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In this paper, by a simple hydrothermal method vertically aligned ZnO nanorod arrays were grown on the carbon fiber paper (CFP) and then through a facile chemical bath deposition method CuO nanosheets were loaded on ZnO nanorod arrays, following by thermal spraying method, carboxylated carbon nanotubes (CCNTs) were successfully integrated with CuO/ZnO@CFP to form a binder-free CuO/ZnO-CCNT@CFP sensor. The sensor shows enhanced sensing activity for baicalein and luteolin determination due to the improved structural integration and synergism of different electrode material components. Remarkably, the CuO/ZnO-CCNT@CFP sensor showed good linear relationships over wide concentration ranges of 0.03–0.70 µM and 0.70–20 µM for baicalein and 0.03–0.45 µM and 0.45–8.5 µM for luteolin detection, with the detection limits of 1.7 nM for baicalein and 0.5 nM for luteolin, respectively. More importantly, the CuO/ZnO-CCNT@CFP sensor was utilized in the simultaneous determination of baicalein and luteolin, delivering linear ranges of 0.4–14 µM (baicalein) and 0.2–6 µM (luteolin) with the limit of detection of 0.05 µM and 0.03 µM, respectively. In addition, the developed CuO/ZnO-CCNT@CFP electrode was further investigated to detect baicalein and luteolin in traditional herbal medicine samples, showing satisfied results in comparison with analytic results from high performance liquid chromatography. [ABSTRACT FROM AUTHOR]

In this paper, a facial strategy is employed to directly growing ZnO nanorods (ZnONR) on carbon fiber paper (CFP) and functionalizing with silver nanoparticles (AgNP), constructing a structural stable paper-based electrode (AgNP/ZnONR@CFP). This unique AgNP/ZnONR hierarchical nanoarchitecture provides large surface area and an easy substrate penetrable structure facilitating enhanced electrochemical features towards flavonoids oxidation. When the electrode is evaluated as a binder-free sensor for flavonoids detection, three distinct and separate differential pulse voltammetric peaks for luteolin, daidzein, and baicalein are observed, demonstrating the simultaneous and selective detection of these flavonoids possible. The AgNP/ZnONR@CFP sensor demonstrates a remarkable wide linear relationship with low detection limits for luteolin, daidzein, and baicalein detection in a mixed solution. When the sensor is employed to analyze luteolin, daidzein, or baicalein in real extracts from Japanese Honeysuckle, Soybean, and Chrysanthemum morifolium, satisfactory recovery rates (ranging from 96.3 % to 102.5 %) and low relative standard deviation (RSD) values (less than 5.0 %) are obtained. In addition, an assembled sensor device (two-electrode) based on this trimmable AgNP/ZnONR@CFP electrode exhibits remarkable quick response and excellent sensitivity for luteolin, daidzein, or baicalein detection, facilitating real-time and portable detection, highlighting its great potential in batch production of the sensor devices. [Display omitted] • A binder-free electrode is prepared for simultaneous luteolin, daidzein and baicalein detection. • The sensor exhibits high activity with wide linear range and low detection limit. • A two-electrode sensor device is assembled using the AgNP/ZnONR@CFP electrode. • The novel sensor device allows real-time, portable detection and paves the way for mass production. [ABSTRACT FROM AUTHOR]