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This paper reports a simple and sensitive approach for the determination of troxerutin using a zirconia oxide/graphene doped carbon paste electrode (ZrO2/Gr-CPE). Highly uniform and stable ZrO2 nanoparticles were deposited on Gr sheet via a rapid route. By introducing this nanocomposite into carbon paste electrode, the obtained electrochemical sensor showed sensitive response for troxerutin. Based on this sensor, an accurate sensitive analytical method for troxerutin was established with a linear range from 2 × 10−9 to 3 × 10−7 mol L−1 and a detection limit 6 × 10−10 mol L−1. Meanwhile, the electrochemical properties of troxerutin were investigated in detail. Finally, the proposed method was applied to the analysis of real-life samples with satisfactory results. [ABSTRACT FROM AUTHOR]

A new and sensitive electrochemical sensor for rutin determination was developed based on cetyltrimethylammonium chloride (CTAC) functionalized graphene (Gr) and palladium nanoparticles (Pd) (CTAC-Gr-PdNPs) composite. Rutin displayed remarkably increased electrochemical activity on the CTAC-Gr-PdNPs composite modified electrode due to the synergistic effect of the large surface area and electrocatalytic activity of both Gr and Pd nanoparticles, which offers the feasibility for highly sensitive determination of rutin via electrochemistry. Under the optimal experimental conditions, the oxidation peak current of rutin was proportional to its concentration in the range of 2.0 × 10−8–1.0 × 10−6 mol L−1, and the limit of detection (LOD) was 5 nM (S/N = 3). The developed method was successfully applied to determine rutin in pharmaceuticals with satisfactory recoveries, which shows that the fabricated sensor has potential in pharmaceutical analysis. [ABSTRACT FROM AUTHOR]

A novel, economic, and highly sensitive electrochemical sensor for the determination of trans-resveratrol (RES) was fabricated by electropolymerization of poly(L-lysine) films onto glassy carbon electrode (GCE) surface. The electrochemical behavior of RES in Britton–Robinson buffer solution (pH 2.0) on the poly(L-lysine)/GCE was investigated by cyclic voltammetry and linear sweep voltammetry for the first time. Results showed that the detection range of the proposed sensor to RES was from 0.20 to 12.0 μM with the minimum detectable concentration of 0.06 μM. The reported electrochemical sensor also exhibited high selectivity, good reproducibility, and long-term stability for RES detection. In addition, the proposed method can be employed for the determination of RES in red wines with satisfactory results. The proposed electrochemical strategy presents valuable information related to evaluation of RES levels in real 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]

We report on the voltammetric determination of the flavonoid Baicalein by using a carbon paste electrode that was doped with multi-walled carbon nanotubes. The resulting sensor exhibits excellent redox activity towards Baicalein due to the large surface area and good conductivity of the electrode. Cyclic voltammetry at various scan rates was used to investigate the redox properties of Baicalein. At the optimum conditions, the sensor displays a linear current response to Baicalein in the 0.02-10 μM concentration range, with a limit of detection of 4.2 n M. The method was successfully applied to the determination of Baicalein in spiked human blood serum samples and in a Chinese oral liquid. [Figure not available: see fulltext.] [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]

[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]

The rapid and sensitive determination of antioxidant N-(1,3-dimethylbutyl)-N′-phenyl- p -henylenediamine (6-PPD) in the environment is crucial for early intervention to prevent its adverse effects. Here, a reliable electrochemical sensor based on a N–C mediated γ-Mo 2 N nanocomposite (γ-Mo 2 N@N–C) modified carbon paste electrode (CPE) was developed and applied for selective and sensitive determination of 6-PPD. Benefiting from the superior stability and faster electron diffusion coefficient, the peak current responded to 6-PPD on the sensor linearly over a concentration range from 5 × 10−8 mol L−1 to 1.0 × 10−5 mol L−1 with a detection limit of 1.67 × 10−8 mol L−1 (4.48 ng mL−1). Moreover, the sensor maintained good anti-interference ability in the determination of 6-PPD in soil samples from different regions in Zhengzhou City. Furthermore, the density functional theory (DFT) calculations combined with kinetics analysis proved that the enhanced basicity of the γ-Mo 2 N@N–C facilitated the deprotonation of 6-PPD, with the preferred orientation facet of (200) in γ-Mo 2 N playing a vital role in inducing the dissociation of 6-PPD, thereby improving the sensor's response. Such an electrochemical sensor, with its good stability and superior sensitivity, has the potential to be applied for real-time evaluation and monitoring of environmental pollutants. [Display omitted] • γ-Mo 2 N@N–C modified electrode was firstly developed for quantitative analysis of 6-PPD. • This electrochemical sensor revealed a wide linear range with an ultralow detection limit. • The functions of γ-Mo 2 N@N–C were proved by experiment and DFT calculation. • The sensor maintained good anti-interference ability for the determination of 6-PPD in environment soil. [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]

