A novel palladium nanoparticles-polyproline-modified graphite electrode and its application for determination of curcumin

A novel-modified electrode has been developed, by electrodeposition of palladium nanoparticles (PdNps) on polypyroline film-coated (Poly(Pr)) graphite electrode. The modified electrode (PdNps/Poly(Pr)/GE) was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques. SEM proved that the palladium nanoparticles were uniform distributed with an average particle diameter of 20–45 nm. A higher catalytic activity was obtained for curcumin oxidation using this new modified electrode (PdNps/Poly(Pr)/GE). The square wave voltammogram of curcumin in pH 2 phosphate buffer exhibited an anodic peak at 0.504 V. This oxidation peak current was found to be linearly related to curcumin concentrations in the ranges of 5.0?×?10^?9 to 1.0?×?10^?7 M with a detection limit of 1.2?×?10^?9 M. This novel-modified electrode showed excellent sensitivity, compared with the existing reports about determination of curcumin.     

Preparation of PbS Nanoparticles by Phase-Transfer Method and Application to Pb2+-Selective Electrode Based on PVC Membrane

Abstract

A novel approach to prepare homogeneous PbS nanoparticles by phase-transfer method was developed. The preparatory conditions were studied in detail, and the nanoparticles were characterized by transmission electron microscopy (TEM) and UV-vis spectroscopy. Then a novel lead ion-selective electrode of polyvinyl chloride (PVC) membrane based on these lead sulfide nanoparticles was prepared, and the optimum ratio of components in the membrane was determined. The results indicated that the sensor exhibited a wide concentration range of 1.0 × 10^?5 to 1.0 × 10^?2 mol·L^?1. The response time of the electrode was about 10 s, and the optimal pH in which the electrode could be used was from 3.0 to 7.0. Selectivity coefficients indicated that the electrode was selective to the primary ion over the interfering ion. The electrode can be used for at least 3 months without any divergence in potential. It was successfully applied to directly determine lead ions in solution and used as an indicator electrode in potentiometric titration of lead ions with EDTA.     

Electrochemical sensor for ultrasensitive determination of ceftazidime using hollow platinum nanoparticles/reduced graphene oxide/pencil graphite electrode

In this paper, an electrochemical sensor was prepared based on the modification of pencil graphite electrode (PGE) by hollow platinum nanoparticles/reduced graphene oxide (HPtNPs/rGO/PGE) for determination of ceftazidime (CFZ). Initially, rGO was electrodeposited on the electrode surface, and then, hollow platinum nanoparticles were placed on the electrode surface via galvanic displacement reaction of Pt(IV) ions with cobalt nanoparticles (CoNPs) that had electrodeposited on the electrode surface. Several significant parameters controlling the performance of the HPtNPs/rGO/PGE were examined and optimized using central composite design as one optimization methodology. The surface morphology and elemental characterization of the bare PGE, rGO/PGE, CoNPs/rGO/PGE, and HPtNPs/rGO/PGE-modified electrodes was analyzed by field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. The electrochemical activity of CFZ on resulting modified electrode was investigated by cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV). Adsorptive differential pulse voltammetry indicates that peak current increases linearly with respect to increment in CFZ concentration. CFZ was determined in the linear dynamic range of 5.0 × 10^?13 to 1.0 × 10^?9 M, and the detection limit was determined as 2.2 × 10^?13 M using AdDPV under optimized conditions. The results showed that modified electrode has high selectivity and very high sensitivity. The method was used to determine of CFZ in drug injection and plasma samples.     

The Preparation and Application of Bismuth (III) Ion‐Selective Electrode Based on Nanoparticles of Bismuth Sulfide

Abstract

Nanoparticles of bismuth sulfide were prepared in the organic phase and the optimum synthesis conditions for the nanoparticles were studied in detail. Transmission electron microscope (TEM) results indicated that the size distribution of the nanoparticles was proportional with an average diameter of 46.4 nm. A novel bismuth ion‐selective electrode (ISE) was prepared by dispersing the bismuth sulfide nanoparticles in polyvinylchloride (PVC) membrane. The linear range was 1.00×10^?8～1.00×10^?4 mol L^?1 and the detection limit was 8.10×10^?9 mol L^?1. The response of the electrode was fast with quite reasonable reproducibility and stability. It was used to determine bismuth in three kinds of stomach medicines and the results were in good agreement with the flame atomic absorption spectrometry (FAAS) method.     

