Cobalt Single-Atom/Nanoparticle Dual Sites on Unzipped Carbon Nanotubes for Electrolyte-Switchable Glucose and Uric Acid Sensing

Non-enzymatic multi-analyte sensing using a single electrode remains challenging owing to the distinct electrochemical environments and catalytic pathways required for different biomarkers. Here, we report an electrolyte-regulated bifunctional electrocatalyst comprising atomically dispersed Co-N/O sites and Co/CoO nanoparticles anchored on nitrogen-doped unzipped carbon nanotubes (SA/NP Co@N-UzCNT) for selective glucose and uric acid (UA) detection. Partial unzipping of the outer CNT walls generates edge-rich graphene nanoribbons while preserving the electrically conductive inner CNT framework, providing abundant N-coordination sites for stabilizing structurally distinct Co motifs. Under alkaline conditions, nanoparticle-derived Co sites are electrochemically converted into catalytically active CoOOH species that promote glucose oxidation, whereas atomically dispersed Co-N sites dominate UA oxidation under neutral conditions, demonstrating electrolyte-dependent catalytic selectivity between the two Co configurations. Switching the electrolyte environment alters the dominant catalytic site, enabling selective detection of glucose and UA using a single-electrode architecture. The resulting sensor achieves sensitivities of 65.18 µA mM−1 cm−2 for glucose in the concentration range of 1–8 mM and 337.5 µA mM−1 cm−2 within the concentration range of 5–500 µM for UA. Practical applicability is demonstrated using a screen-printed electrode strip, which retains approximately 89% of its initial glucose response after 15 days. This work demonstrates that single-atom/nanoparticle coexistence can serve as a functional catalytic architecture for electrolyte-regulated non-enzymatic multi-analyte sensing.