Novel Electrochemical Sensor Based on Molecularly Imprinted Polymers with MWCNTs-SiO2 for Selective and Sensitive Detecting 2,4-D

In this study, we introduced molecular imprinting combined with electrochemical method to determine trace 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide in standard solution and actual samples. For this purpose, we synthesis of vinyl silica coated MWCNTs in alkaline environment with surfactant, molecularly imprinted polymers were prepared on the surface of MWCNTs by free radical polymerization, following the composite materials were dissolved in chitosan solution and dropped on the glassy carbon electrode. The functionalized materials were characterized by fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetry and nitrogen adsorption desorption. Electrochemical performance of molecularly imprinted membrane was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry. Selectivity, stability and reproducibility of the sensors were also studied and discussed. A good linear relationship for supervising 2,4-D from 1.0?×?10^?4 to 1.0?×?10^?8 mol L^?1 with the correlation coefficient of 0.994 and a low LOD of 4.270?nmol?L^?1 (S/N?=?3). The electrochemical sensor has been successfully applied to detect 2,4-D with a recovery rate ranges from 96.2 to 102.4% and a relative standard deviation of less than 4.74%. This work provides potential ideas for detection of trace 2,4-D in real samples.

     

A Novel Amperometric Sensor for Salicylic Acid Based on Molecularly Imprinted Polymer-Modified Electrodes

A novel electrochemical MIP-sensor for salicylic acid (SA) has been synthesized firstly by electropolymerizing o-phenylenediamine on glassy carbon electrode in presence of template molecule (salicylic acid). The response of the sensor to SA is investigated by square wave voltammetry (SWV). The linearity is obtained over a concentration range of 6 × 10^?5 ～ 1 × 10^?4 mol/L (R² = 0.9961). And the detection limit of SA is about 2 × 10^?5 mol/L. The sensor exhibits good selectivity for salicylic acid by virtue of the interaction between molecularly imprinted binding sites and the template.     

Determination of epigallocatechin‐3‐gallate with a high‐efficiency electrochemical sensor based on a molecularly imprinted poly(o‐phenylenediamine) film

An electrochemical molecularly imprinted polymer (MIP) sensor for detecting the existence of epigallocatechin‐3‐gallate (EGCG) in tea and its products was successfully developed on the basis of a glassy carbon electrode modified with an electropolymerized nonconducting poly(o‐phenylenediamine) film. The properties of the electrode were characterized by cyclic voltammetry, differential pulse voltammetry, and infrared spectroscopy. The template molecules could be rapidly and thoroughly removed by methanol/acetic acid. The linear response range for EGCG was 5.0 × 10^?7–1.0 × 10^?4 mol/L, and the limit of detection was as low as 1.6 × 10^?7 mol/L. The prepared MIP sensor could discriminate between EGCG and its analogs. In addition, satisfactory results were obtained in the detection of real tea samples. The results of our investigation indicate that the MIP sensor was useful for the determination of EGCG with excellent selectivity, high sensitivity, repeatability, and reproducibility. This MIP sensor provides the potential for monitoring the variation of EGCG content during the industrial processes and for predicting the quality of tea and its products. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Voltammetric determination of alkannin using an Au nanoparticles–poly(diallyldimethylammonium chloride)-functionalized graphene nanocomposite film

An electrochemical sensor based on Au nanoparticles (AuNPs)–poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (AuNPs–PDDA-G) nanocomposite was fabricated for the sensitive detection of alkannin. The nanocomposite was characterized by X-ray diffraction, ultraviolet/visible spectra, scanning electron microscopy, and transmission electron microscopy. Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical behaviors of alkannin on the AuNPs–PDDA-G nanocomposite film-modified glassy carbon electrode. This electrochemical sensor displayed satisfactory analytical performance for alkannin detection over a range from 5.0 nmol L^?1 to 3.0 μmol L^?1 with a detection limit of 1.4 nmol L^?1 (S/N = 3). Moreover, the sensor also exhibited good reproducibility and stability, and could be used for the detection of alkannin in real samples with satisfactory results.     

