Electrocatalysis and detection of nitrite on a polyaniline‐Cu nanocomposite‐modified glassy carbon electrode

A polyaniline (PANI)‐Cu nanocomposite‐modified electrode was fabricated by the electrochemical polymerization of aniline and the electrodeposition of copper under constant potentials on a glassy carbon electrode (GCE), respectively. Scanning electron microscope result shows that the PANI‐Cu composite on the surface of the GCE displays the nanofibers having an average diameter of about 80 nm with lengths varying from 1.1 to 1.2 μm. The electrode exhibits enhanced electrocatalytic behavior to the reduction of nitrite compared to the PANI‐modified GCE. The effects of applied potential, pH value of the detection solution, electropolymerization charge, temperature, and nitrite concentration on the current response of the composite‐modified GCE were investigated and discussed. Under optimal conditions, the PANI‐Cu composite‐modified GCE can be used to determine nitrite concentration in a wide linear range (n = 18) of 0.049 and 70.0 μM and a limit of detection of 0.025 μM. The sensitivity of the electrode was 0.312 μA μM^?1 cm^?2. The PANI‐Cu composite‐modified GCE had the good storage stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A highly selective electrochemical sensor for l‐tryptophan based on a screen‐printed carbon electrode modified with poly‐p‐phenylenediamine and CdS quantum dots

A new highly selective electrochemical sensor for the determination of l ‐tryptophan was proposed by modifying the surface of screen‐printed carbon electrodes (SPCEs). The surface of SPCE was firstly modified by electropolymerization of p‐phenylenediamine (PPD). The polymer film was then covalently linked with cysteamine capped cadmium sulfide quantum dots (Cys‐CdS QDs) by using glutaraldehyde (GA) as a cross‐linker resulted in an organic–inorganic hybrid composite film (QDs/GA/PPD/SPCE). The modified electrode was applied as a working electrode for detecting various amino acids. It was found that the modified electrode gave an electrochemical response selectively to l ‐tryptophan over other amino acids. The experimental parameters, including pH of solution, buffer types, electropolymerization cycles, scan rate, and accumulation time, were studied and optimized. The proposed sensor can be used to detect l ‐tryptophan with a low detection limit of 14.74 µmol L^?1 with good precision and the relative standard deviation less than 3.7%. The modified electrode was used to detect l ‐tryptophan in beverage samples and gave satisfactory recoveries from 91.9 to 104.9%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40356.     

Facile synthesis of graphene/polypyrrole 3D composite for a high‐sensitivity non‐enzymatic dopamine detection

One kind of nanocomposite consisting of graphene and polypyrrole was synthesized via a facile and mild way with the assistant of microwave irradiation. The synthesis route was embedding the polypyrrole into the graphene flakes to form a 3D structure, to achieve larger active surface and higher electro‐catalysis property. Structures and components of the composite were measured by X‐ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. A stronger electrochemical response of electrode with modified resultant was observed in the electrochemical test. Dopamine sensor based on the composite showed a sensitivity of 363 μA mM ^?1 cm^?2, a linear range of 1 × 10^?4 M to 1 × 10^?3 M , and a detection limit of 2.3 × 10^?6 M (S/N = 3). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44840.     

Preparation of block copolymers via metal‐free visible‐light‐induced ATRP for the detection of lead ions

Polyacrylamide‐b‐poly(methacrylic acid) was prepared on the surface of Au electrode (Au/PAM/PMAA) for Pb²⁺ ion electrochemical sensing via metal‐free visible‐light‐induced atom transfer radical polymerization, which was very simple, convenient, and environmentally friendly. Au/PAM/PMAA was carefully examined by cyclic voltammetry, electrochemical impedance spectroscopy, and X‐ray photoelectron spectroscopy. Further, Au/PAM/PMAA was successfully used for the determination of Pb²⁺ ion by differential pulse anodic stripping voltammetry. Under the optimal conditions, a linear response from 1.0 × 10^?11 to 1.0 × 10^?4 mol/L with detection limit of 2.5 × 10^?12 mol/L (S/N = 3) was achieved from the results of experiments. Comparing with similar Pb²⁺ sensors, the broader linear range and lower detection limit suggested the promising prospect of Au/PAM/PMAA. In a word, the work of this article had an important significance for the polymer‐modified electrodes and the sensitive detection of Pb²⁺. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45863.     

