Palladium Nanoparticle-Modified Carbon Spheres @ Molybdenum Disulfide Core-Shell Composite for Electrochemically Detecting Quercetin

Abstract

Quercetin (QR), abundant in plants, is used to treat colitis and gastric ulcer and is also a promising anticancer agent. To quantificationally detect QR, a sensitive electrochemical sensor was fabricated by palladium nanoparticles loaded on carbon sphere @ molybdenum disulfide nanosheet core-shell composites (Cs@MoS2-Pd NPs). The Cs@MoS2-Pd NPs worked to remedy the shortcomings of MoS2 and exhibited good catalytic activity to QR. The oxidation reaction of QR on Cs@MoS2-Pd NPs/GCE involved two electrons and two protons. Furthermore, the molecular surface for electrostatic potential, Laplacian bond order, and Gibbs free energy were computationally simulated to speculate the order and site of the oxidation of QR. The results showed that the 4′ O–H and 3′ O–H broke successively during the oxidation reaction. When the concentration of QR was within 0.5 to 12 μM, the fabricated sensor could achieve linear detection, and the detection limit was 0.02 μM (S/N = 3). In addition, the sensor possessed good selectivity, repeatability, and stability, which has a broad prospect in practical application.

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“…There was a linear relationship between the oxidation peak potential ( E pa ) and the pH, and the linear equation for this was E pa = −0.0595 pH + 0.999 ( R 2 = 0.989). The slope of the linear equation was −0.0595 V per pH, which was close to the Nernst slope (−0.0591 V per pH), 39 so the number of electrons and protons involved in the reaction was inferred to be equal. 40,41…”