High ambipolar mobility fluorinated MXene for ultrasensitive biosensing transistors

Transition metal carbides and nitrides (MXenes) are emerging as transformative materials for bioelectronics. However, the advancement of MXene-based field-effect transistor (FET) biosensors is hindered by the lack of high-quality aqueous-stable materials and the low signal transduction efficiency intrinsic to their metallic nature. To address these issues, we report an ultrasensitive biosensing platform enabled by an in-situ fluorination strategy of MXene. By substituting unstable oxygen-containing terminations with chemically stable fluorine terminations in a mild reaction, we synthesized high-quality fluorinated MXene with the record-breaking ambipolar field-effect mobility (μ_p = 10.42 cm² V^-1 s^-1, μ_n = 30.23 cm² V^-1 s^-1). The highly electronegative fluorinated interface suppresses interfacial electrical double-layer capacitance, boosting signal transduction efficiency. Consequently, the platform achieves the lowest limit of detection (LOD) of 0.26 fg ml^-1 for Mycobacterium tuberculosis antigen MPT64 among MXene FETs up to date, accompanied by a high current response of 35.02% at LOD. Clinical validation across 126 serum samples demonstrated a diagnostic accuracy of 97.6% with a detection time of 38 s, exhibiting the high-performance and reliable biosensing in complex physiological environments.