Voltammetric Determination of Rutin Using a Carbon Composite Electrode Modified with Copper(II)-Resin

Abstract

The preparation and electrochemical characterization of a carbon composite electrode modified with copper(II)-resin as well as its behavior toward rutin were investigated using cyclic and linear sweep voltammetry. The best voltammetric response was observed for a composite composition of 20% (m/m) copper(II)-resin, 0.10 mol L^?1 KNO₃/10^?6 mol L^?1 HNO₃ solution (pH 6.0) as the supporting electrolyte, and a scan rate of 50 mVs^?1. A linear voltammetric response for rutin was obtained in the concentration range from 9.90 × 10^?7 to 8.07 × 10^?6 mol L^?1, with a detection limit of 2.65 × 10^?8 mol L^?1. The proposed electrode was useful for the quality control and routine analysis of rutin in pharmaceutical formulations.     

Electrochemical Sensing of Rutin Using an MCM-41 Modified Electrode

Abstract

MCM-41 was synthesized with uniform pore networks and then used to modify a carbon-paste electrode (CPE). The electrochemical behavior of rutin was investigated. Compared with the bare CPE, the MCM-41–modified CPE remarkably enhances the redox peak currents of rutin, attributed to large surface area, high sorption capacity, and specific mesopores. Based on this, a sensitive and convenient electrochemical method was developed for the analysis of rutin. The linear range is from 2.0 × 10^?8 to 1.0 × 10^?6 mol L^?1, and the limit of detection is 1.5 × 10^?8 mol L^?1. Finally, this method was employed to determine rutin in traditional Chinese medicines.     

The Use of Boron‐Doped Diamond Electrodes for the Amperometric Determination of Flavonoids in a Flow Injection System

Abstract

This paper describes the use of boron‐doped diamond electrode for the amperometric detection and quantification of flavonoids in tea samples using a flow injection system. Flavonoids are phenol derivates widely distributed in fruits, nuts, seeds, flowers, vegetable peels, and beverages; they are known to exhibit high antioxidative activities. After optimization, the experiments were performed at a fixed potential of 0.42 V vs Ag/AgCl with a flow rate of 2.5 ml min^?1 in a Britton‐Robinson buffer at pH 5.0. The results revealed that the peak current increases linearly with rutin concentration in the interval 0.1–2.5×10^?4 mol L^?1 and the detection limit was 7.7×10^?6 mol L^?1. The method was used for the determination of rutin in three different green tea (Camellia sinensis) infusions by the direct addition of 150 µL of untreated sample. The repeatability of current responses for injections of 150 µL rutin was evaluated to be 2.1% (n=20) and the analytical frequency was 100 Hz h^?1. The results were compared with the results obtained by high‐performance liquid chromatrography‐diode ray detector.     

Preconcentration of Rutin at a Poly Glutamic Acid Modified Electrode and its Determination by Square Wave Voltammetry

Abstract

The voltammetric determination of rutin in 0.04 mol l^?1 B‐R buffer (pH 4.0) by square wave voltammograms (+0.41 V vs. Ag/AgCl_(sat.)) at a poly glutamic acid modified glassy carbon electrode was found to be several orders of magnitude lower than that on a bare glassy carbon electrode. Rutin can be preconcentrated on the films of poly glutamic acid and presented linear relationship from concentration of 7×10^?7 to 1×10^?5 mol l^?1 in 0.04 mol l^?1 B‐R buffer pH 4.0. The method was successfully applied to the determination of rutin in pharmaceutical formulation without any pretreatment.     

Chitosan‐Based Glucose Oxidase Electrodes Enhanced by Silver Nanoparticles

Silver nanoparticles enhanced glucose oxidase electrodes were prepared on the basis of chitosan matrix. The enzyme electrodes exhibited high sensitivity and excellent response performance to glucose with a linear range from 1×10^?6 to 8×10^?3 mol · L^?1. And the time reaching the steady‐state amperometric response was less than 5 seconds. The inhibition percentage of this enzyme electrode against copper ions concentration was linear ranging from 1.2×10^?6 to 5×10^?5 mol · L^?1. These properties of enzyme electrodes are probably due to the excellent electron transfer of silver nanoparticles and the orientation of glucose oxidase molecule.     

