FeC-Assisted Single Atomic Fe Sites for Sensitive Electrochemical Biosensing.

The rational construction of advanced sensing platforms to sensitively detect HO produced by living cells is one of the challenges in both physiological and pathological fields. Owing to the extraordinary catalytic performances and similar metal coordination to natural metalloenzymes, single atomic site catalysts (SASCs) with intrinsic peroxidase (POD)-like activity have shown great promise for HO detection. However, there still exists an obvious gap between them and natural enzymes because of the great challenge in rationally modulating the electronic and geometrical structures of central atoms. Note that the deliberate modulation of the metal-support interaction may give rise to the promising catalytic activity. In this work, an extremely sensitive electrochemical HO biosensor based on single atomic Fe sites coupled with carbon-encapsulated FeC crystals (FeC@C/Fe-N-C) is proposed. Compared with the conventional Fe SASCs (Fe-N-C), FeC@C/Fe-N-C exhibits superior POD-like activity and electrochemical HO sensing performance with a high sensitivity of 1225 μA/mM·cm, fast response within 2 s, and a low detection limit of 0.26 μM. Significantly, sensitive monitoring of HO released from living cells is also achieved. Moreover, the density functional theory calculations reveal that the incorporated FeC nanocrystals donate electrons to single atomic Fe sites, endowing them with improved activation ability of HO and further enhancing the overall activity. This work provides a new design of synergistically enhanced single atomic sites for electrochemical sensing applications.