Ultrasensitive detection of microRNA using a bismuthene-enabled fluorescence quenching biosensor

Bismuthene, a monoelemental two-dimensional material, has shown promise in the biomedical, electronic, and energy fields due to its high carrier mobility and stability at room temperature. However, its use in biosensing applications is restricted due to its undefined quenching mechanism for dye molecules. Herein, we developed a novel ultrathin bismuthene-based sensing platform for microRNA (miRNA)-specific detection that even discriminates single-base mismatches. The detection limit can reach 60 pM. Excitingly, with the fluorescence quenching mechanism of bismuthene, ground state weakly fluorescent charge transfer is determined via femtosecond pump-probe spectroscopy. This finding provides a proof-of-concept platform to (i) fundamentally explore the quenching mechanism of bismuthene and (ii) sensitively detect miRNA molecules for early cancer.