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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]

A new and sensitive voltammetric sensor for palmatine, based on an electrochemically reduced l-methionine functionalized graphene oxide modified glassy carbon electrode (l-Met-ERGO/GCE), is reported. The electrochemical characteristics of palmatine at the proposed sensor were studied systematically and some dynamic parameters were calculated for the first time. A reasonable reaction mechanism for palmatine on the l-Met-ERGO/GCE electrode was proposed and discussed, and this could be a reference for the pharmacological action of palmatine in clinical study. Under optimized conditions, the peak current had a linear relationship with palmatine concentration in the range of 1 × 10−7 to 5 × 10−5 mol L−1 with a detection limit of 6 × 10−8 mol L−1. Additionally, the proposed method was also used to detect palmatine in human urine samples, medicinal tablets and the Chinese herb Fibraurea recisa Pierre 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 sandwich-type electrochemical aptasensor is described for detecting the carcinoembryonic antigen (CEA) with high sensitivity and accuracy. Two kinds of nanomaterials are used. The first was obtained by modifying gold nanoparticles with reduced graphene oxide and hemin (Hemin-rGO-AuNPs). The second consists of horseradish peroxidase-modified organic-inorganic hybrid nanoflowers linked to gold nanoparticles to obtain an architecture of type HRP-Cu3(PO4)2-HNF-AuNPs). These serve as carriers for two aptamers (apt1 and apt2) against CEA. Simultaneously, they were used to catalyze the precipitation reaction between 4-chloro-1-naphthol(4-CN) and H2O2. A sandwich-type assay linked to enzyme inhibition amplification was established for electrochemical determination of CEA. Under optimal experimental conditions and by using differential pulse voltammetry, the response peak currents (best measured at −0.34 V vs. Ag/AgCl) increases linearly with the logarithm of the CEA concentration in the range between 100 fg mL−1 and 100 ng mL−1. The detection limit is as low as 29 fg mL−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel electrochemical sensor (Ag-Gly-Gr/GCE) for the determination of bergenin was proposed. • The fabrication process of electrochemical sensor is simple and environmentally friendly. • The electrochemical behavior of bergenin was investigated, which is significant for the research of pharmacological properties. Herein, an efficient method for in-situ assembly of silver (Ag) nanoparticles on glycine functionalized graphene (Gly-Gr) has been proposed, which only requires a simple one-step hydrothermal reaction. The microstructure of the material (Ag-Gly-Gr) was characterized by a series of methods, such as FT-IR, XRD, and TEM. For comparison, glycine functionalized graphene (Gly-Gr) was prepared by the same way without adding silver nitrate. The electrochemical sensor (Ag-Gly-Gr/GCE or Gly-Gr/GCE) was prepared by coating the glassy carbon electrode (GCE) surface with dispersive droplets of the related material. The outcomes of the electrochemical impedance test showed that the charge transfer resistance of Ag-Gly-Gr/GCE was less than that of Gly-Gr/GCE and GCE. Compared with the other two sensors, Ag-Gly-Gr/GCE showed a more sensitive response for bergenin. By studying the influence of the pH and sweep rate on the peak potential, the dynamics parameters were discussed to understand the electrochemical reaction mechanism of bergenin. The strategy for quantitative analysis of bergenin was further established at the working potential of 0.8 V (vs SCE). The peak current of bergenin displayed a linear dependence for concentration in 0.01–1 μM with a detection limit of 3.0 nM. Additionally, the analytical availability of Ag-Gly-Gr/GCE was demonstrated by determining bergenin in real-life samples. [ABSTRACT FROM AUTHOR]

