Electrochemical Nonenzymatic Sensor Based on Cu ₂ O Nanoparticles and Reduced Graphene Oxide for the Sensitive Determination of Glycine and Glucosamine

A nonenzymatic electrochemical sensor was developed for the sensitive detection of glucosamine and glycine using Cu 2 O nanoparticles and reduced graphene oxide–Cu 2 O (RGO–Cu 2 O) nanocomposites synthesized via a green Benedict's method, in which glucose acts as a reducing agent, enabling direct metal–oxide formation without high‐temperature calcination. The morphology, structure, and composition of the materials were characterized by scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Raman spectroscopy, and UV–vis spectroscopy. The electrocatalytic sensing performance of Cu 2 O‐ and RGO–Cu 2 O‐modified carbon paste electrodes were evaluated using cyclic voltammetry and differential pulse voltammetry. Owing to the synergistic interaction between conductive RGO and Cu +1 species, the RGO–Cu 2 O sensor exhibited significantly enhanced electrochemical responses. Under optimized conditions, a linear response for glycine was obtained in the range of 1–15 µM with a limit of detection (LOD) of 0.8 µM, while glucosamine showed an LOD of 0.4 µM with high selectivity. The practical applicability of the sensor was validated in artificial urine and artificial saliva, yielding satisfactory recoveries of 97%–101% for glycine and 94%–102% for glucosamine, with relative standard deviation values below 3.1%, demonstrating excellent accuracy, repeatability, and reliability for real‐sample analysis.