Facile design of ultrafine CoFe nanoparticles coupled with nitrogen-doped porous carbon nanosheets for non-enzymatic glucose detection.

Ultrafine CoFe nanoparticles embedded in nitrogen-doped porous carbon nanosheets (denoted as CoFe/NPCSs) are successfully synthesized by utilizing porous plant tissue as a precursor. The morphological, structural, and chemical contents of the CoFe/NPCSs and other control samples are analyzed by X-ray (powder) diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N adsorption-desorption, Raman spectroscopy, inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS) techniques. The glucose oxidation and detection performances of each catalyst are evaluated by using cyclic voltammetry and chronoamperometry. The experimental results demonstrate that the electrocatalytic abilities of the resultant catalysts toward glucose oxidation decrease in the order of CoFe/NPCSs > Co/NPCSs > CoFe/NPCSs > FeC-CoFe/NPCSs > FeC/NPCSs. The experimental results prove that a small number of Fe atoms in CoFe can increase the number of active Co sites. Meanwhile, the ultrafine CoFe nanoparticles uniformly dispersed along the porous carbon nanosheets' surfaces, which further improved the dispersion of the abundant electrochemically available active sites. Due to the synergistic effect of the hierarchical porous structures, high-density active sites and excellent electron conductivity, the optimal CoFe/NPCSs display the best glucose detection efficiency of all the catalysts examined. For instance, the CoFe/NPCSs exhibit large sensitivity values (795.28 µA cm mM between 0.001 and 2.20 mM and 401.98 μA cm mM between 2.20 and 14.00 mM), a rapid response time (2.2 s), a low detection limit (1.0 µM), excellent anti-interference toward electroactive molecules, a perfect reproducibility and a superior long-term stability. The CoFe/NPCSs also exhibit a satisfying efficiency for glucose detection in human serum samples. Finally, our low-cost synthetic strategy can advance research used for designing 3D hierarchical meso/macroporous noble-metal-free catalysts without any tedious steps or templates.