Recently, two-dimensional (2D) materials and their heterostructures have attracted considerable attention in gas sensing applications. In this work, we synthesized 2D MoS₂@MoO₃ heterostructures through post-sulfurization of α-MoO₃ nanoribbons grown via vapor phase transport (VPT) and demonstrated highly sensitive NO₂ gas sensors based on the hybrid heterostructures. The morphological, structural, and compositional properties of the MoS₂@MoO₃ hybrids were studied by a combination of advanced characterization techniques revealing a core-shell structure with the coexistence of 2H-MoS₂ multilayers and intermediate molybdenum oxysulfides on the surface of α-MoO₃. The MoS₂@MoO₃ hybrids also exhibit room-temperature ferromagnetism, revealed by vibrating sample magnetometry (VSM), as a result of the sulfurization process. The MoS₂@MoO₃ gas sensors display a p-type-like response towards NO₂ with a detection limit of 0.15 ppm at a working temperature of 125 °C, as well as superb selectivity and reversibility. This p-type-like sensing behavior is attributed to the heterointerface of MoS₂-MoO₃ where interfacial charge transfer leads to a p-type inversion layer in MoS₂, and is enhanced by magnetic dipole interactions between the paramagnetic NO₂ 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.

Two-dimensional (2D) semiconductors are highly promising candidates for thin-film transistor applications due to their scalability, transferability, atomic thickness, and relatively high carrier mobility. However, a substantial performance gap remains between individual devices based on single-crystalline 2D films and wafer-scale integrated circuits, primarily due to defects introduced during conventional fabrication processes. Here, we report a diamond-assisted electrode transfer technique for the van der Waals integration of wafer-scale prefabricated electrode arrays onto 2D materials, enabling scalable electronics and optoelectronics. Implemented on metal-organic chemical vapor deposition-grown monolayer molybdenum disulfide, this method forms ultraclean metal-semiconductor interfaces, yielding field-effect transistors with excellent ohmic contacts, a low contact resistance of 400 Ω·μm, and a Schottky barrier height of only 9 meV. Furthermore, we demonstrate a scalable transistor array on monolayer molybdenum disulfide with excellent device performance uniformity, achieving an average field-effect mobility of 30 cm² V^-1 s^-1 and an on/off current ratio exceeding 10⁵. Additionally, high photocurrent and responsivity were demonstrated in the array devices, showing their potential for excellent image detection. We further demonstrate the versatility of this technique by fabricating a Schottky diode array through a single-step transfer of asymmetric electrodes─low work function aluminum and high work function gold─onto monolayer tungsten diselenide. This approach provides a clean, effective solution for contact engineering in 2D materials, offering a viable pathway toward wafer-scale, high-performance 2D electronics, optoelectronics, and integrated circuits.