Film-modified Glassy Carbon Electrode Research Articles

Simultaneous Determination of Serotonin and Tryptamine Using Polyglutamic Acid-Silver Nanoparticles Composite Film Modified Glassy Carbon Electrode

Serotonin (ST), chemically 5-hydroxy tryptamine, is a neurotransmitter which mediates a series of central and peripheral functions in the human body and has a crucial role in gastrointestinal and psychiatric disorders. Tryptamine (Tryp) is also a neurotransmitter, mainly found in protein-rich foods, beverages and other fermented foods. The accumulation of higher concentrations of Tryp is harmful to human health. So, it is important to determine both ST and Tryp in our body. A polyglutamic acid (pGlu)-Silver Nanoparticles (AgNPs) composite film modified Glassy Carbon Electrode (pGlu-AgNPs/GCE) has been developed for the simultaneous determination of ST and Tryp. The incorporation of AgNPs with pGlu makes the sensor more efficient and reliable for the voltammetric sensing of ST and Tryp. Experimental parameters were optimised and, the sensor showed a linear concentration range for the determination of ST and Tryp from 1.00 × 10–5 M to 7.00 × 10–7 M and 1.00 × 10–5 M to 9.00 × 10–7 M, respectively. The electrooxidation of ST at pGlu-AgNPs/GCE was found to be diffusion controlled, whereas adsorption controlled electrooxidation was found for Tryp. The applicability of the sensor in determining ST and Tryp has been checked in artificial physiological fluids.

A novel electrochemical sensor based on phosphate-stabilized poly-caffeic acid film in combination with graphene nanosheets for sensitive determination of nitro-aromatic energetic materials

This work offers a novel approach and sensor electrode for electrocatalytic reduction of nitro-aromatic explosives (NAEs). This sensor was created by combining electrochemically reduced graphene nanosheets (GNSs) −through cyclic voltammetric reduction of a graphene oxide colloidal solution− with phosphate-stabilized poly-caffeic acid (pCAF) film-modified glassy carbon electrode (GCE). The poly-caffeic acid−modified nonconductive electrode was stabilized with a H2PO4-/HPO42− phosphate buffer at pH 7 and made conductive. The novel electrode, called phosphate stabilized-GC/GNSs/pCAF, was characterized by electrochemical methods and scanning electron microscopy (SEM). The sensor exhibited high performance for trinitrotoluene (TNT) detection with a linear response between 50 and 500 μg L− 1 and a detection limit of 6 μg L−1. In addition to TNT, precise determinations of NAEs such as 2,4-dinitrotoluene (2,4-DNT), tetryl (2,4,6-trinitrophenyl methyl nitramine), trinitro phenol (TNP or picric acid; PA), 2,4-dinitrophenol (2,4-DNP), and 4-amino dinitrotoluene (4A-DNT, an aerobic bacterial degradation product of TNT) were made using the developed sensor electrode and DPV technique. Simultaneous quantification of TNT and DNT was performed with the aid of a computational technique known as multiple linear regression (MLR). The optimized electrode was resistant to interference effects. Satisfactory results on real samples were obtained by applying the modified electrode to the determination of TNT, tetryl, and TNP in contaminated soil. The validation of the proposed method was made against a literature LC-MS/MS method. A statistical comparison of the obtained results was provided using F- and Student's t-tests.

Intelligent recognition of CTCs from gallbladder cancer by ultrasensitive electrochemical cytosensor and diagnosis of chemotherapeutic resistance