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]

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]

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]

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 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 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 novel voltammetric sensor was constructed by simple dripping single-walled carbon nanotubes (SWCNTs) on to the glass carbon electrode (GCE) firstly and electro-polymerizing l -Citrulline film subsequently. The resulting poly( l -Citrulline)/SWCNTs/GCE showed a significant voltammetric response to picroside II due to the synergistic effect of SWCNTs and poly( l -Citrulline) film. The first electroanalytical method of picroside II was proposed with detection linear range from 8.0×10 −8 to 5.0×10 −6 mol L −1 and a detection limit of 3×10 −8 mol L −1 .The high sensitivity, selectivity and long-term stability made the sensor suitable for the determination of picroside II. Moreover, based on the systematically investigation and some kinetics parameters calculated in the experimentation, the reaction mechanism of picroside II at the poly( l -Citrulline)/SWCNTs modified GCE was obtained reliably. Lastly, the proposed sensor was used for the determination of picroside II in real sample with satisfactory results. This work promoted the potential applications of amino acid materials and SWCNTs in electro-chemical sensors. [ABSTRACT FROM AUTHOR]

The electro-polymerization of l -Norvaline was investigated for the first time on glassy carbon electrode. The polymeric conditions and mechanism were discussed in detail. The electrochemical behaviors of metribuzin were studied systematically at this sensor and the dynamic parameters of electrode process were calculated. This electrochemical sensor, fabricated simply and very easy surface update, showed good response for metribuzin with a wide linear range from 6.43 × 10 − 3 to 1.07 μg/mL and a low detection limit of 2.14 × 10 − 3 μg/mL (S/N = 3). The proposed method was successfully applied to determine metribuzin in soil sample with satisfactory results. This work promoted the potential applications of amino acid materials in electrochemical sensors. [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 new type of voltammetric sensor, Langmuir-Blodgett (LB) film of multi-walled carbon nanotubes (MWCNTs) perpendicularly modified glassy carbon electrode (GCE), was prepared and applied in determination of methylparaben. Based on the excellent electrochemical property of vertical MWCNTs on the GCE (MWCNTs-LB/GCE), a sensitive voltammetric method for determination of methylparaben was erected with liner range from 1 × 10 −6 mol L −1 to 8 × 10 −5 mol L −1 and detection limit of 4 × 10 −7 mol L −1 . The electrochemical characters of MWCNTs-LB/GCE were investigated in detail and the reaction mechanism of methylparaben was discussed. Meanwhile, cosmetic samples were analyzed using proposed method and the results obtained were well satisfactory. [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 new electrochemical sensor for codeine was fabricated based on composite graphene and Nafion film modified glassy carbon electrode. It was found that the electrochemical response of this sensor was greatly improved and displayed excellent analytical performance for codeine detection, which could be attributed to the high codeine loading capacity on the electrode surface and the outstanding electric conductivity of graphene. Under the optimized conditions at pH 4.0, the peak currents were linear relationship with codeine concentrations in the range of 5×10−8 to 9×10−6 molL−1 and 9×10−6 to 3×10−5 molL−1, using square wave voltammetry with a detection limit of 1.5×10−8 molL−1. The proposed method was successfully applied to the determination of codeine in both urine samples and cough syrup. [ABSTRACT FROM AUTHOR]

Abstract: A novel voltammetric sensor based on graphene–Nafion and poly(L-arginine) was constructed by electrodeposited and simple dipping–drying methods and used for high-sensitive determination of Terbutaline sulfate (TBS). The resulting poly(L-arginine)/graphene–Nafion modified electrode showed a significant voltammetric response to TBS due to the synergistic effect of poly(L-arginine) and graphene–Nafion, in which poly(L-arginine) had electrocatalytic ability for TBS and graphene provided a large specific surface area, excellent electric conductivity and electrocatalytic activity. The sensor gave a good linear range over 4.0×10−8–5.0×10−6 molL−1 with a detection limit of 1.2×10−8 molL−1 towards the determination of TBS. The high sensitivity and selectivity together with the good linear relationship, very easy surface regeneration and good stability at such a modified electrode led us to construct a practical TBS biosensor successfully. This work promoted the potential applications of graphene-based materials in electrochemical sensors. [Copyright &y& Elsevier]

Abstract: In this paper, a multiwall carbon nanotube/Nafion composite modified glassy carbon electrode (MWNT/Nafion/GCE) was used as a voltammetric sensor to determine 8-hydroxyquinoline (8-HQ) in cosmetic. This voltammetric sensor exhibited strong catalytic effect toward the oxidation of 8-HQ and caused an anodic peak at 0.97V in HAc-NaAc buffer solution (0.2M, pH 3.6). Under the optimized condition, the anodic peak current was linear with the concentration of 8-HQ in the range of 2×10−8 M–1.0×10−5 M. The detection limit was 9×10−9 M. The practical application of MWNT/Nafion/GCE was carried out for determining 8-HQ in cosmetic sample with satisfactory results. The electrode reaction mechanism was studied by cyclic voltammetry and UV–vis spectra. [Copyright &y& Elsevier]

