Co-N/C-900 metal-organic framework-derived nanozyme as a H₂O₂-free oxidase mimic for the colorimetric sensing of l-cysteine

Nanozymes have attracted considerable attention as a new type of promising artificial enzyme in recent years. Here, an oxidase-like cobalt-nitrogen-carbon (Co-N/C-900) nanozyme with well-regulated metal atom spatial distribution has been derived from Co-Zn bimetal zeolitic imidazolate framework precursors and used to develop a facile colorimetric sensing method for l-cysteine. With the aid of Co-N/C-900, the colorless 3,3′,5,5′-Tetramethylbenzidine (TMB) was oxidized to blue oxidized TMB in the absence of H2O2. However, the oxidation was inhibited after the addition of l-cysteine, and the blue color faded to colorless. Thus, Co-N/C-900 exhibited quite good oxidase-like activity with high catalytic efficiency. Therefore, a facile and efficient colorimetric method to sensitively determine l-cysteine with a low detection limit of 33 nM (S/N = 3) has been developed. Furthermore, favorable selectivity and anti-interference ability towards the determination of l-cysteine based on this approach have also been achieved. It is believed that this colorimetric method for the detection of l-cysteine based on Co-N/C-900 will show potential applications in bioscience and bioengineering.