Development of Dual-Selective Chemiresistive Sensor for NH 3 and NO x at Room Temperature Using MoS 2 /MoO 2 Heterostructures

Molybdenum oxides and sulfides stand out as promising materials for chemiresistive gas sensors. In this study, we tailored MoS 2 /MoO 2 heterostructures, adapting pyrolysis-assisted in situ sulfidation of hydrothermally grown MoO 3 by tuning the concentration of the sulfur source. The MoS 2 flakes adorning a MoO 2 cuboid rod heterostructure represent the n-type semiconducting property, confirmed by Hall measurement. Notably, the sensor demonstrated dual selectivity toward NH 3 and NO x at room temperature. To our knowledge, the dual selectivity of the MoS 2 /MoO 2 heterostructure has not been reported previously. The heterostructure, characterized by a higher carrier concentration, displayed enhanced sensitivity, yielding responses of 10.3 and 8.4% to 10 ppm of NH 3 and NO x, respectively. The lowest detection limits were 0.32 ppm for NH 3 and 0.29 ppm for NO x . Furthermore, the heterostructure sensor exhibited commendable cyclic stability and device reproducibility. A long-term stability assessment over 50 days revealed that the response of the sensor remained at 98.6 and 98.4% toward NH 3 and NO x, respectively. Our results show that the optimized n–n heterojunction between MoO 2 and MoS 2 offers superior sensitivity to NH 3 and NO x at room temperature. The results could have potential for the development of dual gas sensors suitable for real-time applications.