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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]

We report on a voltammetric sensor for caffeine that is based on a glassy carbon electrode modified with Nafion and graphene oxide (GO). It exhibits a good affinity for caffeine (resulting from the presence of Nafion), and excellent electrochemical response (resulting from the pressence of GO) for the oxidation of caffeine. The electrode enables the determination of caffeine in the range from 4.0 × 10 to 8.0 × 10 mol L, with a detection limit of 2.0 × 10 mol L. The sensor displays good stability, reproducibility, and high sensitivity. It was successfully applied to the quantitative determination of caffeine in beverages. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel electrochemically activated nanocomposite, CoS 2 Nanoparticles and MoS 2 Nanosheets decorated poly(diallyldimethylammonium chloride)-functionalized graphene (CoS 2 -MoS 2 -PDDA-GR), was successfully synthesized through a simple and low-cost method. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Electrochemical impedance spectroscopy (EIS) and Cyclic voltammetry (CV) techniques were used to characterize the nanocomposites. Based on the CoS 2 -MoS 2 -PDDA-GR nanocomposite modified glassy carbon electrode, the electrochemical properties of eriocitrin were investigated in detail and a sensitive determinative method was established synchronously. Compared with others, this sensor exhibited larger effective surface area, more reactive site and excellent voltammetric response for eriocitrin. Under optimum conditions by DPV, the oxidation peak currents responded to eriocitrin linearly over a concentration range from 2.0 × 10 −9 to 1.0 × 10 −6 mol L −1 with a detection limit of 6.7 × 10 −10 mol L −1 (S/N = 3). In addition, this fabricated sensor was successfully applied to detect eriocitrin in real samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract A new nanocomposite, zirconium dioxide nanoparticles decorated poly(diallyldimethylammonium chloride)-functionalized graphene (ZrO 2 -PDDA-Gr), was successfully synthesized through a simple and green method. The simultaneous reduction of grapheme oxide (GO) and formation of ZrO 2 to produce the ZrO 2 -PDDA-Gr had been achieved under hydrothermal conditions. The ZrO 2 -PDDA-Gr showed excellent conductivity and strong adsorption ability toward Diosmin and thus was used to be an excellent probe for electrochemical sensing. The electrochemical characteristics of Diosmin were studied in detail and some dynamics parameters of electrode process were also calculated to discuss the reaction mechanism. Under the optimized conditions, a lower detection limit of 2 × 10−9 mol L−1 (S / N = 3) and a wide linear detection range from 5 × 10−9 to 2 × 10−6 mol L−1 were achieved by differential pulse voltammetry (DPV). Additionally, the proposed electroanalytical methodology was applied in fresh lemon leaves and tablets with satisfactory results, showing that fabricated sensor has potential in application. Highlights • ZrO 2 -PDDA-Gr composite was synthesized using a facile, green and effective one-pot hydrothermal route. • ZrO 2 -PDDA-Gr/GCE sensor has high highly sensitive and excellent selectivity for the determination of Diosmin. • This method can be applied in real sample detection with satisfactory result. [ABSTRACT FROM AUTHOR]

This paper described a novel, facile and nonenzymatic electrochemical biosensor to detect hydrogen peroxide (H 2 O 2 ). The sensor was fabricated based on Pd-Pt nanocages and SnO 2 /graphene nanosheets modified electrode (PdPt NCs@SGN/GCE). The electrochemical behavior of PdPt NCs@SGN/GCE exhibited excellent catalytic activity toward H 2 O 2 with fast response, high selectivity, superior sensitivity, low detection limit of 0.3 μM and large linear range from 1 μM to 300 μM. Under these obvious advantages, the constructed biosensor provided to be reliable for determination of H 2 O 2 secreted from human cervical cancer cells (Hela cells). Hence, the proposed biosensor is a promising candidate for detection of H 2 O 2 in situ released from living cells in clinical diagnostics. [ABSTRACT FROM AUTHOR]

In this work, reduced graphene oxide loaded flower-like bismuth subcarbonate composite (Bi 2 O 2 CO 3 -rGO) has been successfully synthesized by a facile hydrothermal method. The prepared Bi 2 O 2 CO 3 -rGO as modification composite was applied to construct voltammetric sensor for the first time. The Bi 2 O 2 CO 3 -rGO modified glassy carbon electrode (Bi 2 O 2 CO 3 -rGO/GCE) exhibited highly sensitive response to urapidil. The electrochemical behavior of urapidil was studied in detail. Under optimum conditions, a lower detection limit (1.5 × 10 −9  mol L −1 ) and wider linear range (5.0 × 10 −9  mol L −1 –4.0 × 10 −6  mol L −1 ) were achieved by the proposed sensor. Finally, the proposed method was applied to the analysis of real sample, and the results showed applicable and reliable. [ABSTRACT FROM AUTHOR]

A novel electrochemical daphnetin sensor was developed by employing a nanocomposite of calcium germanate-graphene (Ca 2 GeO 4 -GR) as an effective electrode material. In this strategy, Ca 2 GeO 4 nanowires could be uniformly distributed on the GR surface with average diameter of about 30–60 nm as exhibited by transmission electron microscopy (TEM). The fabricated sensor (Ca 2 GeO 4 -GR/GCE) exhibited excellent current response towards daphnetin with linear range of 2.0 × 10 − 8 mol L − 1 to 9.0 × 10 − 7 mol L − 1 and detection limit of 6 × 10 − 9 mol L − 1 (S/N = 3). In addition, the sensor also demonstrated strong anti-interference properties in the presence of some metal ions and organic compounds. The proposed method was successfully applied for determination of daphnetin in traditional Chinese medicine (Zushima) and Zushima tablets with satisfactory results. [ABSTRACT FROM AUTHOR]

