Developing electroactive materials with superior sensitivity, selectivity, and so on is an important issue for target ions detection. Hierarchically heterostructured nanomaterials represent a kind of promising active materials for electrochemical sensors due to the synthetic effect between different components and the high surface area. Herein, heterostructured UIO-66-NH 2 /CNTs nanocomposites have been successfully synthesized via the solvothermal method and investigated for the detection of Pb 2+ ions. The SEM, TEM, XRD and FTIR collectively confirmed that the UIO-66-NH 2 was successfully loaded on the surface of the CNTs. The specific surface areas of the UIO-66-NH 2 /CNTs are 4–7 times higher than that of activated CNTs and more mesoporous structures appear in composite materials. The electrochemical impedance spectroscopy measurements showed that the concentration of CNTs could influence the electron mobility and the UIO-66-NH 2 /CNTs-15 exhibits the lowest charge transfer resistance and the highest capacitive property. The cyclic voltammetry study towards K 3 [Fe(CN) 6 ] further demonstrated that the CNTs can improve the conductivity of the composites especially for the UIO-66-NH 2 /CNTs-15, which was conducive to the sensing behavior confirmed by follow-up performance experiments. Under the optimized condition, UIO-66-NH 2 /CNTs-15 exhibits the best sensing performance towards Pb 2+ . Correspondingly, a high sensitivity of 1.64 μA (μmol/L) −1 and a low detection limitation of 0.206 μmol/L (S/N = 3) are achieved. Meanwhile, a wide detection range, excellent selectivity, repeatability, and stability are also obtained. The recovery experiment by standard addition method is also carried out and a satisfactory result has been attained indicating a promising sensor for practical application.
Quercetin (Qu), a naturally occurring flavonoid, is critically involved in sustaining human physiological health. Therefore, it is imperative to rationally design a proficient electrochemical sensor capable of sensing Qu. Herein, a ternary nanocomposite composed of Keggin-type polyoxometalate (PMo 12 ), carbon nanotubes (CNTs), and zirconium-based MOF (UiO-66-NH 2 ) was successfully fabricated to develop a sensitive electrochemical sensor for Qu determination. Benefiting from the synergistic integration of diverse components, the high conductivity of CNTs, good electrocatalytic performance of PMo 12 , and favorable adsorption capacity of UiO-66-NH 2 jointly facilitated the adsorption and electron transfer process of Qu at the electrode interface. The constructed sensor showed a broad linear detection range of 10–160 μM, high detection sensitivity reaching 0.226 μA·μM −1 , and a detection limit as low as 0.486 μM (S/N = 3) at the optimized working conditions. Besides, the developed sensor exhibited outstanding selectivity, stability, reproducibility, and repeatability. By determining the Qu content in Flos Sophorae Immaturus samples, we further confirmed the actual application capability of the constructed sensor. Satisfactory recoveries of 97.01%–101.08% were obtained, which strongly validated the reliability and accuracy of the proposed electrode for practical Qu analysis.
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