Dual-Mode Sensor Based on a Single-Atom Cobalt Catalyst for Simultaneous Electrochemical and Colorimetric Detection of Bioactive Small Molecules

The design of single-atom catalysts with dual functions has emerged as a promising strategy for developing high-performance sensing platforms. Herein, we reported a facile host–guest strategy for synthesizing an atomically dispersed Co catalyst (Co–N–C), where Co atoms were uniformly anchored on the N-doped carbon matrix derived from zeolitic imidazolate framework-8. The as-prepared Co–N–C exhibits both excellent electrochemical sensing and peroxidase-like colorimetric activities toward the detection of three important bioactive small molecules, ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrochemical sensor demonstrated ultrahigh sensitivity with detection limits of 4.83, 1.36, and 0.371 μM for AA, DA, and UA, respectively, along with outstanding selectivity against common interferents and stable performance. Meanwhile, the colorimetric method also showed analytical performance with detection limits of 2.24 μM (AA), 3.09 μM (DA), and 2.97 μM (UA). The results indicate that the electronic modulation of Co through precise nitrogen coordination enhances the affinity of Co–Nx for target reactants, thereby promoting adsorption and electron transfer throughout the reaction. This improves catalytic efficiency and selectivity, establishing Co–N–C with dual-catalytic functionality as a promising material for biosensing applications.