Electrochemical behaviour of glassy carbon electrodes modified with aryl groups

The electrochemical modification of the glassy carbon (GC) electrode surface with biphenyl, 1-naphthyl, 2-naphthyl, 4-bromophenyl, 4-decylphenyl and 4-nitrophenyl groups was performed by the diazonium reduction method. The blocking behaviour of aryl films grafted by three different procedures was compared. Oxygen reduction was studied on these modified GC electrodes using the rotating disk electrode (RDE) method. The highest blocking efficiency for O₂ reduction was observed for 4-bromophenyl groups. The barrier properties of aryl-modified GC surfaces were also characterised using Fe(CN)₆³⁻ and dopamine redox probes. Electrochemical measurements were carried out in 0.1 M K₂SO₄ containing 1 mM K₃Fe(CN)₆ and in 0.1 M H₂SO₄ containing 1 mM dopamine using cyclic voltammetry (CV). The blocking action varied significantly depending on the surface modifier used and the solution based redox species studied.     

Effect of heat‐treatment on the performance of gas barrier layers applied by atomic layer deposition onto polymer‐coated paperboard

The effect of heat treatment on the gas barrier of the polymer‐coated board further coated with an Al₂O₃ layer by atomic layer deposition (ALD) was studied. Heat treatment below the melting point of the polymer followed by quenching at room temperature was used for the polylactide‐coated board [B(PLA)], while over‐the‐melting‐point treatment was utilized for the low‐density polyethylene‐coated board [B(PE)] followed by quenching at room temperature or in liquid nitrogen. Heat treatment of B(PLA) and B(PE) followed by quenching at room temperature improved the water vapor barrier. However, because of the changes in the polymer morphology, quenching of B(PE) with liquid nitrogen impaired the same barrier. No improvement in oxygen barrier was observed explained by, e.g., the spherulitic structure of PLA and the discontinuities and possible short‐chain amorphous material around the spherulites forming passages for oxygen molecules. This work emphasizes the importance of a homogeneous surface prior to the ALD growth Al₂O₃ barrier layer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Study of nimesulide and its determination using multiwalled carbon nanotubes modified glassy carbon electrodes

A new method for the determination of nimesulide was established based on the multiwalled carbon nanotubes (MWCNTs) modified glassy carbon electrode (MWCNTs/GCE). In 0.2 M PBS (pH 6.6) buffer solution, the MWCNTs/GCE showed a remarkable catalytic and enhancement effect on reduction of the nimesulide. The reduction peak potential of nimesulide shifted positively from −0.665 V at bare GCE to −0.553 V at MWCNTs/GCE, and the sensitivity increased ca. 7 times. A linear dynamic range of 3.2 × 10⁻⁷-6.5 × 10⁻⁵ M (R = 0.9992) with a detection limit of 1.6 × 10⁻⁷ M was obtained. The electrochemical behaviors of nimesulide were studied and electron-transfer coefficient (α = 0.45), proton number (X = 1) and electron-transfer number (n = 2) have been determined. This method has been used to determine the content of nimesulide in medical tablets. The recovery was determined to be 93.2-106.2% by means of standard addition method. Compared with UV-vis spectrometry, the method was not remarkable difference.     

Activation of glassy carbon electrodes by photocatalytic pretreatment

This paper describes a simple and rapid photocatalytic pretreatment procedure that removes contaminants from glassy carbon (GC) surfaces. The effectiveness of TiO₂ mediated photocatalytic pretreatment procedure was compared to commonly used alumina polishing procedure. Cyclic voltammetric and chronocoulometric measurements were carried out to assess the changes in electrode reactivity by using four redox systems. Electrochemical measurements obtained on photocatalytically treated GC electrodes showed a more active surface relative to polished GC. In cyclic voltammograms of epinephrine, Fe(CN)₆^3−/4− and ferrocene redox systems, higher oxidation and reduction currents were observed. The heterogeneous electron transfer rate constants (k^o) were calculated for Fe(CN)₆^3−/4− and ferrocene which were greater for photocatalytic pretreatment. Chronocoulometry was performed in order to find the amount of adsorbed methylene blue onto the electrode and was calculated as 0.34 pmol cm⁻² for photocatalytically pretreated GC. The proposed photocatalytic GC electrode cleansing and activating pretreatment procedure was more effective than classical alumina polishing.     