In this work, poly(sodium p-styrenesulfonate) (PSS)-functionalized graphene supported palladium nanoparticles (Pd) composites were fabricated with simple ultrasonic bath method. The morphology and structure of PSS-GR-Pd composites were characterized using UV–vis absorption spectra, X-ray diffraction and Transmission Electron Microscopy. By combining the merits of the PSS-GR and Pd NPs, a new electrochemical sensor was erected to detect amaranth based on the PSS-GR-Pd nanocomposites. The electrochemical behavior of amaranth was investigated systematically in 0.1 mol L −1 phosphate buffer solution (PBS 2.0). At the optimum parameter, I pa was found to be linearly dependent on the concentrations of amaranth (1×10 −7 –9×10 −6 mol L −1 ). The detection limit was 7 nM (S/N=3) and sensitivity was 5.85 μA μM −1 . Finally, this system was utilized for determining amaranth in soft drink using the standard addition method. [ABSTRACT FROM AUTHOR]

A one-step and facile method using SnCl 2 ·H 2 O as reducing agent to reduce graphene oxide (GO) was performed in the aid of poly(diallyldimethylammonium chloride) solution (PDDA). SnCl 2 ·H 2 O is not only a reducing agent for graphene oxide (GO), but also a precursor of SnO 2 . SnO 2 -PDDA-GR composite was characterized by various surface, structural and electrochemical analysis techniques, such as transmission electron microscopy (TEM), UV spectrum (UV–vis), Infrared Spectrum (IR), X-ray diffraction (XRD), Cyclic voltammograms (CV) and electrochemical impedance (EIS). The SnO 2 -PDDA-GR composite was used to constructed electrochemical sensor (SnO 2 -PDDA-GR/GCE) for the determination of daidzein. Under the optimized experimental condition, it was found that the response of peak current is linear to the concentration of daidzein in the ranges of 2.0×10 −8 −1.0×10 −6 mol L −1 , and the detection limit was estimated to be 6.7×10 −9 mol L −1 (S/N=3). Furthermore, this sensor was successfully applied for the determination of daidzein in traditional Chinese medicine (pueraria lobata) and Daidzein tablets. [ABSTRACT FROM AUTHOR]

The nanocomposites of titanium dioxide nanoparticles decorated poly(diallyldimethylammonium chloride)-functionalized graphene (TiO 2 -PDDA-Gr) were successfully synthesized via a facile and green strategy. The prepared nanocomposites were characterized by X-ray diffraction (XRD), UV–visible spectrophotometry (UV–vis), Fourier Transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). By combining the merits of the PDDA-Gr and TiO 2 NPs, a highly sensitive electrochemical sensor was erected to detect esculetin based on the TiO 2 -PDDA-Gr nanocomposites. Under the optimized conditions, a lower detection limit of 4×10 −9 mol L −1 (S/N=3) and a wide linear detection range from 1×10 −8 to 3.5×10 −6 mol L −1 were achieved by differential pulse voltammetry (DPV). Additionally, the proposed electroanalytical methodology was applied in Chinese herb Viola yedoensis Makino and Cortex Fraxini with satisfactory results, showing that fabricated sensor has potential to be applied. [ABSTRACT FROM AUTHOR]

A simple electrochemical method for the highly sensitive determination of hyperin was established based on poly(diallyldimethylammonium chloride)-functionalized graphene modified electrode (PDDA-Gr/GCE). The nanocomposite was characterized by X-ray diffraction (XRD), ultraviolet/visible spectra (UV–vis), Fourier Transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The electrochemical characteristics of hyperin were studied in detail via cyclic voltammetry (CV), chronocoulometry (CC). Dynamics parameters of electrode process were also calculated to discuss the reaction mechanism. Under the optimized conditions, a lower detection limit of 5 × 10 − 9 mol L − 1 (S/N = 3) and a wide linear detection range from 7 × 10 − 9 to 7 × 10 − 7 mol L − 1 were achieved by the differential pulse voltammetry (DPV). Additionally, this simple, sensitive sensor was proved to be suitable for the determination of hyperin in Chinese herb Hypericum Perforatum with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor was designed and constructed for high-sensitive detection of Taxifolin based on Co 3 S 4 @MoS 2 loaded on reduced graphene oxide (RGO-Co 3 S 4 @MoS 2) as modified materials. It's the first time for Co 3 S 4 @MoS 2 was exploited to constructed electrochemical sensor. Owing to the Co 3 S 4 @MoS 2 providing a huge surface area to enrich more Taxifolin and the excellent electric conductivity of RGO, Taxifolin was detected sensitively with a linear range from 5.0 × 10 −9 to 1.0 × 10−6 mol L−1 and limit of detection down to 1.67 × 10−9 mol L−1 (S/N = 3). In addition, the sensor also demonstrated strong anti-interference properties in the presence of some metal ions and organic compounds. The proposed method was successfully applied for determination of Taxifolin in traditional Chinese medicine in fructus polygoni orientalis with satisfactory results. • RGO-Co 3 S 4 @MoS 2 was fabricated and used to constructed electrochemical sensor. • The RGO-Co 3 S 4 @MoS 2 /GCE exhibits extraordinary electrical properties toward Taxifolin. • The proposed electrochemical sensor shown a satisfactory analytical performance toward Taxifolin. [ABSTRACT FROM AUTHOR]