Two-dimensional mesoporous nitrogen-rich carbon nanosheets loaded with CeO2 nanoclusters as nanozymes for the electrochemical detection of superoxide anions in HepG2 cells

Two-dimensional (2D) porous carbon-based composite nanosheets loaded with metal oxide nanoclusters are expected to be promising electrocatalysts for high-performance electrochemical sensors . However, for this complicated composite material, strict reaction conditions and complex synthesis steps limit its general application in electrochemical detection . Here we present a facile method to fabricate 2D mesoporous nitrogen-rich carbon nanosheets loaded with CeO 2 nanoclusters (2D-mNC@CeO 2 ), for fabricating superoxide anions (O 2 •− ) electrochemical sensor. The method is based on block copolymers self-assembly and the affinity of polydopamine to metal ions to obtain organic-inorganic hybrid, which can be directly converted into 2D-mNC@CeO 2 through carbonization strategy without structural deterioration . Characterizations demonstrate that the 2D-mNC@CeO 2 owned the 2D N-doped carbon structure with an interlinked hierarchical mesoporous and the uniformly dispersed CeO 2 nanoclusters on the surface. Benefitted from the unique structure, the 2D-mNC@CeO 2 shortens electron transfer distance, enhances mass transfer efficiency, exposes numerous active sites, and obtain a high Ce 3+ /Ce 4+ ratio for improving electrocatalytic performance. The 2D-mNC@CeO 2 /SPCEs sensors for O 2 •− detection has a detection limit of 0.179 μM (S/N = 3) and sensitivity of 401.4 μA cm -2 mM -1 . The sensors can be applied to capture electrochemical signals of O 2 •− released from HepG2 cells, demonstrating the application potential of the sensors to monitor O 2 •− in biological fields.