A study published on July 14 in Matter has developed an external electric-field strategy that dramatically enhances the sensitivity of MXene-based SERS sensors.

The research was led by Prof. YANG Yong and Assoc. Prof. PENG Yusi from the Shanghai Institute of Ceramics (SIC) of the Chinese Academy of Sciences (CAS), with ZHANG Weida from SIC serving as the first author.

Surface-enhanced Raman scattering (SERS) is a powerful technique for detecting trace amounts of molecules, with applications in chemical sensing, environmental monitoring, and biomedical diagnostics. However, many non-metallic SERS substrates still suffer from limited enhancement capability, making it difficult to achieve reliable, order-of-magnitude improvements in sensitivity.

To address this challenge, the researchers applied a stable external electric field to bimetallic Ti₂TaC₂ MXene-based SERS substrates after their fabrication. This active modulation strategy electrically tailors the near-Fermi electronic structure, carrier distribution, and surface plasmon response of the material, simultaneously enhancing both photoelectric charge transfer and electromagnetic enhancement—two key mechanisms that boost SERS signals.

Under the combined effect of 532-nm laser excitation and a 300 V external field, the Ti₂TaC₂ MXene substrates achieved an ultra-low detection limit of 10^-13 M for rhodamine 6G, a common dye molecule. This result represents a three-order-of-magnitude improvement compared with laser excitation alone, highlighting the effectiveness of the electric-field modulation strategy.

According to the researchers, this work establishes an electrically programmable design paradigm for SERS substrates, enabling the charge-transfer and electromagnetic enhancement pathways to be precisely modulated.

More broadly, they added, this strategy could be extended to other quasi-metallic or semiconductor materials, providing a practical route to tunable, high-sensitivity, non-metal SERS sensors and expanding their applications in chemical sensing, environmental monitoring, and biomedical detection.

Schematic illustration of electric-field modulation in a bimetallic MXene SERS substrate and the cooperative enhancement of charge-transfer and plasmonic pathways. (Image by SIC)