Flexible Mo2CTx/MoSe2 Heterostructure Sensors for Ultrasensitive, Room-Temperature Detection of Exhaled H2S in Periodontitis Diagnosis

Oral hydrogen sulfide (H 2 S) level is a critical biomarker for noninvasive periodontitis, making its sensitive and selective detection essential for early diagnosis and real-time monitoring. However, current sensing technologies still face significant limitations in achieving high sensitivity, selectivity, and stability within the complex oral environment. In this study, we report the development of an integrated heterostructure of two-dimensional Mo 2 CT x -modified MoSe 2 (Mo 2 CT x /MoSe 2 composite), tailored for room temperature H 2 S detection in periodontitis diagnosis. The composite synergistically combines the high electrical conductivity and abundant surface defects of Mo 2 CT x with the bandgap tunability and chemical specificity of MoSe 2, yielding an outstanding gas-sensing performance. The optimized Mo 2 CT x /MoSe 2 sensor (0.5 wt % Mo 2 CT x ) demonstrated a high response (Δ R / R 0 = 629% to 10 ppm of H 2 S), an ultralow detection limit (22 ppb), and superior selectivity (3.9–628 times against interfering gases). Moreover, it exhibited excellent long-term stability (<11% signal drift over 40 days) and mechanical robustness, underscoring its suitability for clinical deployment. Density functional theory simulations revealed that enhanced sensing performance arises from strong electronic coupling at the heterointerface, accelerated charge transfer, and efficient molecular activation of H 2 S. Real-time breath analysis confirmed the sensor’s ability to dynamically track trace H 2 S levels, enabling effective discrimination between healthy individuals and periodontitis patients. This work presents a robust and scalable strategy for the early diagnostic screening of periodontitis and lays the groundwork for next-generation wearable or smart diagnostic platforms in oral healthcare.