CNT) and CNT decorated with zinc oxide (ZnO) nanoparticle (CNT/ZnO). Studied target gas molecules were CH4, CO, H2S and NO2. Different performance of CNT and CNT/ZnO structures were defined by calculating their density of sates before and after gas adsorption. The adsorption energy of molecules on both structures and charge transfer between molecules and their surfaces were also estimated using density functional theory (DFT) method. Compared to the pristine CNT, electrical properties of CNT/ZnO is influenced more notably according to the gas adsorption as the molecules have higher adsorption energy and larger charge transfer with the structure. Thus, the band gap of CNT/ZnO is also more affected by gas adsorption. The relation between band gap variations and the gas response of the structures was modeled and showed that the greater the band gap changes due to a gas adsorption, the better the structure gas sensing responses to it. Therefore, it can be concluded that the ZnO decorated CNT shows better gas sensing properties.