Tunable BTEX Gas Detection At Room Temperature via Composition Engineered MoSe$_{2}$–WSe$_{2}$ Nanocomposites

The detection of hazardous volatile organic compounds, particularly benzene, toluene, ethylbenzene, and xylene (BTEX), is crucial due to their carcinogenic nature and contribution to environmental pollution. Conventional gas sensors often suffer from high operating temperatures, poor sensitivity and selectivity, and slow response times. To address these limitations, composition-tunable MoSe$_{2}$–WSe$_{2}$ heterostructures were synthesized via a facile liquid-phase exfoliation (LPE) technique for room-temperature BTEX sensing applications. A comparative investigation was conducted between two distinct compositional ratios: MoSe$_{2}$:WSe$_{2}$ = 3:1 (n-type dominant) and 1:3 (p-type dominant), to elucidate the role of composition on electrical and sensing behavior. The structural, morphological, and optical properties of the synthesized composites were comprehensively characterized using Raman spectroscopy, FESEM, EDX, XRD, and UV–Vis spectroscopy. The 3:1 sample exhibited dominant MoSe$_{2}$ Raman features with an estimated bandgap of 1.78 eV, whereas the 1:3 sample showed dominant WSe$_{2}$ features with a bandgap of 1.47 eV. Elemental analysis further validated the targeted Mo:W atomic ratios, closely matching the intended 3:1 and 1:3 compositions. Electrical measurements demonstrated a maximum sensor response of 25.74% toward benzene, with a rapid response time of 30 s at a gas concentration of 50 ppm for MoSe$_{2}$–WSe$_{2}$ composite (1:3). This study provides the first detailed report on composition-dependent BTEX sensing performance of MoSe$_{2}$–WSe$_{2}$ heterostructures synthesized via LPE. The findings highlight the critical influence of n-/p-type dominance tuning for achieving gas-specific selectivity, offering promising pathways for the development of next-generation, room-temperature, 2D-material-based gas sensors with tailored sensitivity profiles.