Improved specific capacity of sulfur/starch‐based activated carbon spheres composites by polyaniline‐based carbon encapsulation strategy

Lithium‐sulfur battery is one of the most promising electrochemical energy storage systems because of its high theoretical specific capacity and energy density. When carbon materials are used for immobilizing sulfur, the technical challenge is designing their framework to relieve the shuttle effect of polysulfides intermediates and the volume change of sulfur, and to improve the conductivity of sulfur. Herein, polyaniline‐based carbon (PANI‐C) coated corn starch‐based activated carbon spheres (ACS@PANI‐C) was prepared and used as hosts of sulfur, which can effectively combine the advantages of physical entrapment and chemical binding interactions of sulfur species. The results of electrochemical performance test indicate that S/ACS@PANI‐C composites exhibit much better electrochemical performance than S/ACS composites. Its reversible capacities at 320, 480, 800 and 1600 mA g^?1 are 687, 582, 504 and 393 mAh g^?1, respectively. The improved electrochemical performance can be attributed to the PANI‐C which can also act as a flexible cushion to accommodate volume changes of sulfur cathode as well as a barrier to trap soluble polysulfide intermediates during the charge–discharge process. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46544.     

Electrooxidation of DNA at glassy carbon electrodes modified with multiwall carbon nanotubes dispersed in polyethylenimine

This work reports the electrochemical response of the complex between dsDNA and PEI formed in solution and at the surface of glassy carbon electrodes (GCE) modified with a dispersion of multi-walled carbon nanotubes in polyethylenimine (CNT-PEI). Scanning Electron Microscopy and Scanning Electrochemical Microscopy demonstrate that the dispersion covers the whole surface of the electrode although there are areas with higher density of CNT and, consequently, with higher electrochemical reactivity. The adsorption of DNA at GCE/CNT-PEI is fast and it is mainly driven by electrostatic forces. A clear oxidation signal is obtained either for dsDNA or a heterooligonucleotide of 21 bases (oligoY) at potentials smaller than those for the oxidation at bare GCE. The comparison of the behavior of DNA before and after thermal treatment demonstrated that the electrochemical response highly depends on the 3D structure of the nucleic acid.     

Electrochemical behavior of glassy carbon electrodes modified by multi-walled carbon nanotube/surfactant films in a buffer solution and an ionic liquid

The electrochemical behavior of glassy carbon (GC) electrodes coated with multi-walled carbon nanotube (MWCNT)/surfactant films was studied in an ionic liquid and a phosphate buffer solution (pH = 6.86), using cyclic voltammetry. The dispersion of MWCNTs in different media was investigated by scanning and transmission electron microscopy. Cast films of MWCNT/zwitterionic dodecyldimethylamine oxide on a GC electrode show a typical redox couple in phosphate buffer solution, which is better than that of MWCNT/anionic sodium dodecyl sulfate and cationic alkyltrimethylammonium bromide. However in the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), the GC electrode modified by MWCNT/cationic surfactant films shows a well-defined irreversible reduction of MWCNTs. The cyclic voltammograms clearly show that the surfactant hydrophilic group plays an important role in the electrochemical behavior of the MWCNTs. The electrolytes also have an important effect. In an ionic liquid, the strong binding of the ionic liquid cations with the MWCNTs may change the structure of the modified films and lead to changes of electrochemical behavior.     

Electroreduction of oxygen on glassy carbon electrodes modified with in situ generated anthraquinone diazonium cations

The electrochemical reduction of oxygen on glassy carbon (GC) electrodes modified with in situ generated diazonium cations of anthraquinone (AQ) has been studied using the rotating disk electrode (RDE) technique. The electrografting of the GC electrodes was carried out in two different media: in acetonitrile and in an aqueous acidic solution (0.5 M HCl). 1- and 2-Aminoanthraquinone were used as starting compounds for the formation of the corresponding diazonium derivatives. The anthraquinone diazonium cations were generated by reaction of the aminoanthraquinones with tert-butyl nitrite and sodium nitrite in acetonitrile and in 0.5 M HCl, respectively. For comparison purposes, the previously synthesised and crystallised diazonium tetrafluoroborates of anthraquinone were used for the GC surface modification. Cyclic voltammetry was employed to determine the surface concentration of AQ in O₂ free 0.1 M KOH. The electrocatalytic behaviour towards O₂ reduction was similar for all the AQ-modified electrodes studied. The kinetic parameters of oxygen reduction were determined using a surface redox catalytic cycle model. The rate constant of the reaction between the semiquinone radical anion of AQ and molecular oxygen was virtually independent of the point of attachment of the quinone to the electrode surface.     

The viscoelastic properties of polymer‐modified asphalts

The linear viscoelastic properties of one family of base asphalts, unmodified or modified by the simple addition of an elastomer or by further in‐situ crosslinking, have been investigated. The time‐temperature superposition principle was shown to be valid for the base as well as for the modified asphalts. The addition of the elastomer styrene‐butadiene (SB) copolymer increased drastically the storage modulus and the elastic character of the asphalts. The thermal susceptibility of the polymer modified asphalts was considerably reduced and this combined with an increased resistance to deformation (larger complex modulus) suggests much better performances for road applications. The chemically modified asphalt containing 3% SB showed similar viscoelastic properties as the physical blend containing 6% SB.     

