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This paper reports a simple approach for the determination of phentolamine mesilate (PM) using a poly(sodium p-styrenesulfonate)-multi-wall carbon nanotube (PSS-MWCNT) modified glassy carbon electrode. PSS-MWCNTs were synthesised via a moderate one-step non-covalent reaction between MWCNTs and PSS. Compared with purified MWCNTs (p-MWCNTs), the introduction of PSS improved the dispersion of MWCNTs and increased the accumulation capability of PM. As a result, the detection sensitivity for PM was greatly enhanced at this voltammetric sensor. The electrochemical properties of PM were first investigated in detail and a reaction mechanism was proposed. Utilizing linear sweep voltammetry, a low detection limit (3.0 × 10 −8  mol L −1 ) and a wide linear range (8.0 × 10 −8  mol L −1 –6.0 × 10 −6  mol L −1 ) were achieved by the proposed sensor. Finally, the proposed method was successfully applied to the analysis of real-life samples. [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]

Emerging contaminant N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine has caused severe threats to ecosystems, necessitating the development of highly sensitive detection methods. Herein, a reliable and ultra-sensitive electrochemical sensor based on a carbon paste electrode modified by hexagonal wurtzite zinc oxide was developed for selective determination and degradation of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. Experimental results demonstrated the successful application of the sensor for detecting N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine in soil samples. The contaminant contents were found to be 1.46–24.68 nmol L−1 in Zhengzhou City and 1.99–11.3 nmol L−1 in Pingdingshan City, respectively, along with a satisfactory recovery rate. Density functional theory calculations revealed that the hexagonal wurtzite zinc oxide crystal significantly decreased the activation energy of catalytic conversion compared to cubic sphalerite, resulting in a notable improvement in sensor response. Cryogenic electron microscopy technique further confirmed that the electrocatalytic degradation product of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine was not toxic N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone. Under optimal analysis conditions, the sensor achieved widely low as well as high linear ranges (0.1–800 nmol L−1 and 0.9–20 μmol L−1) with a low detection limitation (33 pmol L−1), indicating that such a highly sensitive and cost-effective electrochemical sensor has the potential for environmental pollutants monitoring. • HW-ZnO modified electrode was developed for specific recognition of 6-PPD. • Electrocatalytic ability of HW-ZnO and CS-ZnO for 6-PPD was compared. • Cryo-EM result confirmed electrocatalytic degradation of 6-PPD on HW-ZnO/CPE. • The obtained sensor showed wide linear ranges with a low detection limit. [ABSTRACT FROM AUTHOR]

This paper reports on the first electrochemical investigation of glabridin. Under hydrothermal conditions, poly(diallyldimethylammonium chloride) (PDDA) was attached to a graphene (GR) surface via a noncovalent reaction. Moreover, the morphology and structure of PDDA-GR were characterized by transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis. Based on the nanocomposite, a (PDDA-GR/GCE) sensor was prepared, which showed a significant voltammetric response to glabridin. A simple voltammetric method for the investigation of glabridin with a wide concentration range (6.0 × 10−8 mol L−1–6.0 × 10−6 mol L−1) and a low detection limit (2.0 × 10−8 mol L−1) was proposed. The kinetic parameters were calculated, and the reaction mechanism of glabridin was obtained. Additionally, when employed for the analysis of real-life samples, the proposed method showed high accuracy and selectivity. [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, 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]

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]

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]

Chrysin and baicalein are the major flavonoids found in oroxylum indicum, an essential herb in traditional Chinese medicine (TCM). Owing to their similar characteristics and physiochemical property, it is a great challenge to detect both of them simultaneously. In this work, tantalum oxide (Ta 2 O 5 ) particles and chitosan modified carbon paste electrode (Ta 2 O 5 -CTS-CPE) was prepared and characterized by scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectrum(EIS). Under the optimum conditions, the prepared Ta 2 O 5 -CTS-CPE exhibited excellent electrocatalytic activity toward the oxidation of chrysin and baicalein, and it could serve as the sensor for highly sensitive and simultaneous determination both of them. The linear range is 0.08–4.0 μM for both of them, and the detection limits were determined to be 0.03 and 0.05 μM (S/N=3) for chrysin and baicalein, respectively. Furthermore, the proposed electrochemical sensor displayed high sensitivity, excellent stability and got satisfactory results in oroxylum indicum samples analysis. [ABSTRACT FROM AUTHOR]

A new graphene nanocomposite, CeO 2 -poly(diallyldimethylammonium chloride)-graphene (CeO 2 -PDDA-GR), was prepared by an easy and low-cost hydrothermal method. The images of transmission electron microscopy (TEM) showed that well-shaped CeO 2 nanoparticles distributed more uniformly on the GR sheets. Based on the CeO 2 -PDDA-GR composites modified glassy carbon electrode, the electrochemical properties of eriocitrin were investigated in detail and a sensitive determination method was established synchronously. Differential pulse voltammetry (DPV) measurement revealed that the oxidation peak current increased linearly with eriocitrin concentrations in range of 1.0 × 10 − 8 mol L − 1 –1.0 × 10 − 6 mol L − 1 with detection limit of 7.0 × 10 − 10 mol L − 1 (S/N = 3). Moreover, the proposed method was used in determination of eriocitrin in lemon sample with accurate results. [ABSTRACT FROM AUTHOR]