Gold nanoparticle ensemble on polydopamine/graphene nanohybrid as a novel electrocatalyst for determination of baicalein

A facile and green approach is used to synthesize polydopamine (PDA) functionalized reduced graphene oxide (RGO) via the self‐polymerization of dopamine (DA) under alkaline conditions. The obtained reduced RGO/PDA composite facilitate Au precursor adsorption. Then Au nanoparticles are reduced and assemble onto the surface of RGO/PDA composite form reduced RGO/PDA/gold (RGO/PDA/Au) nanocatalysts. After that, a sensitive electrochemical sensor for baicalein is fabricated based on RGO/PDA/Au nanocatalysts. In this method, the hydroxyl units of PDA can form hydrogen bonding with the phenolic hydroxyl groups of baicalein, making baicalein easily adsorb on the modified electrode surface to enhance the electrochemical response. The electrochemical mechanism of baicalein on the RGO/PDA/Au nanocatalysts modified GCE is thoroughly investigated by cyclic voltammetry. The fabricated electrochemical sensor show good electrochemical activity for baicalein. The linear range of baicalein is 1 × 10^?8 to 15 × 10^?6 mol L^?1 with the detection limit of 3.1 × 10^?9 mol L^?1. Furthermore, the proposed electrochemical sensor can be used to detect real sample. The results reveal that this method provides a new avenue for electrochemical investigation of baicalein in biochemical, pharmaceutical, and clinical research. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 46720.     

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.     

基于对巯基苯胺膜的高灵敏己烯雌酚印迹传感器的制备及应用

通过自组装技术，分别以金硫键（Au—S）和氢键在羧基化多壁碳纳米管（CMWCNTs）和纳米金（AuNPs）修饰的电极表面成功组装功能单体对巯基苯胺（p-ATP）和模板分子己烯雌酚（DES），在含有p-ATP、DES、氯金酸和电聚合介质四丁基高氯酸铵的聚合液中采用电聚合的方法在组装电极表面形成聚合物膜，并用50%乙醇-0.1mol/L硫酸水溶液（1∶1，体积比）洗脱模板分子，成功制备了用于检测己烯雌酚的分子印迹电化学传感器。采用循环伏安法和差分脉冲伏安法研究印迹传感器的印迹效果和分析性能，并将该传感器应用于食品中己烯雌酚的快速检测。在最佳条件下，己烯雌酚的线性范围为1.0×10^-9～1.0×10^-5mol/L，检出限为3.3×10^-10mol/L，样品加标平均回收率为83.46%～98.21%，相对标准偏差（RSD）在1.01%～3.74%之间（n=5）。该传感器操作简单、检测快速灵敏、成本低、抗干扰能力强、稳定性好，有重要的应用价值。     

分子印迹电化学传感器检测链霉素

为实现链霉素的快速、灵敏测定,将特异性强的分子印迹技术与检测灵敏度高的电化学检测方法结合,构建链霉素分子印迹电化学传感器。以链霉素为模板分子,吡咯为功能单体,利用电化学聚合方法制备分子印迹聚合物(MIP)膜。在最优化实验条件下,以铁氰化钾为探针,利用循环伏安法(CV)对链霉素进行定量测定及传感器性能研究。结果表明:传感器线性范围为5.00×10~(-8)～8.00×10~(-5)mol/L,最低检出限(LOD)为3.45×10~(-8)mol/L,为链霉素的测定提供了高效的方法。     

Zinc ion-imprinted polymer based on silica particles modified carbon paste electrodes for highly selective electrochemical determination of zinc ions

ABSTRACT

In this study, Zn(II) ion-imprinted polymer was prepared on the surface of vinyl silica particles and applied for detection of Zn(II) ions using differential pulse voltametry. The ion- imprinted polymer particles were prepared by free radical polymerization. The prepared particles were characterized by different morphological and elemental techniques. The ion-imprinted particles were used to fabricate the carbon paste electrode as a zinc ions sensor. The modified zinc sensor showed linear response in the concentration range 6.12 × 10^?9 to 4.59 × 10^?8 mol L^?1. The limit of detection and limit of quantification of the electrode were 1.351 × 10^?8 and 4.094 × 10^?8 mol L^?1, respectively.     

