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A signal‐off aptasensor was described based on well‐designed aptamer‐Cu3(PO4)2 hybrid nanoflowers&graphene oxide composites (aptamer‐Cu3(PO4)2HNF&GO) as an effective sensing platform and molybdophosphate precipitation as the signaling element. The aptamer, as the biorecognition unit grafted on aptamer‐Cu3(PO4)2HNF&GO by the specificity of streptavidin and biotin, captured the carcinoembryonic antigen (CEA) through specific interaction. The molybdophosphate precipitation were formed by the reaction of the aptamer‐Cu3(PO4)2HNF&GO with molybdate (MoO42−). However, the CEA‐aptamer bioconjugate layer films not only hinder electron transfer on the sensing interface, but also impede the formation of molybdophosphate precipitation, resulting that the current signal significantly decreased. So, a simple aptasensor for CEA was constructed with high sensitivity and signal‐off model. Under optimal experimental conditions using square wave voltammetry (SWV), the response peak currents decreases linearly with the logarithm of CEA concentrations in the range from 10 fg mL−1 to 500 ng mL−1. Also, the feasibility of its applications has also been demonstrated in the analysis of clinical serum samples. [ABSTRACT FROM AUTHOR]

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 activated doped Ta2O5 particles modified carbon paste electrode (EA-Ta2O5-CPE) was prepared and applied for selective and sensitive determination of chrysin. X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) techniques and cyclic voltammetry (CV) were used to characterize the Ta2O5 particles and investigate the electrochemical response of the sensor. Compared with bare CPE, the doped Ta2O5 modified electrode got much more porous by electrochemical treatment and exhibited larger effective surface area, more reactive site and excellent electrochemical catalytic activity toward the oxidation of chrysin. Under optimum conditions by LSV, the oxidation peak currents responded to chrysin linearly over a concentration range from 5.0×10−8 to 7.0×10−6 mol L−1 with a detection limit of 2.0×10−8 mol L−1 (5.08 ng mL−1). The fabricated sensor showed anti-interference ability against the biological common interferents (i.e. baicalein, baicalin) and provided to be reliable for the determination of chrysin in Chinese medicinal herb Oroxylum indicum and chrysin capsules samples with satisfactory results. [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]

A simple and sensitive voltammetric sensor for esculetin, based on electrochemically reduced graphene oxide film modified glassy carbon electrode, was reported for the quantitative determination of esculetin in the Chinese traditional herbal drug Viola yedoensis Makino. Electrochemical impedance spectroscopy and scanning electron microscopy were employed to study the characteristic of the graphene oxide film. The electrochemical behavior of esculetin on this sensor was investigated in pH 3.0 phosphate buffer solution by cyclic voltammetry. Significant advantages were achieved by the excellent conductivity and the high surface-to-volume ratio of electrochemically reduced graphene oxide. A calibration plot of oxidation peak currents versus esculetin concentrations was linear in the range of 4.0 ξ 10-8 mol L-1 to 5.0 ξ 10-6 mol L-1 with a detection limit of 2.0 ξ 10-8 mol L-1. The practical application of the present sensor was demonstrated by determining the concentration of esculetin in real sample with no interference. [ABSTRACT FROM AUTHOR]

A composite LangmuirBlodgett film prepared from DNA and polyaniline was deposited on the surface of a glassy carbon electrode (GCE) to give a new voltammetric sensor for the β2-agonist salbutamol (SAL). Cyclic voltammetry and electrochemical impedance spectroscopy were employed to study the characteristic of the modified electrode. The electrochemistry of SAL at the modified electrode was investigated at pH 6.8 by cyclic voltammetry and differential pulse anodic voltammetry. The oxidation of SAL at this electrode is an adsorption-controlled irreversible process. A sensitive electroanalytical method for determination of SAL was worked out that displays high precision and good reproducibility. The method was applied to quantify SAL in tablets with satisfactory results. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of salvianic acid A sodium (SAS), a main active content in Chinese herbal medicine (CHM), was studied for the first time by cyclic voltammetry (CV). A new electroanalytical method of SAS was erected using differential pulse voltammetric (DPV) technique. In pH 3.3 britton-robinson (B-R) buffer solution, the medicine showed a pair of redox peaks driven by adsorption. The electrode process involved two electrons and two protons transformation with apparent rate constant (ks) of 2.85 s−1 and transfer coefficient (α) of 0.81. Based on understanding the electrochemical process of SAS at the glassy carbon electrode (GCE), analysis of SAS can be realized. The oxidation peak currents showed linear with the concentrations of SAS in the range of 5.45 × 10−8 to 1.09 × 10−5 M. The limit of detection was 5.45 × 10−8 M. The proposed method has high sensitivity, wide linear range, and was successfully applied to quantitative determination of the SAS in Rukuaixiao Tablets. [ABSTRACT FROM AUTHOR]

An ultrastable chemical modified electrode (CME) was fabricated conveniently based on gold film by pulse plating of chloroauric acid on Pt disk electrode. As a novel modifying method of making CME, the CME was characterized by electrochemical impedance spectroscopy (EIS) and used as a voltammetric sensor for Ketamine. This thin gold film modified electrode exhibited excellent electrocatalysis to Ketamine oxidation. Based on this CME, detection of Ketamine by voltammetry was first erected with a fast-response and wide responding linear range. Further experiments demonstrated that this CME has good stability, repeatability and reproducibility. The established method is accurate, reliable, and can be used for the quality control of Ketamine hydrochloride injection. [ABSTRACT FROM AUTHOR]

Two series of conjugated polymers with a carbazole moiety were synthesized by Knovenagel and Wittig condensations. The chemical structure, thermogravimetric, photophysical and electrochemical properties of the polymers were characterized by 1H-NMR, IR, GPC, TG, UV-vis, FL, and CV. The results indicated that PBM is the most thermally stable one and PBP is the most thermally instable one. The absorption and emission properties of the polymers were adjusted by the modification of chemical structures. The quenching effect of cyano group and oxygen atom results in the lower fluorescence quantum efficiency. The fitted emission spectra suggested that the emission spectra of all the polymers come from different vibronic transitions and aggregation emission. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]