Gallbladder carcinoma (GBC) is one of most aggressive and lethal malignancies. Early diagnosis of GBC is crucial for determining appropriate treatment and improving chances of cure. Chemotherapy represents the main therapeutic regimen for unresectable GBC patients to inhibit tumor growth & metastasis. But, chemoresistance is the major cause of GBC recurrence. Thus, there is an urgent need to explore potentially non-invasive and point-of-care approaches to screen GBC and monitor their chemoresistance. Herein, we established an electrochemical cytosensor to specifically detect circulating tumor cells (CTCs) and their chemoresistance. Trilayer of CdSe/ZnS quantum dots (QDs) were cladded upon SiO2 nanoparticles (NPs), forming Tri-QDs/PEI@SiO2 electrochemical probes. Upon conjugation of anti-ENPP1, the electrochemical probes were able to specifically label captured CTCs from GBC. The detection of CTCs and chemoresistance were realized by square wave anodic stripping voltammetric (SWASV) responses to anodic stripping current of Cd 2+ ion when cadmium in electrochemical probes was dissolved and eventually electrodeposited on bismuth film-modified glassy carbon electrode (BFE). Taking use of this cytosensor, one ensured the screening of GBC and limit of detection for CTCs approaches to ～10 cells/mL. Furthermore, by monitoring phenotypic changes of CTCs after drug treatment, the diagnosis of chemoresistance was achieved by our cytosensor.

Poly L- methionine/Electrochemically Reduced Graphene Oxide Composite Film Modified Glassy Carbon Electrode for the Simultaneous Determination of 5-hydroxyindole Acetic Acid and Tyrosine

An effective electrochemical sensor based on “poly L- methionine/Electrochemically Reduced Graphene Oxide Composite Film Modified Glassy Carbon Electrode (poly(L-Met)/ERGO/GCE))” has been developed for the individual and simultaneous determination of 5-hydroxyindole acetic acid (5-HIAA) and tyrosine (Tyr). In clinical point of view, simultaneous determination of these analytes is very important and a sensor for the same is not reported yet. This sensor offers sensitive, reproducible and selective determination of 5-HIAA and Tyr. Experimental parameters for the effective determination of the analytes were optimized. Under optimized conditions, quantification of 5-HIAA is possible within the range 1.0 × 10−5 M to 8.0 × 10−7 M and for Tyr in two ranges, 1.0 × 10−5 M to 5.0 × 10−6 M and 7.0 × 10−5 M to 2.0 × 10−5 M. The limit of detection and limit of quantification obtained for 5-HIAA using poly(L-Met)/ERGO/GCE are 5.0 × 10−7 M and 8.0 × 10−7 M respectively, and for Tyr, 1.0 × 10−6 M and 5.0 × 10−6 M respectively. The sensor was successfully applied for the determination of both 5-HIAA and Tyr in artificial urine and blood serum samples.

Determination of nitrite in food based on its sensitizing effect on cathodic electrochemiluminescence of conductive PTH-DPP films

Herein, a novel strategy for electrochemiluminescence (ECL) detection of nitrite based on its sensitization effect on cathode ECL emission of 3,6-di(2-thienyl)-2,5-dihydropyrrolo [3,4-c] pyrrole-1,4-dione (TH-DPP) polymeric films (PTH-DPP) was formulated, by means of a one-step electropolymerization of TH-DPP with a short time on the glassy carbon electrode (GCE). It was shown that the PTH-DPP film-modified GCE exhibited a strong ECL response when S2O82− was used as a co-reactant. The ECL emission could be greatly enhanced by PTH-DPP with nitrite in a K2S2O8/PBS solution system and occurred at a relatively lower potential in comparison with traditional cathode ECL emitter, leading to high sensitivity and good selectivity. The ECL sensor exhibits excellent linear relationship in the ranges of 0.3 to 100 μM and 100 to 1000 μM for nitrite detection, with an outstanding detection limit of 0.08 μM (S/N = 3). The ECL sensor provides an impressive outcome for the detection of practical samples.

Construction of polythiophene-derivative films as a novel electrochemical sensor for highly sensitive detection of nitrite.

