Hydrothermally synthesized molybdenum disulfide nanoflakes: structural, electrical, and antenna-based gas sensing characteristics

The growing demand for real-time, low-power, and selective detection of volatile organic compounds (VOCs) at room temperature (RT) presents a significant challenge for environmental monitoring. To address this, we propose a gas sensor platform that integrates molybdenum disulfide (MoS${}_2$)-based nanostructures with an RF antenna transducer exhibiting wireless-like capabilities, offering a promising approach for next-generation sensing technologies. MoS${}_2$ nanostructures were synthesized via a facile hydrothermal method, and the impact of reaction duration on their structural and electrical properties was systematically investigated. The resulting nanostructures exhibited nanoflake (NF) morphology with an interatomic distance of 267 pm. X-ray diffraction confirmed the 2H–MoS${}_2$ phase, with improved crystallinity observed at longer reaction durations. FTIR analysis revealed Mo–S and Mo–O bonding, suggesting the coexistence of oxide phases alongside MoS${}_2$. X-ray photoelectron spectroscopy further confirmed the presence of MoO${}_3$, MoO${}_2$, and MoS${}_2$, with phase ratios influenced by reaction duration. The synthesized materials were applied as sensing layers on dual-functional antenna transducers compatible with wireless sensor networks. The MoS${}_2$-based NF-coated sensor exhibited selective methanol detection in the 1000–8000 ppm range at RT, outperforming responses to other VOCs. Sensors with a higher MoS${}_2$/MoO${}_x$ ratio showed a robust, linear response to methanol, achieving a detection limit of 57.5 ppm with excellent 30-day stability. Principal component analysis confirmed strong selectivity towards methanol, demonstrating effective VOC discrimination. This study highlights the critical role of the hydrothermal phase composition in tuning electrical performance and enhancing VOC detection for wireless sensing platforms based on RF antennas.