High performance UV-LED activated gas sensors based on ordered carbon mesoporous materials loaded with ZnO nanoparticles

Abstract

Carbon mesoporous materials (CMMs) with various ZnO loading concentrations have been fabricated as sensitive chemical sensors for nitrogen dioxide (NO2) and ammonia (NH3) detection. Mesostructured carbon with high surface area (>1000 m2/gr) is prepared using a template replication method, and zinc oxide (ZnO) nanoparticles are loaded through a facile solution impregnation. The sensors are operated at room temperature (∼25 °C) and activated by UV irradiation of a 365 nm wavelength and 25 mW/cm2 irradiance emitted from a UV-LED. SEM, TEM, XRD, XPS, and BET characterizations are carried out to study the physico-chemical properties of the prepared materials. The sensors with 57 wt% and 70 wt% ZnO loadings have exhibited superior gas sensing for the detection of NO2 and NH3, respectively. The maximum response values in optimal loading concentrations are 1.91 (NO2) and 1.35 (NH3), which are significantly higher than those of pristine ZnO nanoparticles reported previously. This improvement in response could be attributed to the high surface area, as well as the extended separation and restrained recombination rate of the photo-induced electron-hole pairs in ZnO/CMM sensing material. Furthermore, loading on CMMs produces more oxygen vacancies (OVac) induced by C-dopant, which increases the number of active sites and results in a large number of photo-induced oxygen ions on the surface, thus enhancing gas sensing activity.