Room-Temperature High-Performance Ammonia Gas Sensing Based on Molybdenum Trioxide Nanobelts Thin-Film

Abstract

Ammonia, a kind of ubiquitous gas with poisonous, colorless and a strong pungent odor, is widely applied in fields of chemistry, architecture, food refrigeration, and so on. Excessive ammonia gas (NH3) in the atmosphere may promote the formation of haze, further bringing about environmental pollution. Besides, for humans, NH3 with high concentration can damage many organs such as eyes, skin and respiratory organs, causing tears, sore throat, and even pulmonary edema and death. Therefore, sensitive and rapid detection of the leakage or emission of low-concentration NH3 is of great significance in the fields of human health diagnosis, home air safety, and gas environment monitoring. To achieve this goal, in this work, molybdenum trioxide (MoO3) nanobelts were successfully synthesized by utilizing an in-situ facile one-step hydrothermal method with the help of concentrated hydrochloric acid, and then as-synthesized MoO3 nanobelts were sprayed onto interdigital electrodes substrates to construct thin-film chemiresistive sensors. The sensitive material was characterized by multiple characterization techniques such as XRD, SEM, TEM, BET and Raman, and its gas-sensing performance was systematically investigated. At optimum operation temperature (room temperature, 25±2 ℃), the sensor based on MoO3 nanobelts exhibited a high gas sensitivity response of ~17% towards NH3 with a concentration of 5 ppm, accompanied by a fast response speed of ~60 s and full recovery. It was one of the best cases of NH3 sensors based on MoO3 nanomaterials, taking into account the operation temperature and gas response. In addition, the sensor displayed a good selectivity to NH3 over other potential interfering gases including CO, CO2, H2S and SO2, as well as good humidity resistance. Besides, MoO3 sensor possessed a fine limit of detection of 25 ppb by calculating the ratio of triple mean square error of the background signal to the sensor’s sensitivity. These excellent gas-sensing performance to NH3 was attributed to the porosity of MoO3 nanoribbons, and the interspaces between nanobelts that facilitate gas accessibility and interaction between gas molecules and nanomaterials. More important, these results showed that the as-prepared MoO3 sensor had great potential for efficient and real-time monitoring of low-concentration NH3 emissions at room temperature, which also provided a feasible alternative for low-power NH3-sensitive sensors based on metal oxide semiconductor nanomaterials.