Charge-Transfer Enhanced SERS on MoO₂ Nanoparticles with Ultrahigh Sensitivity and Exceptional Environmental...

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Traditional surface-enhanced Raman spectroscopy (SERS) relies on noble metals, facing limitations like high cost, oxidation, and poor stability.
• Scalable practical applications of SERS are hindered by the drawbacks of noble metal substrates.

Purpose of the Study:

• To synthesize and evaluate molybdenum dioxide (MoO₂) nanoparticles as a high-performance SERS substrate.
• To compare the SERS performance of MoO₂ with molybdenum disulfide (MoS₂) and molybdenum trioxide (MoO₃).
• To elucidate the mechanism behind the enhanced SERS activity of MoO₂.

Main Methods:

• Facile hydrothermal synthesis of monodisperse MoO₂ nanoparticles.
• Systematic evaluation of SERS performance using rhodamine 6G (R6G) and O-safranin (SO) as probe molecules.
• Transient absorption spectroscopy and density functional theory (DFT) calculations to investigate charge transfer (CT) mechanisms.

Main Results:

• MoO₂ nanoparticles demonstrated superior SERS sensitivity and an ultralow detection limit (10⁻¹⁰ M for SO) with a high enhancement factor (3.52 × 10⁷).
• Interfacial charge transfer (CT) was identified as the dominant mechanism for SERS enhancement in MoO₂ systems, supported by quantitative analysis (ρCT > 0.5) and DFT calculations.
• The MoO₂ substrate exhibited remarkable stability under harsh conditions, including acid-alkali corrosion, thermal annealing, and saline immersion.

Conclusions:

• MoO₂ is established as a high-performance SERS substrate offering ultrahigh sensitivity, exceptional stability, and environmental endurance.
• The study clarifies the critical role of interfacial band alignment and CT efficiency in MoO₂-based SERS.
• MoO₂ presents a promising, cost-effective alternative to noble metals for practical sensing applications in complex environments.