Highlights • The Au-Co/GO was synthesized by one-step on site chemical reduction strategy. • Au-Co nanoparticles highly dispersed on GO nanosheets are bimetallic nano-alloys. • The as-prepared Au-Co/GO nanohybrid can act as an improved ECL sensing platform. Abstract Herein, we present the synthesis and electrochemiluminescence (ECL) sensing applications of the Au-Co/GO nanocomposite. Au-Co/GO nanocomposite was prepared for the first time by decorating graphene oxide (GO) with alloy-structured Au-Co bimetallic nanoparticles (BNPs) via one-step on site chemical reduction. The obtained nanocomposite was comprehensively characterized and the results showed that alloy-structured Au-Co nanoparticles (NPs) have an average size of 4 nm and are highly dispersed on GO layers. ECL measurement revealed that the as-synthesized Au-Co/GO nanocomposite displays a synergistic effect of the GO and the Au-Co BNPs on luminol-H 2 O 2 ECL signal. Further immobilization of glucose oxidase (GOD) onto the Au-Co/GO modified electrode afforded a effective ECL glucose sensor which displayed a dynamic range of 1–100 µM with a satisfactory detection limit of 0.18 μM. Furthermore, the developed enzymatic sensors were successfully applied for monitoring glucose in real human samples. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new MOF-5@PDDA-rGO-Ni nanostructure is successfully synthetized for the first time. • MOF-5@PDDA-rGO-Ni/GCE sensor exercises an extraordinary response towards echinacoside as the first detection. • The ratiometric electrochemical sensor devotes a higher accuracy and repeatability than MOF-5@PDDA-rGO-Ni/GCE that affords. • The reliability and stability of the recommendable assay are fairly validated in real sample sliced Cistanche analysis. Abstract In this work, a brand new nanocomplex (denoted as MOF-5@PDDA-rGO-Ni) is elaborately designed and successfully synthesized meaning the in-situ assembly of porous-morphology Zn-based MOFs (MOF-5) onto the as-prepared PDDA-rGO-Ni (PGN for short) nanocomposites. When this nanocomplex contributes to construct the electrochemical sensor (MOF-5@PGN/GCE), it presents a highly-sensitive response towards echinacoside, and the first measurement for echinacoside by electrochemistry accordingly evolves forward. The crystallization processes are investigated by FT-IR instrument and XRD analysis, as well as micro-morphology of modified materials is visible upon SEM and TEM. Adorably, a novel ratiometric sensor was progressively fabricated by encapsulating methylene blue (MB) molecules into cubic MOF-5 framewoks (MB encased MOF-5@PGN/GCE), and apart from assisting in establishing the analysis method with extreme accuracy and favorable practicality, it dose devote a wider linear scale and a lower detection limit than that MOF-5@PGN/GCE has given out. Drawn from the developed calibration curve using differential pulse voltammetry (DPV) technique, the peak intensity ratio (I Ech /I MB) varies linearly with increased echinacoside concentration in the range of 3.0 × 10−8– 1.0 × 10−6 mol L−1 with limit of detection (LOD) reaching 1.0 × 10−8 mol L−1 (S/N = 3). Additionally, the proposed assay method has been employed to detect echinacoside in real sample sliced cistanche with satisfactory results. [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]

The nanocomposite of ruthenium oxide (RuO 2 ) loaded on Poly-(dimethyldiallylammonium chloride) (PDDA) functionalized reduced graphene oxide (RuO 2 -PDDA-rGO) was synthesized based on a one-step method. Based on the RuO 2 -PDDA-rGO modified glassy carbon electrode (GCE), a new electrochemical sensor (RuO 2 -PDDA-rGO/GCE) was fabricated and used in detection of baicalein for the first time. Compared with other reported electrochemical sensors for the detection of baicalein, the prepared RuO 2 -PDDA-rGO/GCE had a wider linear range (2–400 nM) and lower detection limit (0.6 nM, S/N = 3). The other advantages were the excellent repeatability of proposed method and good stability of prepared sensor. [ABSTRACT FROM AUTHOR]