Electrochemical behavior of adriamycin at an electrode modified with silver nanoparticles and multi-walled carbon nanotubes, and its application

An electrochemical sensor has been constructed for the determination of adriamycin (ADM) that is based on a glassy carbon electrode modified with silver nanoparticles and multi-walled carbon nanotubes with carboxy groups. The modified electrode was characterized by scanning electron microscopy and exhibits a large enhancement of the differential pulse voltammetric response to ADM. Signals are linear with the concentrations of ADM in the range from 8.2?×?10^?9 M to 19.0?×?10^?9 M, with a detection limit of 1.7?×?10^?9 M. The sensor is highly reproducible and exhibits excellent stability. It was to detect calf thymus DNA.     

One-step construction of an electrode modified with electrodeposited Au/SiO2 nanoparticles, and its application to the determination of NADH and ethanol

A new electrode was developed by one-step potentiostatic electrodeposition (at ?2.0 V for 20 s) of Au/SiO₂ nanoparticles on a glassy carbon electrode. The resulting electrode (nano-Au/SiO₂/GCE) was characterized by scanning electronic microscopy, X-ray photoelectron spectroscopy and electrochemical techniques. The electrochemical behavior of dihydronicotinamide adenine dinucleotide (NADH) at the nano-Au/SiO₂/GCE were thoroughly investigated. Compared to the unmodified electrode, the overpotential decreased by about 300 mV, and the current response significantly increased. These changes indicated that the modified electrode showed excellent catalytic activity in the oxidation of NADH. A linear relationship was obtained in the NADH concentration range from 1.0?×?10^?6 to 1.0?×?10^?4 mol?L^?1. In addition, amperometric sensing of ethanol at the nano-Au/SiO₂/GCE in combination with alcohol dehydrogenase and nicotinamide adenine dinucleotide was successfully demonstrated. A wide linear response was also found for ethanol in the range from 5.0?×?10^?5 to 1.0?×?10^?3 mol?L^?1 and 1.0?×?10^?3 to 1.0?×?10^?2 mol?L^?1, respectively. The method was successfully applied to determine ethanol in beer and biological samples.     

Electrocatalysis of Horseradish Peroxidase Immobilized on Cobalt Nanoparticles Modified ITO Electrode

Abstract

It is the first time that Horseradish peroxidase (HRP) was successively immobilized on the magnetic cobalt nanoparticles modified ITO (indium tin oxide) electrode. Morphologies of electrode surface were featured by the field emission‐scanning electron microscope (FSEM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the modified process of electrode. Direct electrochemistry and electrocatalysis of HRP immobilized on nano‐Co/ITO were investigated. The biosensor exhibited high sensitivity, good stability, and excellent electrocatalytic activity to the reduction of H₂O₂. Under the optimized experimental conditions, a calibration curve over 2.0×10^?9～2.0×10^?8 mol l^?1 and 2.0×10^?7～2.0×10^?6 mol l^?1, with a limit of detection of 1.9×10^?9 mol l^?1 was obtained. The apparent Michaelis‐Menten constant (K _M ^app ) for HRP/nano‐Co/ITO electrode was calculated to be 0.79 mmol l^?1, indicating a higher affinity of HRP attached on the modified electrode.     

Preparation of Cu (II) imprinted polymer electrode and its application for potentiometric and voltammetric determination of Cu (II)

The Cu (II) imprinted polymer glassy carbon electrode (GCE/Cu-IP) was prepared by electropolymerization of pyrrole at GCE in the presence of methyl red as a dopant and then imprinting by Cu²⁺ ions. This electrode was applied for potentiometric and voltammetric detection of Cu²⁺ ion. The potentiometric response of the electrode was linear within the Cu²⁺ concentration range of 3.9 × 10^?6 to 5.0 × 10^?2 M with a near-Nernstian slope of 29.0 mV decade^?1 and a detection limit of 5.0 × 10^?7 M. The electrode was also used for preconcentration anodic stripping voltammetry and results exhibited that peak currents for the incorporated copper species were dependent on the metal ion concentration in the range of 1.0 × 10^?8 to 1.0 × 10^?3 M and detection limit was 6.5 × 10^?9 M. Also the selectivity of the prepared electrode was investigated. The imprinted polymer electrode was used for the successful assay of copper in two standard reference material samples.     