Herein, a novel, convenient, and highly selective electrochemical sensor for determination of nitrite based on a polythiophene-derivative film-modified glassy carbon electrode (GCE) was established. In this work, 2,5-di-thiophen-3-yl-thiazolo[5,4-d]thiazole (DTT), a novel thiophene derivative, was synthesized and used to form an original and excellent polymer film (PolyDTTF) on GCE through one-step electropolymerization for the first time. The modified electrodes were characterized by electron microscopy (SEM), Fourier transform infra-red spectroscopy (FT-IR), UV-visible spectra, Raman spectroscopy, and electrochemical technologies, in which the electrochemical sensor based on PolyDTTF was successfully constructed and demonstrated a significant electrocatalytic effect on nitrite. The influence of pH value, electrodeposition scanning times, scanning speed, and potential on the electrochemical behavior of nitrite were investigated in detail. Furthermore, the nitrite sensor exhibits excellent responses proportional to nitrite concentrations (R2 = 0.9972) over a concentration range of 5.5 × 10-9 ~ 3.5 × 10-5M with a detection limit (LOD) of 2nM, and has extremely good anti-interference ability for nitrite detection. This proposed sensor can be used to detect nitrite in actual samples, opening the possibility for applications in the food industry and environmental analysis.

Copper Film Modified Glassy Carbon Electrode and Copper Film with Carbon Nanotubes Modified Screen-Printed Electrode for the Cd(II) Determination.

A copper film modified glassy carbon electrode (CuF/GCE) and a novel copper film with carbon nanotubes modified screen-printed electrode (CuF/CN/SPE) for anodic stripping voltammetric measurement of ultratrace levels of Cd(II) are presented. During the development of the research procedure, several main parameters were investigated and optimized. The optimal electroanalytical performance of the working electrodes was achieved in electrolyte 0.1 M HCl and 2 × 10−4 M Cu(II). The copper film modified glassy carbon electrode exhibited operation in the presence of dissolved oxygen with a calculated limit of detection of 1.7 × 10−10 M and 210 s accumulation time, repeatability with RSD of 4.2% (n = 5). In the case of copper film with carbon nanotubes modified screen-printed electrode limit of detection amounted 1.3 × 10−10 M for accumulation time of 210 s and with RSD of 4.5% (n = 5). The calibration curve has a linear range in the tested concentration of 5 × 10−10–5 × 10−7 M (r = 0.999) for CuF/GCE and 3 × 10−10–3 × 10−7 M (r = 0.999) for CuF/CN/SPE with 210 s accumulation time in both cases. The used electrodes enable trace determination of cadmium in different environmental water samples containing organic matrix. The validation of the proposed procedures was carried out through analysis certified reference materials: TM-25.5, SPS-SW1, and SPS-WW1.

Electrochemical Biosensor Based on HRP/Ti3C2/Nafion Film for Determination of Hydrogen Peroxide in Serum Samples of Patients with Acute Myocardial Infarction.

Hydrogen peroxide (H2O2) has been reported to mediate a variety of physiological and pathological processes in living systems. In this work, a biosensor for determination of H2O2 was prepared by using an HRP/Ti3C2/Nafion film-modified glassy carbon electrode (GCE). Ti3C2 nanosheets with remarkable conductivity and high specific surface area were chosen as carriers for HRP. Moreover, this biosensor modified with HRP has a specific catalytic effect on H2O2. The difference in peak current could reflect the quantitative change of H2O2. The linear range of the biosensor is 5-8000 μM, and the detection limit is 1 μM (S/N = 3). This biosensor was used to detect H2O2 in clinical serum samples of normal controls and patients with acute myocardial infarction (AMI) before and after percutaneous coronary intervention (PCI). The results showed that the difference between normal controls and patients is significant (P < 0.05), as well as the difference for patients before and after PCI (P < 0.01), but no significant difference existed between postoperative patients and normal controls. This biosensor has the advantages of simple preparation, high sensitivity, and quick detection, showing potential application in clinical diagnosis.