High-density and cross-linked copper-based metal-organic framework (Cu-MOF) sheets were successfully prepared via a simple oriented growth method on a carboxylated graphene-modified electrode surface. Hydrogen peroxide (H 2 O 2 ) was selected as a model molecule to examine the performance of the thin film of Cu-MOF/graphene. The proposed sensor showed an extended linear detection range from 2.00 × 10 −7 to 1.85 × 10 −4 mol L −1 ( R = 0.998), a high sensitivity of 0.792 A (mol L −1 ) −1 , and a low detection limit of 6.7 × 10 −8 mol L −1 , due to the synergistic catalysis from the porous structure and favorable electron transfer mediating function of the electroactive Cu-MOFs and the high conductive property of the graphene. The reduction peak current of H 2 O 2 changed less than 3.7% in the presence of 57-fold high concentrations (2.0 × 10 −4 mol L −1 ) of the potential interfering species. The good selectivity of the prepared modified electrode was acquired by the size exclusion (molecular sieving) for H 2 O 2 because of the proper pore shape and pore size of Cu-MOFs. The feasibility of the assay was verified by test of H 2 O 2 in disinfectant samples. The proposed strategy presents valuable information related to the construction of non-enzymatic electrochemical sensors. [ABSTRACT FROM AUTHOR]

The present paper reported an one-pot synthesis of Co nanoparticles doped amino-graphene nanocomposites (Co-amino-Gr), involving in situ generation of Co nanoparticles (NPs). The simultaneous reduction of graphene oxide (GO) and Co 2+ to produce Co-amino-Gr had been achieved under mild reaction conditions using an environmentally benign reducing agent, glycine. By combining the merits of amino-Gr and the Co NPs, a highly sensitive electrochemical sensor was erected to detect baicalin based on the Co-amino-Gr nanocomposites. Under optimum conditions, the response peak currents were linear related with baicalin concentrations in the range of 1.0×10 −8 –8.0×10 −7 mol L −1 with a lower detection limit of 5.0×10 −9 mol L −1 (S/N=3). Additionally, the proposed method was used to detect baicalin in the medicinal capsules with satisfactory results. [ABSTRACT FROM AUTHOR]

In this paper, a simple, low cost, highly sensitive voltammetric method for determination of tetrahydropalmatine was described, which was based on a new electrochemical sensor, poly (L-glutamic acid) functionalized electrochemical reduction graphene oxide modified glassy carbon electrode. The electrochemical behavior of tetrahydropalmatine was investigated in detail and some dynamic parameters of electrode process were calculated for the first time. Due to large surface area and good conductivity of proposed sensor, a wider linear range (3.0×10 −7 –2.0×10 −5 mol L −1 ) and lower detection limit (1.0×10 −7 mol L −1 ) were achieved for determination of tetrahydropalmatine. Meanwhile, the proposed method was used in determination of tetrahydropalmatine in Rhizoma Corydalis with well results. [ABSTRACT FROM AUTHOR]

A voltammetric sensor for polydatin sensing was simply fabricated by in-situ electrochemically reducing graphene oxide at a glassy carbon electrode. The redox behavior of polydatin was investigated systematically. For the first time, the kinetics parameters of electrode reaction of polydatin were calculated using various electrochemical techniques. Significant electrochemical signal increases were achieved by the excellent conductivity and large surface area of reduced graphene oxide. Thereafter, a highly-sensitive electroanalytical method for polydatin was established with a good linear relationship from 4.0 × 10 − 8 mol L − 1 to 3.5 × 10 − 6 mol L − 1 and a detection limit of 4.0 × 10 − 8 mol L − 1 . In addition, the practical application of present method was demonstrated by determining the concentration of polydatin in real sample with satisfactory result. [ABSTRACT FROM AUTHOR]

A highly sensitive voltammetric sensor, based on reduced graphene oxide on SWCNTs modified glassy carbon electrode (GCE), was constructed and used for sensitive detection of hesperetin. The electrochemical behavior of hesperetin at this sensor was investigated systematically and a novel voltammetric method for determination of hesperetin was proposed. The redox characters of hesperetin was discussed in detail and a reasonable reaction mechanism was proposed also. As the analytical method, the response currents were linear relationship with the hesperetin concentrations in the range of 5.0×10 −8 to 3.0×10 −6 mol L− 1 , with a detection limit of 2.0×10 −8 mol L −1 ( S / N =3). The method was also applied successfully to detect hesperetin in biological samples and Chinese herbal medicine Flos buddlejae with satisfactory results. [ABSTRACT FROM AUTHOR]

