F-doped KMn₄(PO₄)₃-based non-enzymatic electrochemical sensor for ascorbic acid and glucose: laboratory sensing and...

The accurate detection of ascorbic acid and glucose demands electrode materials with high conductivity and fast electron transfer. Fluorine doping is an effective strategy to modulate the electronic structure and improve the conductivity of phosphate-based materials. Owing to these benefits, fluorine-doped potassium manganese phosphate (F-doped KMn₄(PO₄)₃) was synthesized by the co-precipitation method and characterized using powder X-ray diffraction (PXRD) analysis, energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The synthesized material was coated onto a nickel foam electrode, and its electrochemical sensing performance towards ascorbic acid and glucose was evaluated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometry. The fabricated electrode exhibited excellent sensing metrics: low detection limits (0.07 µM for ascorbic acid and 0.10 µM for glucose), fast response (2 s for ascorbic acid and 3 s for glucose), high sensitivity (800 µA mM^-1 cm^-2 for ascorbic acid and 1070 µA mM^-1 cm^-2 for glucose), and broad linear ranges (10 µM-14 mM for ascorbic acid and 50 µM-14 mM for glucose), with excellent reproducibility (RSD: 1.70% for ascorbic acid and 2.90% for glucose), repeatability, operational stability, and selectivity. In addition, the practical applicability of the sensor was confirmed through the quantification of ascorbic acid and glucose in real human blood serum samples, achieving maximum recoveries of up to 99% for both analytes.