Development of Dual-Selective Chemiresistive Sensor for NH<sub>3</sub> and NO<sub><i>x</i></sub> at Room Temperature Using MoS<sub>2</sub>/MoO<sub>2</sub> Heterostructures
K. Muthumalai, Mathankumar Manoharan, Kamaraj Govindharaj, Poovarasan Saravanan, Yuvaraj Haldorai, Zdeněk Sofer, Ramasamy Thangavelu Rajendra Kumar
Abstract
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.