Synergistic Optimization in Ru-Sensitized Mo-WO ₃ Nanosheets for Ultrasensitive ppb-Level H ₂ S Sensing and Real-Time Wireless Oral Health Monitoring

Although metal oxide semiconductors are promising candidates for practical disease diagnosis based on H2S detection, achieving high sensitivity and a low detection limit remains a considerable challenge. In this work, Ru-functionalized Mo-doped WO3 (Ru@Mo-WO3) nanosheets were successfully synthesized via a simple hydrothermal process followed by annealing and chemical reduction. The H2S sensing performances of all WO3-based sensors were systematically investigated. The optimized Ru@Mo-WO3 sensor exhibited a remarkable response of 120 to 5 ppm H2S at the optimal operating temperature, which was approximately 30 times higher than that of pristine WO3. Moreover, the Ru@Mo-WO3 sensor demonstrates short response times, excellent H2S selectivity, and remarkable long-term stability with a low detection limit (7.9 ppb). Comprehensive experimental analyses and density functional theory (DFT) simulations reveal that the significant enhancement in sensing performance originates from the synergistic effects of Mo doping and Ru sensitization. Meanwhile, a wireless gas-detection device based on the as-fabricated Ru@Mo-WO3 gas sensor was developed to achieve real-time monitoring of oral H2S for noninvasive oral hygiene assessment. This study offers a promising strategy for the rational design of high-performance WO3-based H2S sensors.