Inert-remodeling strategy to build bimetal-confined nitrogen-doped carbon nanozyme for colorimetric-chemiluminescent imaging dual-mode cascade enzyme sensing

The metal-organic frameworks (MOFs)-derived nanozymes in air atmosphere have gained great attention in biosensing fields. Nevertheless, this derivative pattern may result in the destabilization of the MOF framework and the aggregation of active sites, consequently diminishing its catalytic activity. Herein, we reported an inert-remodeling strategy to build bimetal-confined nitrogen-doped carbon nanozyme for dual-mode cascade enzyme biosensing. The strategy was easily achieved by pyrolysis of MOFs (CoNi-ZIF-67 as model) precursor in argon atmosphere, leading to the formation of CoNi bimetallic nanoparticles uniformly confined nitrogen-doped carbon (CoNi–CN) nanozyme. This derivative nanozyme exhibits significantly enhanced peroxidase (POD)-like activity, which is 4 times higher than that of NiCo₂O₄ nanozyme (CoNi-ZIF-67 derivative in air atmosphere) and 54 times higher than that of CoNi-ZIF-67 precursor. The excellent POD-like activity of CoNi–CN nanozyme is ascribed to the following facts: i) integrate structure with uniformly dispersed CoNi bimetal active sites; ii) confinement effect of CoNi bimetal encapsulated in CN architecture. Integrating with glucose oxidase (GOx) to prepare cascade enzyme of CoNi–CN@GOx, colorimetric-chemiluminescent imaging sensor based on CoNi–CN@GOx cascade system was developed for glucose detection. Glucose was assayed in wide linear ranges of 0.08–15 mM (colorimetric) and 0.1–30 mM (CL imaging). This research provides a promising inert-remodeling strategy to construct high-performance nanozyme for dual mode biosensing applications.