Bimetallic ZIF-Derived Nitrogenous Porous Carbon Co3O4 as a Peroxidase Mimetic for the Sensitive Detection of L-Cysteine

Nanozymes have attracted considerable attention as a promising class of artificial enzymes with significant development potential in recent years. Herein, a nitrogen-doped hollow porous carbon nanocomposite embedded with Co 3 O 4 nanoparticles (Co 3 O 4 -HPNC) was successfully synthesized through the controlled carbonization and subsequent slow oxidation of bimetallic Co/Zn zeolitic imidazolate frameworks (ZIFs). The Co 3 O 4 -HPNC features a hollow architecture conposed of numerous small nanoparticles, forming a porous flocculent morphology that enhances mass transport efficiency. It exhibited remarkable peroxidase-like activity, catalyzing the oxidation of colorless 3,3 ′ , 5,5 ′ -tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) in the presence of H 2 O 2 . This reaction was driven by the generation of hydroxyl radicals (·OH), as confirmed by fluorescence and electron paramagnetic resonance (EPR) results. Notably, the oxidization process was significantly inhibited by the addition of L-cysteine (L-Cys), leading to a visible fading of the blue color and a corresponding decrease in UV–vis absorbance. Moreover, Co 3 O 4 -HPNC demonstrated good selectivity and strong anti-interference capability toward L-Cys detection. Based on these findings, a simple and effective colorimetric method was developed for quantifying L-Cys with a linear range of 1–50 μM and a detection limit of 0.13 μM (S/N = 3). This Co 3 O 4 -HPNC-based colorimetric platform holds significant potential for applications in biosensors and clinic diagnostics.