UV-Assisted ppb-Level Ammonia Detection of a WSe2/SnO2 Heterostructure at Room Temperature

In this work, a WSe2/SnO2 heterostructure is prepared by hydrothermal synthesis. The attachment of SnO2 to flower-like WSe2 nanosheets can generate gas transmission and n–n heterojunction, resulting in improved sensitivity and decreased response/recovery time. The response of the WSe2/SnO2 sensor toward NH3(183) is higher than those of pure WSe2(15.6) and SnO2(41.5). Under ultraviolet-light (UV-light) irradiation, the sensitivity of the WSe2/SnO2 composite is further improved and its low detection limit is significantly reduced. The sensitivity of WSe2/SnO2 exposed to 1 ppm of NH3 is increased by 200%, and its low detection limit concentration is 50 ppb (1.18). In addition, the adsorption mechanism of NH3 is explained by density functional theory (DFT) calculation. The formation of the heterojunction was demonstrated by analyzing the X-ray photoelectron spectroscopy (XPS) spectra. The results show that the UV-activated WSe2/SnO2 heterostructure can detect NH3 sensitively at room temperature.