Electrochemically imprinted self-doped polyaniline as highly sensitive voltammetric sensor for determination of bismuth in water, wastewater, and pharmaceutical samples

A novel electrochemically imprinted self-doped polyaniline (SDPAn) film-modified glassy carbon electrode (GCE) for bismuth ion (Bi3+) determination was prepared here based on copolymerization of polyaniline with metanilic acid, GCE/P(An-co-MA). Firstly, prepared SDPAn was characterized by using solid-state UV–visible, SEM, and EDXA techniques. Then, the GCE/P(An-co-MA) electrode was templated by several consecutive reduction/oxidation potential steps in Bi3+ solution for improving its selectivity to Bi3+ ions. Affecting parameters on detection signal like MA concentration, pH, and time in polymerization step and preconcentration potential and incubation pH in preconcentration step have been optimized by means of experimental design. The differential pulse anodic striping voltammetric signal of the GCE/P(An-co-MA) in optimized conditions was recorded and a linear relation ship from 1.0 × 10−9 to 1.0 × 10−4 M of Bi3+, R2 as 0.9960, with detection limit as 0.48 nM Bi3+, and RSD as 1.49% was obtained. This sensor was successfully applied for voltammetric determination of Bi3+ ions in water, wastewater, and pharmaceutical samples.

Square-wave adsorptive stripping voltammetric approaches at two in situ modified electrodes as first analytical methods for the quantitative determination of a new anticancer drug candidate

The two adsorptive stripping voltammetric approaches for detection and quantitative determination of diethyl (2E)-2-{(2E)-[1-(4-methylphenyl)imidazolidin-2-ylidene]hydrazinylidene}butanedioate (DIB)—a novel molecule of medical importance—using two sensitive sensors based on modified glassy carbon electrodes as reusable sensors, were developed for the first time. The proposed electrochemical methods are based on adsorptive/reductive behaviour of DIB at two modified carbonic electrodes: a bismuth film-modified glassy carbon electrode (BiF/GCE) and a lead film-modified glassy carbon electrode (PbF/GCE). The electron gain mechanism for the electrochemical reduction of DIB on both developed sensors was proposed for the first time. To achieve the highest sensitivity in adsorptive stripping determinations, various experimental variables (e.g. the composition and pH of the supporting electrolytes, deposition conditions of bismuth and lead films, concentrations of plating solutions, accumulation times and potentials of DIB, etc.) were extensively examined. The comparison of validation parameters obtained during the determination of DIB at two sensors was presented. The excellent linear correlation was found between the monitored adsorptive stripping voltammetric peak current and the DIB concentration in the range of 15–600 μg L−1 at an accumulation time of 30 s (with LOD = 4.2 μg L−1 and LOQ = 14.0 μg L−1) using the BiF/GCE as a sensor. Furthermore, the excellent linear relationship was confirmed between the monitored adsorptive stripping voltammetric peak current and the DIB concentration in the range of 9–900 μg L−1 at an accumulation time of 10 s (with better LOD = 1.5 μg L−1 and LOQ = 5.0 μg L−1), employing the PbF/GCE as a sensor. The two optimized adsorptive stripping voltammetric approaches—as facile, sensitive, reliable and inexpensive—were successfully used as first methods for the quantitative analysis of a novel anticancer agent (DIB) in its pure pharmaceutically acceptable form. However, the practical applicability of square-wave adsorptive stripping voltammetric determination of the electroactive DIB molecule at a PbF/GCE, as the modified electrode of higher sensitivity, was presented after its successful solid phase extraction from a real serum sample.

