Electric field-engineered bimetallic MXene for ultra-sensitive SERS sensors

Advances in ultra-sensitive surface-enhanced Raman scattering (SERS) substrates and SERS enhancement strategies are the two fundamental pillars for the development of SERS technology. However, broadly applicable strategies that reproducibly achieve order-of-magnitude improvements in SERS sensitivity remain scarce. Herein, we propose an electric-field modulation strategy to simultaneously stimulate photo-electric-induced charge transfer (PEICT) and surface-plasmon enhancement (PESP). This strategy increases the density of states near the E F and induces an upward shift of E F , thereby lowering inter-band transition barriers and promoting surface electron localization. Guided by this strategy, a series of bimetallic MXene SERS-active substrates are theoretically predicted and experimentally reported for the first time. Under cooperative excitation with a 532-nm laser and a 300-V field, Ti 2 TaC 2 achieves a limit of detection (LOD) of 10 −13 M and a SERS performance factor (SPF) of 2.3 × 10 5 , a three-orders-of-magnitude gain over laser-only excitation. This strategy provides a broadly applicable route to substantially enhance SERS sensitivity in non-metallic substrates.