Molybdenum Boride MBene with an Ultraclean Surface for Stable and Portable Detection of Environment Toxins

The inherently poor chemical stability and sensitivity of two-dimensional MXene materials pose significant challenges for their application in non-noble metal surface enhanced Raman scattering (SERS) under harsh conditions. Herein, a novel unfunctionalized Mo_4/3B₂ MBene with an ultraclean surface is reported as a stable, ultrasensitive SERS substrate for portable detection of environment toxins. The Mo_4/3B₂ MBene enables the detection of R6G down to 10^-11 M with an SPF of 4.23 × 10⁵, surpassing most MXene substrates, and its SERS mechanism is mainly attributed to the synergistic effects of enhanced charge transfer efficiency promoted by the ultraclean surface and vacancy modulated photon induced charge transfer resonance. Moreover, it exhibits excellent long-term SERS enhanced stability, which can maintain 86%, 75%, and 61% of its initial SERS performance after 45 days of storage at room temperature and 14 days of storage at low (-26 °C) and high (100 °C) temperatures. Notably, a portable Raman system based on Mo_4/3B₂ demonstrates ultrasensitive detection of the ricin A chain in real river water, achieving a concentration limit of 0.01 μg/mL and 97.8% accuracy assisted by the developed Transformer model. This work offers new insights for designing stable and sensitive MBene-based SERS substrates for field-deployable sensing in security and public health scenarios.