MCM/ZrO2 nanoparticles modified electrode for simultaneous and selective voltammetric determination of epinephrine and acetaminophen

A novel MCM/ZrO₂ nanoparticles modified carbon paste electrode (MZ-CPE) was fabricated and used to study the electro oxidation of epinephrine (EP) and acetaminophen (AC) and their mixtures by electrochemical methods. The modified electrode showed electrocatalytic activity toward EP and AC oxidation with a decrease of the overpotential by 173 mV to a less positive potential for EP at the surface of the MZ-CPE and an increase in peak current at pH 7.0. Differential pulse voltammetry peak currents of EP and AC increased linearly with their concentrations in the ranges of 1.0 × 10^?6–2.5 × 10^?3 and 1.0 × 10^?6–2.0 × 10^?3 M, respectively, and the detection limits for EP and AC were 5.0 × 10^?7 and 4.5 × 10^?7 M, respectively.     

Sol-Gel Imprinted Polymers Based Electrochemical Sensor for Paracetamol Recognition and Detection

Molecular imprinting and sol-gel technique were combined to develop a molecular imprinted polymer (MIP) based electrochemical sensor in this work. With the successive modification of multi-walled carbon nanotubes (MWNTs) and gold nanoparticles (GNPs), a modified glassy carbon electrode (GCE) was immersed in a sol-gel solution in the presence of paracetamol (PR) for the electropolymerization to fabricate an imprinted sensor. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were employed to characterize the constructed sensor. The factors for the sensor preparation, the electropolymerization potential range, the monomer concentration, and the scan rate for the sensor preparation were optimized. The sensor displayed an excellent recognition capacity toward PR compared with other analogues. Additionally, the DPV peak current was linear to the PR concentration in the range from 8.0 × 10^?8 to 5.0 × 10^?5 mol/L, with a detection limit of 4.0 × 10^?8 mol/L. The prepared sensor also showed satisfactory reproducibility and regeneration capacity.     

Label-Free Electrochemiluminescent Determination of DNA Using Luminol and Hemin Functionalized Nanoparticles

Luminol and hemin dual-functionalized silica nanoparticles were synthesized using a typical reverse water-in-oil microemulsion protocol. The obtained nanoparticles were further characterized by transmission electron microscopy, scanning electron microscopy, atomic absorption spectrometry, chemiluminescence, and electrochemiluminescence. The results indicated that the luminol and hemin dual-functionalized silica nanoparticles exhibited significantly higher chemiluminescence and electrochemiluminescence intensities than those of luminol functionalized silica nanoparticles due to the catalytic effect of hemin on the chemiluminescence and electrochemiluminescence of luminol. Furthermore, a simple and sensitive label-free electrochemiluminescence DNA biosensor was developed based on the chitosan modified luminol and hemin dual-functionalized silica nanoparticles and a single-stranded DNA probe. The chitosan modified luminol and hemin dual-functionalized silica nanoparticles were immobilized on the surface of an indium-doped tin oxide electrode and the single-stranded DNA probe was immobilized on the surface of the nanoparticles through electrostatic interactions between single-stranded DNA and chitosan, which allowed hybridization with the target DNA sequences. The hybridization events were evaluated by electrochemiluminescence, and only the complementary sequence formed double-stranded DNA with the DNA probe to give strong electrochemiluminescence signals. Finally, the electrochemiluminescence intensity was found to be linearly related to the concentration of the complementary sequence at concentrations from 1.0?×?10^?12 to 1.0?×?10^?6?mol·L^?1 with a detection limit of 5.0?×?10^?13?mol·L^?1.     

