Novel heterojunctions associating graphitic carbon nitride g-C₃N₄ and S-doped TiO₂ nanoparticles were successfully designed and prepared via a hydrothermal method and used for photocatalytic degradations. The loading in S-TiO₂ nanoparticles on g-C₃N₄ was varied (5, 10 and 20 wt%), and the photocatalysts were characterized by XRD, FT-IR, solid-state UV-visible diffuse reflectance, photoluminescence, XPS, TEM and SEM. The S-TiO₂ (5%)/g-C₃N₄ catalyst exhibits the highest activity for the photocatalytic degradation of the methylene blue (MB) dye under visible light irradiation. The high photocatalytic performance originates from the enhanced separation and transfer of photogenerated charge carriers. The S-TiO₂ (5%)/g-C₃N₄ photocatalyst is stable and can be reused five times without a sharp drop in activity, indicating its high potential for wastewater remediation.

High-performance hydrogen sulfide (H₂S) sensors are mandatory for many industrial applications. However, the development of H₂S sensors still remains a challenge for researchers. In this work, we report the study of a TiO₂-based conductometric sensor for H₂S monitoring at low concentrations. TiO₂ samples were first synthesized using the sol-gel route, annealed at different temperatures (400 and 600 °C), and thoroughly characterized to evaluate their morphological and microstructural properties. Scanning electronic microscopy, Raman scattering, X-ray diffraction, and FTIR spectroscopy have demonstrated the formation of clusters of pure anatase in the TiO₂ phase. Increasing the calcination temperature to 600 °C enhanced TiO₂ crystallinity and particle size (from 11 nm to 51 nm), accompanied by the transition to the rutile phase and a slight decrease in band gap (3.31 eV for 400 °C to 3.26 eV for 600 °C). Sensing tests demonstrate that TiO₂ annealed at 400 °C displays good performances (sensor response Ra/Rg of ~3.3 at 2.5 ppm and fast response/recovery of 8 and 23 s, respectively) for the detection of H₂S at low concentrations in air.