CARBON NANOTUBES&amp;#8211;IONIC LIQUID GEL. CHARACTERIZATION AND APPLICATION TO PSEUDOEPHEDRINE AND CHLORPHENIRAMINE DETERMINATION IN PHARMACEUTICALS

A multi-walled carbon nanotube (MWCNT)-ionic liquid (IL) film-modified glassy carbon electrode (GCE) was constructed for the determination of pseudo­ephedrine (PE) and chlorpheniramine (CP) by differential pulse voltammetry (DPV). The MWCNT-IL film has shown an obvious electrocatalytic activity towards oxidation of PE and CP, since it increases the electroactive area, facilitates the electron transfer and significantly enhances the oxidation peak current of both. Also a synergistic effect between MWCNT and IL was detected; it improves the conductivity, resulting in a better response, thus the modified electrode presented higher sensitivity. Under the optimum conditions, the oxidation peak currents were linearly proportional to the concentration in the range from 40.3 to 161.3 μg/mL for PE and from 0.39 μg/mL to 27.4 μg/mL for CP. Detection limits were 32.4 μg/mL with 180 s accumulation for PE and 0.11 μg/mL with 240 s accumulation for CP. Finally, the proposed sensitive and simple electrochemical method was successfully applied to PE and CP determination in a pharmaceutical formulation, and recoveries were acceptable.

Fabrication of PEI-Fc/SGO multilayer films modified electrode through LBL assembly technique for the detection of dopamine

In this work, a sensor for the detection of dopamine (DA) based on electroactive polymer (PEI-Fc)/sulfonic acid-functionalized graphene oxide (SGO) multilayer film-modified glassy carbon electrode (GCE) through layer-by-layer (LBL) method was fabricated. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy revealed the successful functionalization of GO into SGO with negatively charged sulfonic groups. The obtained PEI-Fc/SGO multilayer films were characterized using scanning electron microscopy (SEM) and ultravioletvisible spectrometer (UV-Vis). Cyclic voltammetric studies demonstrated that the modified electrode presented enhanced electrocatalytic performance towards DA in terms of peak currents compared with bare GCE. The choronoamperometric results indicated that the modified electrode exhibited a wide linear range from 1 to 695 μM with a low detection limit of 0.255 μM towards the detection of DA. Besides, the modified electrode exhibited good selectivity, excellent reproducibility, and high stability of at least 1 month.

Voltammetric determination of vanillin in commercial food products using overoxidized poly(pyrrole) film-modified glassy carbon electrodes

Voltammetric determination of vanillin in commercial food products using overoxidized poly(pyrrole) film-modified glassy carbon electrodes

Interference Effects of Cu(II) and Pb(II) on the Stripping Voltammetric Detection of Cd(II): Improvement in the Detection Precision and Interference Correction

In this study, a novel analytical method for the quantitative determination of Cd(II) under the interference of Pb(II) and Cu(II) via a combination of square-wave anodic stripping voltammetry (SWASV) and chemometric methods is proposed. In addition, this study focuses on the analysis of interference in the electroanalysis of Pb(II), Cd(II) and Cu(II) with an in situ bismuth film-modified glassy carbon electrode (Bi/GCE). In the presence of these mutual interferences, the chemometric methods considerably improved the resolution of the voltammetric technique. The chemometric methods, namely, a back-propagation artificial neural network (BP-ANN), a particle swarm optimization-support vector machine (PSO-SVM) and a ternary linear regression equation (TLRE), were used to determine the Cd(II) concentration under the interference of Cu(II) and Pb(II). The prediction performances of the different chemometric methods were verified in terms of their root mean square errors (RMSEs), average relative errors (AREs), mean absolute errors (MAEs), and correlation coefficients (R2). The results indicate that the BP-ANN and PSO-SVM had higher prediction accuracies than the monadic linear regression equation (MLRE) and TLRE. Finally, the proposed method was used to determine the Cd(II) concentration in soil samples, with satisfactory results.