Molecularly imprinted electrochemical sensor for the determination of ampicillin based on a gold nanoparticle and multiwalled carbon nanotube‐coated pt electrode

A novel molecularly imprinted electrochemical sensor was developed for the sensitive and selective determination of ampicillin (AMP). The sensor was prepared on a platinum electrode modified with multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs), and a thin film of molecularly imprinted polymers (MIPs). MWCNTs and AuNPs were introduced to enhance the sensor's electronic transmission and sensitivity. The molecularly imprinted polymer (MIP) was synthesized using AMP as the template molecule, methacrylic acid as functional monomer, and ethylene glycol maleic rosinate acrylate (EGMRA) as cross‐linker. The performance of the proposed imprinted sensor was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results showed that the imprinted film displayed a fast and sensitive response to AMP. Under optimal conditions, response peak current had a linear relationship with the concentration of AMP in the range of 1.0 × 10^?8 mol/L to 5.0 × 10^?6 mol/L and a detection limit of 1.0 × 10^?9 mol/L (S/N = 3). This imprinted sensor was used to detect AMP in food samples with recoveries of 91.4–105%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40613.     

改性活性炭吸附除砷的研究

以小麦秸秆、木屑、煤渣等所制备的活性炭及其活性炭负载铁作为吸附剂,用于水中As（Ⅲ）的去除。考察了活性炭种类、吸附时间、吸附温度、溶液pH值和吸附剂投加量等对As（Ⅲ）去除的影响。结果表明,木屑制备的活性炭所负载铁作为吸附剂,对水中As（Ⅲ）的去除效果最好;As（Ⅲ）的去除率随吸附时间、吸附温度、溶液pH值和吸附剂投加量的增加而增加。     

Aniline‐nonamer segmented polyurea: A facile electrocatalyst for detection of ascorbic acid

An unprecedented A‐B‐A type block copolymer electroactive polyurea (EPU) is designed and synthesized with tetraaniline dimer and 1,4‐phenylenediamine via an oxidative coupling, where aniline–nonamer and hexamethylene di‐urea constitute two segments. The EPU was characterized by spectral techniques such as Fourier transform infrared spectroscopy, nuclear magnetic resonance, and UV–vis spectra. The structural characterization of the prepared EPU was obtained by powder X‐ray diffraction and X‐ray photoelectron spectroscopy techniques. EPU reorganizes into core–shell microcapsules in presence of aqueous acetic acid/n‐octane interface. These microcapsules exhibited a wide range of pH responses in their absorption spectrum (UV–vis). The EPU is modified as carbon paste electrode which exhibits a remarkable electrocatalytic oxidation of ascorbic acid (AA, Vitamin C) in 0.2 M and pH 7.0 phosphate buffer solution. The carbon paste electrode is useful in sensing as low as 50 µM of ascorbic acid. This can open up new opportunities for fast, simple detection of AA providing a promising platform for sensor/biosensor designs for AA detection. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46630.     

Electro-oxidation of chlorophenols at glassy carbon electrodes modified with polyNi(II)complexes

The effect of the ligand macrocycle (phenylporphyrin (PP) or phthalocyanine (Pc)) and of the ligand substituent (NH₂ or SO₃⁻) on the catalytic activity for the electro-oxidation in a pH 11 buffer electrolyte of 2- and 4-chlorophenol (2-CP and 4-CP), 2,4- and 2,6-dichlorophenol (2,4-DCP and 2,6-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) at glassy carbon electrodes modified with electropolymerized Ni(II) macrocycles was studied. The polyphenolic residue deposited at the electrode surface was characterized by cyclic voltammetry, impedance measurements, ex situ Fourier transform infrared spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). A band of aliphatic CO stretching in the IR spectrum of the fouling film produced by potential cycling in 2,4,6-TCP indicated that the aromatic ring had been broken, yielding ketones, aldehydes and/or carboxylic acids. The sulphonated Ni(II) polymers, which showed the Ni(III)/Ni(II) process in the CV, had XP spectra typical of paramagnetic Ni(II), indicating that they contained Ni(OH)₂ clusters. On the contrary, the CVs of the amino Ni(II) did not show the Ni(III)/Ni(II) process at all, this process appearing only after previous activation by potential cycling, and only to a small extent. As was to be expected, the XP spectra of activated amino films corresponded to diamagnetic Ni(II), showing that the concentration of Ni(OH)₂ clusters was very small. The amino films were less active than the sulpho films for the oxidation of chlorophenols, in agreement with the lower concentration of Ni(OH)₂ clusters in the former films. For all electrodes the highest activity was observed for 2,4,6-TCP, since its oxidation yields a phenolic residue which is much more porous than those produced by the other CPs.     