A Nonenzymatic Glucose Sensor Based on a Copper Nanoparticle–Zinc Oxide Nanorod Array

A non-enzymatic sensor for glucose based on copper nanoparticles and zinc oxide nanorod array modified fluorine-doped tin oxide conductive glass electrode was constructed by two-step electrodeposition. The electrode was characterized by scanning electron microscopy and X-ray diffraction. The electrochemical behavior of the modified electrodes was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimal conditions, the modified electrode offered a rapid response to glucose in the range from 5 × 10^?6 M to 1.1 × 10^?3 M (R = 0.9975) with a detection limit of 3 × 10^?7 M (S/N = 3) and a sensitivity of 609.8 µA · mM^?1. The preparation and operation of the biosensor was simple, had lower cost, and offered excellent performance due to its high sensitivity, good stability, reproducibility, and selectivity against other substances. The satisfactory results illustrated that it was promising for the determination of glucose in alkaline solutions.     

Detection of rutin at DNA modified carbon paste electrode based on a mixture of ionic liquid and paraffin oil as a binder

A DNA-modified carbon paste electrode (DNA-CPIE) was designed by using a mixture of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and paraffin oil as the binder. The electrochemistry of rutin at the DNA-CPIE was investigated by cyclic voltammetry and differential pulse voltammetry. Rutin exhibits a pair of reversible redox peaks in buffer solutions of pH 3.0, and respective electrochemical parameters are established. Under the optimal conditions, the oxidative peak current is linear with the concentration of rutin in the range from 8?×?10^?9 to 1?×?10^?5 mol L^?1, and the detection limit is 1.3?×?10^?9 mol L^?1 (at S/N?=?3). The electrode exhibits higher sensitivity compared to DNA modified carbon paste electrode without ionic liquid and better selectivity comparing with electrodes without DNA. It also showed good performance, stability, and therefore represents a viable method for the determination of rutin.     

Electrochemical sensing of <Emphasis Type="SmallCaps">D</Emphasis>-penicillamine on modified glassy carbon electrode by using a nanocomposite of gold nanoparticles and reduced graphene oxide

A new electrochemical sensor was developed for determination of D-penicillamine using glassy carbon electrode which had been modified by gold nanoparticles–reduced graphene oxide nanocomposite (AuNPs/RGO/GCE) in aqueous solution. Cyclic voltammetry, transmission electron microscopy and electrochemical impedance spectroscopy were used for characterization of the modified electrode. The results indicated that the kinetic of oxidation reaction of D-penicillamine at the surface of the electrode was controlled by both diffusion and adsorption processes. In 0.1 mol L^?1 phosphate buffer (pH 2.0), the oxidation current increased linearly with concentration of D-penicillamine with a linear range of 5.0 × 10^?6 to 1.1 × 10^?4 mol L^?1 and regression coefficient of R ² = 0.9972. Theoretical detection limit, defined based on 3σ of the blank signal (n = 9) divided by the slope of the linear regression equation, was 3.9 × 10^?6 mol L^?1 D-penicillamine using differential pulse voltammetry. The developed method was successfully applied to the determination of D-penicillamine in pharmaceutical formulation and blood serum samples.     

Ultra-sensitive electrochemical DNA biosensor based on signal amplification using gold nanoparticles modified with molybdenum disulfide,graphene and horseradish peroxidase

We have developed an ultra-sensitive electrochemical DNA biosensor by assembling probe ssDNA on a glassy carbon electrode modified with a composite made from molybdenum disulfide, graphene, chitosan and gold nanoparticles. A thiol-tagged DNA strand coupled to horseradish peroxidase conjugated to AuNP served as a tracer. The nanocomposite on the surface acts as relatively good electrical conductor for accelerating the electron transfer, while the enzyme tagged gold nanoparticles provide signal amplification. Hybridization with the target DNA was studied by measuring the electrochemical signal response of horseradish peroxidase using differential pulse voltammetry. The calibration plot is linear in the 5.0?×?10^?14 and 5.0?×?10^?9 M concentration range, and the limit of detection is 2.2?×?10^?15 M. The biosensor displays high selectivity and can differentiate between single-base mismatched and three-base mismatched sequences of DNA. The approach is deemed to provide a sensitive and reliable tool for highly specific detection of DNA.