Electrochemical synthesis of graphene/polypyrrole nanotube composites for multifunctional applications

A conducting composite film has been fabricated using graphene oxide (GO) and pre-prepared one-dimensional polypyrrole (PPy) nanotube as the feedstock. GO with various oxygen-containing groups effectively promotes the dispersion of well-defined PPy nanotubes to obtain a stable and homogeneous GO/PPy complex solution. By a one-step and large-scale electrochemical reduction, the graphene/PPy nanotube composite film is successfully synthesized. Graphene nanosheets uniformly cover the surface of the electrode and PPy nanotubes act as spacers and conducting bridges to prevent the restacking of graphene sheets and connect the isolated graphene nanosheets. Electrochemical experiments indicate that the composite films have high performances due to the combination of the advantages of graphene and PPy nanotube. When the graphene/PPy nanotube composite is directly used as the supercapacitor electrode, it shows high specific capacitance and good cycling stability during 1000 charge/discharge cycles. Furthermore, an electrochemical biosensor is constructed through the entrapment of horseradish peroxidase (HRP) onto the composite film-modified glassy carbon electrode (GCE). The immobilized HRP showed high catalytic activity for the reduction of H2O2, which may be ascribed to high conductivity, great surface coverage, and good biocompatibility of the prepared graphene/PPy nanotube composite film. This method may be extended to prepare other conducting composite films with structure-controllable nanostructures in large scale for the application of electrochemical fields.

Low dimensional Bi2Te3-graphene oxide hybrid film-modified electrodes for ultra-sensitive stripping voltammetric detection of Pb(II) and Cd(II)

Inorganic layered materials, also known as “graphene-like” inorganic analogues, have emerged as a new and versatile source of nanomaterials. Due to their thickness-dependent physical properties they have drawn an enormous scientific interest as regards their exfoliation and the potential use of the exfoliated two-dimensional crystals to attractive new applications in various industrial and technological sectors. This work reports for the first time, the use of low dimensional Bi2Te3-graphene oxide (GO) hybrid films as electrode’s modifiers for the ultra-sensitive determination of Pb(II) and Cd(II) ions in the sub microgram-per-liter level by using anodic stripping voltammetry. Bulk Bi2Te3 was exfoliated by applying an easy-to-perform, sonication-assisted liquid exfoliation method in a triple blend of 1+3+4v/v 1-cyclohexyl-2-pyrrolidone, acetone and water. The resulting dispersion showed a slow sedimentation rate and exhibited an extended electrode surface coverage with respect to the bulk material, as it was documented by electrochemical impedance spectroscopy comparative measurements. To achieve the desired adherence of exfoliated Bi2Te3 films at electrode surface, Be2Te3 dispersion was mixed with an aqueous dispersion of GO, which was used as supporting material. Compared with the bulk Bi2Te3/GO hybrid film-modified glassy carbon electrodes (GCEs), exfoliated Bi2Te3/GO hybrid film-modified GCEs exhibited remarkably enhanced detection capabilities and limits of detection (S/N 3) as low as 0.1μgL−1 Pb and 0.2μgL−1 Cd. This work provides new data on the facile preparation of stable dispersions of Bi2Te3 and Bi2Te3/GO composites, which can be easily cast into films offering highly sensitive sensors. In addition, it offers new insights in the applicability of exfoliated Bi2Te3 in electroanalysis and can trigger the development of advanced sensors based on other inorganic layered materials.

Simultaneous determination of trace Cd(II) and Pb(II) based on Bi/Nafion/reduced graphene oxide-gold nanoparticle nanocomposite film-modified glassy carbon electrode by one-step electrodeposition

In this paper, a simple and controllable one-step electrodeposition method was used to fabricate a novel reduced graphene oxide-gold nanoparticles (RGO-GNPs) nanocomposite film onto the surface of bare glass carbon electrode (GCE), and then, Nafion was modified onto the film to prepare an electrochemical sensor for simultaneous detection of trace Cd(II) and Pb(II) in square-wave anodic stripping voltammetry (SWASV) with situ plating bismuth film. The morphologies and electrochemistry properties of the modified electrode were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), cyclic voltammetry (CV), and SWASV. It was found that the formed RGO-GNPs nanocomposite film on the GCE surface could remarkably facilitate the electron transfer and enlarge the specific surface area of the electrode. While the Nafion film could effectively increase the adhesion and stability of RGO-GNPs nanocomposite layer, enhance cation-exchange capacity, and prevent the macromolecule in real samples absorbing on the surface of electrode. The Bi/Nafion/RGO-GNPs/GCE demonstrated a highly linear behavior in the simultaneous detection of Cd(II) and Pb(II) in the concentration range of 1.0 to 90 μg/L with detection limits of 0.08 and 0.12 μg/L (S/N = 3), respectively. Finally, The developed electrode was further applied to the determination of Cd(II) and Pb(II) in soil samples with satisfactory results.

