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In this work, we first conjugated a short peptide to thrombin binding aptamer (TBA) and bond hemin to the hybrid, effectively rendering hemin/G4-peptide more active over the original hemin/G4, so that a highly sensitive electrochemical thrombin (TB) aptasensor was developed based on it and PtNTs@rGO nanocomposite. It was the first report on the application of hemin/G4-peptide in electrochemical aptasensor. PtNTs@rGO with large surface area served as excellent nanocarrier for high loading of hemin/G4-peptide hybrids, resulting in the formation of hemin/G4-peptide–PtNTs@rGO bioconjugate as the secondary aptamer and further signal enhancement. The specific affinity of aptamer for target TB made the secondary aptamer go into the sensing interface, and then a noticeable current signal was obtained from hemin without additional redox mediators. Due to the collaborative electrocatalysis of hemin/G4-peptide and PtNTs toward H 2 O 2 , which was formed in situ during the process of hemin/G4-peptide-catalyzed oxidation of NADH with dissolved O 2 , the current intensity increased dramatically. Such an electrochemical aptasensing system could be used to detect TB with a linear range of 0.05 pM–60 nM and very lower detection limit of 15 fM. Notably, this method exhibited a higher sensitivity than that of many hemin/G4-based electrochemical strategies for TB detection due to the improvement of the catalytic activity of hemin/G4-peptide. The present works opened a new way for expanding the application of hemin/G4 in biological detection. With the mediator-free, proteinous enzyme-free yet high-sensitivity advantages, this electrochemical aptasensor held great promise for other biomarker detections in clinical diagnostics. [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]

[Display omitted] • NiCoMnS/rGO was synthesized by one-step hydrothermal method. • NiCoMnS/rGO nanocomposite showed good peroxidase-like activity. • NiCoMnS/rGO/GCE can catalyze H 2 O 2 reduction and glucose oxidation. It is attractive to develop non-noble-metal nanomaterials with large surface area and good conductivity as a high-active catalyst electrode for molecular detection in electrochemical sensors. In this work, we successfully fabricated NiCoMnS/rGO by one-step hydrothermal method, which showed good peroxidase-like activity in an acidic environment. The NiCoMnS/rGO modified electrode exhibited excellent enzyme-free electrochemical catalysis performance for hydrogen peroxide (H 2 O 2) reduction in acidic solutions and glucose oxidation in alkaline solutions. For the detection of H 2 O 2 , this electrochemical sensor displayed a wide linear range from 10.0 μM to 7.5 mM with a low limit of detection of 1.1 μM. As for glucose, it also showed a wide linear range from 50.0 μM to 1.3 mM with a low limit of detection of 1.0 μM. Moreover, it had good stability and reproducibility. It was also used for the determination of H 2 O 2 and glucose in real samples. This nanomaterial held great promise as an enzyme-free sensing platform toward H 2 O 2 and glucose detection. [ABSTRACT FROM AUTHOR]

Abstract A new nanocomposite, molybdenum copper selenide (MoCuSe) nanoparticles decorated with reduced graphene oxide (rGO), was successfully prepared by a facile hydrothermal method. The MoCuSe-rGO modified glassy carbon electrode (MoCuSe-rGO/GCE) was fabricated for the first time, which provided a large surface area and exhibited a rapid electron transport rate for the bisphenol A (BPA). The electrochemical behavior of BPA was investigated with various techniques and a new electroanalytical method was established with differential pulse voltammetry. Under optimum conditions, the proposed sensor showed an excellent electrochemical response to BPA with detection limit of 9.0 × 10−10 mol L−1 and wider linear range of 3.0 × 10−9 mol L−1–1.0 × 10−4 mol L−1. Finally, the proposed method was applied to determine BPA in real samples with satisfactory results. This work might provide a new thought for the development of electrochemical sensors with hybrid materials. Graphical abstract Unlabelled Image Highlights • A new nanocomposite, MoCuSe-rGO, was successfully prepared by a facile hydrothermal method. • The MoCuSe-rGO was applied to construct voltammetric sensor for the first time. • A new voltammetric method displayed a wider detection linear range and lower detection limit for BPA detection. [ABSTRACT FROM AUTHOR]

A novel high-sensitive electrochemical sensor with glassy carbon electrode (GCE) as support for hyperin determination is successfully designed and constructed, and the well-shaped nano-meter modified material is synthesized via a one-step and facile route. Functionalized with surfactant sodium dodecyl sulfate (SDS), Single-Walled Carbon Nanotubes (SWCNTs) are synchronously grafted with ZrO 2 nanoparticles to develop into the as-prepared nano-composite (ZrO 2 -SDS-SWCNTs). Compared to the previous reports related with hyperin detection, the linear range gets wider and detection limit (LOD) becomes lower with the aid of this novel nano-composite modified glassy carbon electrode (ZrO 2 -SDS-SWCNTs/GCE). The crystalline phases and functionalization of the preparation process has been investigated by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) instrument analysis, respectively, and the micro-morphology of related modified materials is also visibly characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). In addition, electrochemical properties of the modified materials are comparably explored by means of impedance spectroscopy (EIS) and cyclic voltammograms (CV). According to the established calibration curve under optimized condition, the peak current (Differential pulse voltammetry (DPV) signal) keeps a linear relationship with hyperin concentration in the ranges of 1.0 × 10 −9 − 3.0 × 10 −7 mol L −1 , meanwhile detection limit reaches as low as 5 × 10 −10 mol L −1 (S/N = 3). As for practical applications, the proposed sensor has also worked well on sensitive hyperin determination in real species Abelmoschus manihot. [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]

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]