Langmuir–Blodgett (LB) film of C-Undecylcalix[4]resorcinarene (CUCR) as molecular receptor and pretreated glassy carbon electrode (GCE) as enhancer of electron transfer are integrated in the electrochemical sensor system. The new electrochemical sensor possesses the properties of calixarene (high supramolecular recognition and enrichment capability) and pretreated GCE (large surface area and high active sites). At the resulting electrode, the peak current of dopamine (DA) and uric acid (UA) increased dramatically compared with that on the bare GCE and pretreated GCE which due to the synergetic effects of LB film of CUCR and pretreated GCE. Using differential pulse voltammetry, the resulting electrode was applied to develop a high sensitive electrochemical sensor for the simultaneous determination of DA and UA in the presence of ascorbic acid (AA) for the first time. Under the selected conditions, the linear response ranges for DA and UA are 8.0 × 10 −8 to 6.0 × 10 −6 mol L −1 and 4.0 × 10 −7 to 4.0 × 10 −5 mol L −1 , with the detection limits of 2.0 × 10 −8 mol L −1 and 8.0 × 10 −8 mol L −1 , respectively. Besides, the resulting electrode also showed an excellent selectivity, stability and reproducibility. [ABSTRACT FROM AUTHOR]

A simple, inexpensive and highly sensitive voltammetric method for the determination of tectoridin was developed using a poly( l -Arginine) modified electrode. The redox character of tectoridin at proposed electrode was studied systematically and some dynamic parameters were calculated for the first time. A reasonable reaction mechanism of tectoridin on the poly( l -Arginine)/GCE was also dicussed and proposed, which could be a reference for the pharmacological action of tectoridin in clinical study. And the electroanalytical method for determination of tectoridin was established by differential pulse voltammograms (DPV). Under optimum conditions, the response peak currents were linear relationship with tectoridin concentrations in the range of 5.0×10 −8 –2.0×10 −6 mol L −1 with a detection limit of 4.0×10 −8 mol L −1 . Therefore, the high sensitivity for tectoridin sensing at the proposed electrode was achieved, and the proposed method could also be used to detect tectoridin in the Chinese medicinal herb Blackberrylily 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]

Abstract: A simple but highly sensitive and selective electrochemical sensor for the determination of serotonin (5-HT) was presented. Pretreated glassy carbon electrode (GCE) as enhancer of electron transfer and C-undecylcalix[4]resorcinarene film as molecular receptor are integrated in the electrochemical sensor system. The electrochemical behavior of 5-HT at the modified electrode had been investigated in pH 7.0 phosphate buffers solutions by cyclic voltammetry, square wave voltammetry and chronocoulometry. Compared with bare GCE, the proposed integrated sensor showed improved analytical performance characteristics in catalytic oxidation of 5-HT. Under the selective conditions, the modified electrode showed a linear voltammetric response for the 5-HT within a concentration range of 1.0×10−7 to 1.0×10−5 molL−1, and a value of 3.0×10−8 molL−1 was calculated for the detection limit. Besides, due to the difference of potentials, the modified electrode exhibited an excellent immunity from dopamine, epinephrine, ascorbic acid and folic acid interference. [Copyright &y& Elsevier]

Oxidative stress plays an important role in the pathogenesis of many diseases, while the exact mechanism that hydrogen peroxide (H 2 O 2) as one of the most abundant reactive oxygen species (ROS) exerts its influence on oxidative stress remains unclear. We developed a novel turn-on ratiometric electrochemical sensor for the detection of H 2 O 2 in blood samples. The electrochemical probe 5-(1,2-dithiolan-3-yl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)pent-anamide (BA) was designed and synthesized for the selective detection of H 2 O 2 via a one-step amide reaction. Meanwhile, Nile Blue A (NB) was optimized as an internal reference molecule, thus enabling accurate quantification of H 2 O 2 in a complex environment. BA and NB were then co-assembled onto a carbon fiber microelectrode (CFME) coated with Au cones. The oxidation peak current ratio between BA and NB demonstrated good linearity with the logarithm of the H 2 O 2 concentration values ranging from 0.5 μM to 400 μM with a low detection limit of 0.02 μM. The developed sensor showed remarkable selectivity against potential interferences in whole blood samples, especially for ascorbic acid, uric acid, and dopamine. In combination with the unique characteristics of CFME, such as a small size and good biocompatibility, the microsensor was used for rapid analysis of one drop of whole blood sample. This sensor not only creates a new platform for the detection of H 2 O 2 in whole blood samples, but also provides a new design strategy of other ROS analysis for early diagnosis of ROS-related diseases, drug discovery processes, and pathological mechanisms. Image 1 • A novel electrochemical probe molecule for H 2 O 2 were designed and synthesized. • Au nanocones was the first time synthesized for H 2 O 2 detection with high sensitivity. • NB as internal reference improved accuracy, reproducibility and stable. • The sensor was a turn-on system with low background. • Promising for a drop of blood detection by CFME. [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]