J Hazard Mater 2026 Feb 15;504:141365. doi: 10.1016/j.jhazmat.2026.141365.

Strategic engineering of D-band center and oxygen vacancy in In6WO12-xSx for ultrahigh signal-to-noise ratio gas sensing at parts-per-billion level NO2.

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Metal oxide semiconductor sensors often suffer from high intrinsic resistance and sluggish response kinetics at low temperature, resulting in an ultralow signal-to-noise ratio that severely limits their applicability in wearable devices. To overcome these limitations, a vapor-phase sulfur diffusion method is employed to transform sea-urchin-like In6WO12 microspheres into tubular In6WO12-xSx structures, providing a large surface area and efficient gas diffusion pathways. The In6WO12-xSx sensor exhibits a dramatic resistance reduction at 100 ℃, from 813632 Ω for pristine In6WO12 to 7872 Ω, effectively overcoming the high resistance limitation. This improvement originates from the synergistic effect of intrinsic In3 + -W6+ cations, which facilitate efficient charge transport, while sulfur doping narrows the bandgap and introduces abundant oxygen vacancies, collectively leading to a pronounced reduction in resistance. Additionally, the In6WO12-xSx sensor demonstrates exceptional gas sensing performance at 100 °C, including a 1712-fold enhancement in signal-to-noise ratio compared to the pristine sample for detecting 1000 ppb NO2, a fast response time (27 s), an ultralow detection limit (0.56 ppb), low cross-sensitivity (selectivity coefficient >5), and outstanding long-term stability over 70 days. These enhanced low-temperature sensing performances are attributed to the increased oxygen vacancy and an elevated d-band center, all of which synergistically improve NO2 adsorption and reaction kinetics.

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