A sensitive electrochemical method for determination of daphnetin at reduced graphene oxide (RGO) modified glassy carbon electrode (GCE) was developed. The graphene nanosheets were simply directly deposited onto a GCE surface through cyclic voltammetric reduction of graphene oxide colloidal solution. The redox character of daphnetin at ERGO/GCE was studied systematically and some dynamic parameters were calculated for the first time. The electroanalytical method for determination of daphnetin was established by differential pulse voltammograms (DPV). Under optimum conditions, the response peak currents were linear related with daphnetin concentrations in the range of 5.0 × 10 −8 to 2.0 × 10 −6 mol L −1 with a detection limit of 3.0 × 10 −8 mol L −1 . Therefore, the high sensitivity for daphnetin sensing at the proposed electrode was achieved, which was attributed to the introduced graphene films modified on GCE. Additionally, the proposed method could also be used to detect daphnetin in the medicinal capsules and Chinese medicinal herb Zushima with satisfactory results. [ABSTRACT FROM AUTHOR]

The electrodeposition of reduced graphene oxide (ERGO) film with preferred vertical orientation was fabricated on a glassy carbon electrode by using pulse potential method in a graphene oxide colloidal solution. Using square wave adsorptive stripping voltammetry (SWASV), the ERGO film was applied for the first time, in developing a high-sensitive electrochemical sensor for detection of taxifolin. Compared with bare glassy carbon electrode (GCE), the resulting electrodes (ERGO/GCE) exhibited excellent response toward the redox of taxifolin by significantly enhancing the redox peak currents and decreasing the peak-to-peak separation. Under the selected conditions, the peak currents were linear relationship with taxifolin concentration in the range of 1.0 × 10 −8 –1.0 × 10 −6 mol L −1 , with detection limit of 2.0 × 10 −9 mol L −1 . Besides, the ERGO/GCE also exhibited an excellent selectivity, stability, reproducibility and repeatability. [ABSTRACT FROM AUTHOR]

Abstract: A new and sensitive sensor for morphine, based on electrochemically reduced MWNTs-doped graphene oxide (ER-MWNTs-doped-GO) composite film modified glassy carbon electrode, was reported. Electrochemical impedance spectroscopy and scanning electron microscopy were employed to study the characteristic of the ER-MWNTs-doped-GO film. The electrochemical behaviour of morphine on this sensor was investigated in pH 4.5 phosphate buffer solution by cyclic voltammetry and linear sweep voltammetry. Significant advantages were achieved by combining the excellent conductivity of MWNTs and ER-GO with the film forming properties of GO. And some merits for response towards morphine from this sensor were showed such as wide linear range, fine selectivity and sensitivity, low detect limit and easy surface renewing. The application of the proposed method in analysis of real sample was also evaluated with good performance. [Copyright &y& Elsevier]

A simple, rapid and green method was described for sensitive voltammetric detection of sophoridine based on graphene nanosheets directly deposited onto a glassy carbon electrode (GCE) by pulsed potentiostatic reduction of a graphene oxide (GO) colloidal solution. The resulting electrodes (PP-ERGO/GCE) were characterized by electrochemical methods and scanning electron microscopy. Moreover, the electrochemical behaviors of sophoridine at the modified electrode were investigated in detail by cyclic voltammetry (CV), chronoamperometry (CA) and chronocoulometry (CC). Compared with the bare GCE and the preparation of reduced graphene oxide (RGO) films by potentiostatic method (PM) modified GCE, PP-ERGO/GCE could intensively enhance the oxidation peak currents and decrease the overpotential of sophoridine. Under the selected conditions, the modified electrode showed a linear voltammetric response to sophoridine within the concentration range of 8.0 × 10 −7 ∼ 1.0 × 10 −4 mol L −1 1 , with the detection limit of 2.0 × 10 −7 mol L −1 . And, the method was also applied to detect sophoridine in spiked human urine with wonderful satisfactory. [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]