Vacancy-engineered MoO3/TiO2 heterojunctions for high-performance SERS detection of organic contaminants

The construction of semiconductor heterojunctions is a viable approach for enhancing charge separation and improving the SERS performance of semiconductor substrates. In this work, a MoO₃/TiO₂ (MT) heterojunction SERS substrate was developed by integrating oxygen-vacancy-rich molybdenum oxide with titanium dioxide. The optimized MT substrate achieved an ultralow detection limit of 10^–10 M for methylene blue (MB) with an enhancement factor as high as 8.09 × 10⁹. The superior SERS activity of the MT arises from the synergistic contributions of oxygen vacancies and heterojunction coupling. Oxygen vacancies in MoO₃ facilitate strong adsorption of target molecules and provide efficient pathways for photogenerated electron migration, while the band alignment between TiO₂ and MoO₃ promotes effective charge separation. Together, these effects significantly boost the SERS sensitivity, stability, and reliability of the substrate. The proposed MoO₃/TiO₂ system provides a robust and cost-effective platform for ultrasensitive detection of organic pollutants, showing enormous application potential in environmental monitoring and public safety.