Poly(taurine)/MWNT-modified glassy carbon electrodes for the detection of acetaminophen

A novel dye-polymer/CNT, poly(taurine)/MWNT-modified glassy carbon electrode was fabricated. This electrode is based on an electrochemically polymerized taurine layer coated on a MWNT film. The application of this electrode for voltammetric detection of acetaminophen is described. The electroactive surface area of the modified electrode was calculated to be 0.37 cm². Acetaminophen is oxidized at 0.38 V and then reduced at 0.27 V on the modified electrode. The irreversible oxidation process is due to the conversion of acetaminophen into imidogenquinone; the reduction process is ascribed to the reverse electrode reaction. The adsorption-controlled anodic peak current is proportional to the acetaminophen concentration (from 1.0 μM to 0.1 mM) with a detection limit of 0.5 μM. The detection of acetaminophen in drugs was conducted.     

Amperometric detection of hydrogen peroxide at nano-nickel oxide/thionine and celestine blue nanocomposite-modified glassy carbon electrodes

A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with nickel oxide (NiOx) nanoparticles and water-soluble dyes. By immersing the GC/NiOx modified electrode into thionine (TH) or celestine blue (CB) solutions for a short period of time (5–120 s), a thin film of the proposed molecules was immobilized onto the electrode surface. The modified electrodes showed stable and a well-defined redox couples at a wide pH range (2–12), with surface confined characteristics. In comparison to usual methods for the immobilization of dye molecules, such as electropolymerization or adsorption on the surface of preanodized electrodes, the electrochemical reversibility and stability of these modified electrodes have been improved. The surface coverage and heterogeneous electron transfer rate constants (k_s) of thionin and celestin blue immobilized on a NiOx-GC electrode were approximately 3.5 × 10⁻¹⁰ mol cm⁻², 6.12 s⁻¹, 5.9 × 10⁻¹⁰ mol cm⁻² and 6.58 s⁻¹, respectively. The results clearly show the high loading ability of the NiOx nanoparticles and great facilitation of the electron transfer between the immobilized TH, CB and NiOx nanoparticles. The modified electrodes show excellent electrocatalytic activity toward hydrogen peroxide reduction at a reduced overpotential. The catalytic rate constants for hydrogen peroxide reduction at GC/NiOx/CB and GC/NiOx/TH were 7.96 (±0.2) × 10³ M⁻¹ s⁻¹ and 5.5 (±0.2) × 10³ M⁻¹ s⁻¹, respectively. The detection limit, sensitivity and linear concentration range for hydrogen peroxide detection were 1.67 μM, 4.14 nA μM⁻¹ nA μM⁻¹ and 5 μM to 20 mM, and 0.36 μM, 7.62 nA μM⁻¹, and 1 μM to 10 mM for the GC/NiOx/TH and GC/NiOx/CB modified electrodes, respectively. Compared to other modified electrodes, these modified electrodes have many advantages, such as remarkable catalytic activity, good reproducibility, simple preparation procedures and long-term stabilities of signal responses during hydrogen peroxide reduction.     

Electrochemical sensors for hemoglobin and myoglobin detection based on methylene blue-multiwalled carbon nanotubes nanohybrid-modified glassy carbon electrode

An effective electrochemical sensors for hemoglobin (Hb) and myoglobin (Mb) detection was firstly developed using a simple procedure of self-assembled methylene blue-multiwalled carbon nanotubes (MB-MWNTs) nanohybrid modified on glassy carbon electrode without using any enzymes immobilization. The direct electrochemical and electrocatalytic behaviors of the modified electrode were studied using cyclic voltammetry (CV) and flow injection analysis (FIA) with amperometry. The performance of the sensor was investigated and optimized and the system was evaluated by monitoring Hb and Mb concentrations. The developed MB-MWNTs nanohybrid modified electrode showed excellent electrocatalytic activity for reduction of Hb and Mb with good stability, sensitivity and reproducibility (RSD = 3.05% and 4.5% for 50 successive injections of Hb and Mb, respectively). Under optimal conditions, the catalytic currents are linearly proportional to the concentrations of Hb and Mb in the wide range from 5 nM to 2 μM and 0.1 to 3 μM, and the corresponding detection limits are 1.5 nM and 20 nM (S/N = 3), respectively. This approach provides improved detection limit over other previous works and may provide a novel and efficient platform for the fabrication of sensors for other heme proteins.