Highly sensitive electrochemical sensing of ascorbic acid (vitamin C) using Pd-doped MnO2 supported on carbon quantum dots (Pd-MnO2@CQD) in water and fruit juices.

The Pd-MnO₂ nanoparticles attached to carbon quantum dots nanocomposite were synthesized using the green synthesis and hydrothermal process. Characterization of the as-prepared nanocomposite was intensively performed by FT-IR, powder XRD, XPS, and HR-TEM analysis. The synthesized nanomaterial was further examined for its selective and sensitive ascorbic acid (ASA) sensing using a Pd-MnO₂@CQD modified glassy carbon electrode (GCE). The Pd-MnO₂@CQD nanocomposite exhibits a distinct and improved peak current of ASA when compared to electrodes treated with Pd-MnO₂ and bare GCE. The designed sensor has excellent performance, with a linear range of 10-1500 μM, a low detection limit of 0.14 μM (S/N = 3), a high sensitivity of 1.9671 μAµM^-1 cm^-2. Furthermore, the constructed sensor demonstrates good sensitivity for detecting ASA in a variety of real samples.