Fabrication of an electrochemical immunosensor for α-fetoprotein based on a poly-L-lysine-single-walled carbon nanotubes/Prussian blue composite film interface

Single-walled carbon nanotubes functionalized with poly-L-lysine (PLL-SWCNTs) were successfully prepared and were used as a biocompatible platform to immobilize α-fetoprotein antibody (anti-AFP) which was labeled with horseradish peroxidase (HRP). Then, anti-AFP-HRP/PLL-SWCNT nanocomposites were coated onto a Prussian blue (PB) film-modified glassy carbon electrode surface. Glutaraldehyde was used to further stabilize the biosensing interface through a cross-linking step. All unspecific sites were blocked by bovine serum albumin to fabricate a novel electrochemical immunosensor for α-fetoprotein determination. The immunosensor was characterized by voltammetry and electrochemical impedance spectroscopy. Based on the catalytic current response of H2O2, the experimental conditions for α-fetoprotein determination were optimized. Under optimal conditions, the current response was linearly related to α-fetoprotein concentration in the range of 0.05∼10.0 and 10.0∼50.0 ng/mL with a detection limit of 0.011 ng/mL. The immunosensor was successfully used for the determination of α-fetoprotein in human blood plasma. The results were satisfied with that obtained with ELISA, demonstrating a good accuracy of the immunosensor.

Electrochemical non-enzyme sensor for detecting clenbuterol (CLB) based on MoS2-Au-PEI-hemin layered nanocomposites

Clenbuterol (CLB), a kind of β2-adrenergic agonists, could disrupt cardiovascular and central nervous system. In this work, a new electrochemical non-enzyme sensor for detecting Clenbuterol (CLB) was fabricated based on MoS2-Au-PEI-hemin layered nanocomposites. The two-dimensional (2-D) MoS2 nanosheets were first in-situ assembled with Au nanoparticles, and polyethylenimine (PEI), then hemin molecules were immobilized onto the MoS2-Au-PEI film-modified glassy carbon electrode (GCE) via amide bond. Scanning electron microscopy (SEM) and Zeta potential measurements were employed to characterize the MoS2-based nanomaterials. Cyclic voltammetry (CV) was used to investigate electrochemical activity of the immobilized hemin on the modified electrode. Upon the optimum conditions, the proposed electrochemical sensor showed an excellent response for CLB including a wide linear ranging from 10ng/mL to 2μg/mL and a detection limit (LOD) of 1.92ng/mL CLB (S/N=3) with favorable reproducibility and stability. Furthermore, this presented method could be feasible for determining CLB in the real pork samples.

Voltammetric determination of trace heavy metals using an electrochemically deposited graphene/bismuth nanocomposite film-modified glassy carbon electrode

A novel electrochemically deposited graphene (EG)/bismuth (Bi) nanocomposite film-modified glassy carbon electrode (GCE) was prepared through successive electrodeposition of exfoliated graphene oxide (GO) and in situ plating bismuth film. Experimental variables, including deposition potential and bismuth concentration, were carefully optimized to determine trace zinc, cadmium, and lead ions by using the EG/Bi electrode as an electrochemical-sensing platform. The linear calibration curves ranged from 1 to 100μgL−1 for Zn2+, Cd2+, and Pb2+. The detection limits were 1.80μgL−1 for Zn2+, 0.18μgL−1 for Cd2+, and 0.11μgL−1 for Pb2+ (S/N=3). The EG/Bi nanocomposite film electrode was successfully applied to the analysis of trace metals in real environments.