Highly Sensitive NO Gas Sensors Based on MoS@MoO Magnetic Heterostructure.

Recently, two-dimensional (2D) materials and their heterostructures have attracted considerable attention in gas sensing applications. In this work, we synthesized 2D MoS@MoO heterostructures through post-sulfurization of α-MoO nanoribbons grown via vapor phase transport (VPT) and demonstrated highly sensitive NO gas sensors based on the hybrid heterostructures. The morphological, structural, and compositional properties of the MoS@MoO hybrids were studied by a combination of advanced characterization techniques revealing a core-shell structure with the coexistence of 2H-MoS multilayers and intermediate molybdenum oxysulfides on the surface of α-MoO. The MoS@MoO hybrids also exhibit room-temperature ferromagnetism, revealed by vibrating sample magnetometry (VSM), as a result of the sulfurization process. The MoS@MoO gas sensors display a -type-like response towards NO with a detection limit of 0.15 ppm at a working temperature of 125 °C, as well as superb selectivity and reversibility. This -type-like sensing behavior is attributed to the heterointerface of MoS-MoO where interfacial charge transfer leads to a -type inversion layer in MoS, and is enhanced by magnetic dipole interactions between the paramagnetic NO and the ferromagnetic sensing layer. Our study demonstrates the promising application of 2D molybdenum hybrid compounds in gas sensing applications with a unique combination of electronic and magnetic properties.