Abstract: A highly sensitive electrochemical sensor made of a glassy carbon electrode (GCE) coated with a Langmuir–Blodgett film (LB) containing polyaniline (PAn) doped with p-toluenesulfonic acid (PTSA) (LB/PAn-PTSA/GCE) has been used for the detection of trace concentrations of Ag+. UV–vis absorption spectra indicated that the PAn was doped by PTSA. The surface morphology of the PAn LB film was characterized by atomic force microscopy (AFM). The electrochemical properties of this LB/PAn-PTSA/GCE were studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The LB/PAn-PTSA/GCE was used as a voltammetric sensor for determination of trace Ag+ at pH 5.0 using linear scanning stripping voltammetry. Under the optimal experimental conditions, the stripping current was proportional to the Ag+ concentration over the range from 6.0×10−10 molL−1 to 1.0×10−6 molL−1, with a detection limit of 4.0×10−10 molL−1. The high sensitivity, selectivity, and stability of this LB/PAn-PTSA/GCE also demonstrated its practical utility for simple, rapid and economical determination of Ag+ in water samples. [Copyright &y& Elsevier]

Abstract: The π–A isotherms and UV–vis spectra of the transferred films suggested that the monolayer of p-tert-butylthiacalix[4]arene can coordinate with Hg2+ at the air–water surface. From these observations, a glassy carbon electrode coated with Langmuir–Blodgett film of p-tert-butylthiacalix[4] arene as a new voltammetric sensor is designed for the determination of trace amounts of Hg2+. Compared with bare glassy carbon electrode and modified glassy carbon electrode using direct coating method, the Langmuir–Blodgett film-modified electrode can greatly improve the measuring sensitivity of Hg2+. Under the selected conditions, the Langmuir–Blodgett film-modified electrode in 0.1molL−1 H2SO4 +0.01molL−1 KCl solution shows a linear voltammetric response for Hg2+ in the range of 5.0×10−10 to 1.5×10−7 molL−1, with a detection limit of 2.0×10−10 molL−1. The proposed method was also applied to determine Hg2+ in water samples (tap, lake and river water). In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility and good stability. [Copyright &y& Elsevier]

Here, we developed a homogeneous electrochemical biosensor for the sensitive determination of antibiotic by the CHA reaction and the consecutive adenine mediated probe fixation. The binding of target to the target recognition sequences in the triple-helix DNA can release the trigger. It can initiate the catalytic hairpin assembly (CHA) to generate lots of mimic targets, which were labeled with electroactive substance ferrocene (Fc). Because the generated mimic target has consecutive sequence of adenines (PolyA), they can be self-assembled on the AuNPs modified electrode and finally realize electrochemical detection. Under optimal conditions, this developed biosensor achieved a satisfactory limit of detection of 0.089 nM (S/N = 3) and a linear range from 0.1 nM to 100 nM for sensitive detection of oxytetracycline with good specificity. The whole process is carried out in homogeneous solution, not only realizes signal amplification, but also avoids the complex modification process of electrode surface. Compared with some reported electrochemical sensors, the method is easier to operate and has good precision. [Display omitted] • CHA and signal amplification were triggered by target. • The transformation process between the target and the Fc labeled mimic target was accomplished in homogeneous system. • Mimic targets were self-assembled on the electrode surface by poly adenine to generate electrochemical signal. [ABSTRACT FROM AUTHOR]

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 new voltammetric sensor for simultaneous detection of bisphenol A and bisphenol S with high sensitivity has been constructed based on a three-component composite modified glassy carbon electrode. The three-component composite used herein is composed of AuAgPt ternary alloy nanocrystals (AuAgPt), porous β-cyclodextrin polymer (PCD) and oxide graphene (GO), abbreviated as AuAgPt-PCD-GO. The obtained composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM). The proposed modified electrode showed excellent electrochemical response to bisphenol A and bisphenol S simultaneously. Under optimal experiment conditions, the response linear ranges for bisphenol A and bisphenol S are from 6 nM to 4000 nM and 8 nM–8000 nM with detection limits of 2 nM and 2.67 nM (S/N = 3), respectively. Furthermore, this electroanalytical sensor could also be successfully applied to real sample analysis with satisfactory results. Image 1 • The three-component composite material AuAgPt-PCD-GO was designed to construct a novel electrochemical sensor for simultaneous BPA and BPS assay. • The possible electrochemical oxidation mechanism of BPA and BPS on the modified electrode was deduced. • The proposed sensor can be used for real sample assay 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]