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This paper demonstrated using polyethylenimine (PEI)-functionalized graphene (Gr) incorporating tin oxide (SnO2) hybrid nanocomposite as a platform for nonenzymatic H2O2 electrochemical sensor. The results of UV-vis spectroscopy and X-ray diffraction (XRD) confirmed the simultaneous formation of tin oxide (SnO2) nanocomposite and reduction of graphene oxide (GO). Transmission electron microscopy (TEM) images showed a uniform distribution of nanometer-sized tin oxide nanoparticles on the grapheme sheets, which could be achieved using stannous chloride (SnCl2) complex instead of tin oxide as precursor. The electrochemical measurements, including cyclic voltammetry (CV) and amperometric performance (I-t), showed that the PEI-functionalized Gr supported SnO2 (SnO2-PEI-Gr) exhibited an excellent electrocatalytic activity toward the H2O2. The corresponding calibration curve of the current response showed a linear detection range of 9×10−6∼1.64×10−3 mol L−1, while the limit of detection was estimated to be 1×10−6 mol L−1. Electrochemical studies indicated that SnO2 and functionalized Gr worked synergistically for the detection of H2O2. [ABSTRACT FROM AUTHOR]

A novel electrochemically treated ZrOCl2 doped carbon paste composite electrode was easily prepared by directly incorporating ZrOCl2 into graphite powder after with an electrochemical treatment for the first time. This sensor showed sensitive voltammetric sensing for daidzein. The surface morphology and electrochemical properties of the electrode were investigated by scanning electron microscopy and cyclic voltammetry. The electrochemical behavior of daidzein was investigated in detail. Under the optimized conditions, the response currents were linearly related to daidzein concentrations in the range of 3×10-8 to 2×10-6 molL-1 with a detection limit of 1×10-8 molL-1 in phosphate buffer solution with pH 2.5. The proposed sensor was also applied to the determination of daidzein in pueraria, pharmaceutical preparations and human uric sample with satisfactory results. [ABSTRACT FROM AUTHOR]