Alternative molecularly imprinted membranes from a derivative of natural polymer,cellulose acetate

Molecularly imprinted polymeric membranes were prepared from cellulose acetate (CA), of which acetyl content was 40%, by applying the alternative molecular imprinting technique. The Z‐d ‐Glu imprinted polymeric membranes thus obtained recognized d ‐Glu in preference to l ‐Glu from racemic Glu mixtures and vice versa. The affinity constants between Glu and the chiral recognition site for two kinds of membranes were determined to be 3.1 × 10³ mol⁻¹ dm³ from the adsorption isotherm of d ‐Glu or L ‐Glu in the molecularly imprinted CA membranes. Enantioselective electrodialysis was attained with the present membranes reflecting their adsorption selectivity. d ‐Glu was preferentially permeated through the Z‐d ‐Glu imprinted CA membrane, whereas L ‐Glu was permeated through the Z‐L ‐Glu imprinted CA membrane. The present study suggests that the molecularly imprinted CA membranes are applicable to the optical resolution of racemic amino acids. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 493–499, 1999     

Preparation of poly(9‐aminoacridine)‐modified electrode and its application in the determination of dopamine and ascorbic acid simultaneously

A novel modified electrode was fabricated with 9‐aminoacridine by electropolymerization in the phosphate buffer solution (PBS) (pH 7.4) and was characterized by cyclic voltammetry (CV). The modified electrode showed excellent electrocatalytic effect and high stability toward the electrochemical oxidation of dopamine (DA) and ascorbic acid (AA). Also, it showed a high stability for the determination of DA and AA simultaneously. Well‐separated voltammetric peaks were observed for DA and AA on the modified electrode. The separation of two anodic peaks was 170 mV, which was large enough to eliminate the interference of AA and determine DA. The differential pulse voltammograms (DPV) were used for the measurement of DA by means of the poly(9‐aminoacridine)‐modified electrode in PBS at pH 7.4. A linear response toDA was observed in the concentration range from 1.5 × 10^?6 to 3.5 × 10^?3 mol L^?1 with a correlation coefficient of 0.9998 and a detection limit (S/N = 3) of 1.0 × 10^?7mol L^?1. The proposed method was used to determine DA in DA‐hydrochloride injection and showed excellent sensitivity and recovery. The ease of fabrication, good reproducibility, high stability, and low cost of the modified electrode are the promising features of the proposed sensor. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3864–3870, 2007     

Electrochemical copper (II) sensor based on chitosan covered gold nanoparticles

This study outlines a new sensing platform based on glassy carbon electrodes modified by gold nanoparticles (AuNPs) for the determination of heavy metal. A glassy carbon electrode was modified by chitosan stabilized AuNPs. AuNPs were prepared by reducing gold salt with a polysaccharide chitosan. Here, chitosan acted as a reducing/stabilizing agent. The AuNPs were characterized with UV–Visible absorption spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Chitosan covered AuNPs were immobilized on the glassy carbon electrode for the determination of Cu (II) in aqueous solutions. The electrochemical determination of Cu (II) ions was performed using the differential pulse voltammetry technique. Some parameters for Cu (II) determination, such as pH, preconcentration time and electrolysis potential of Cu (II), were optimized. The detection limit was calculated as 5 × 10^?9 mol L^?1 by means of the 3:1 current-to-noise ratio. The interference of Cr(III), Fe(II), Ni(II), Pb(II), Mg(II), Zn(II), Ba(II) ions was investigated and showed a negligible effect on the electrode response. Recovery studies were carried out using tap water.     

A sensitive voltammetric sensor based on synergistic effect of graphene–polyaniline hybrid film for quantification of calcium antagonist lercanidipine

A chemically modified sensor based on the synergistic effect of graphene and polyaniline for electrochemical sensing of calcium antagonist lercanidipine (LCP) has been developed. Scanning electron microscopy, electrochemical impedance spectroscopy, square‐wave voltammetry, and cyclic voltammetry were utilized to characterize the morphology and electroanalytical performance of the fabricated sensor. Under optimized conditions, reduction peak current was linear over the wide concentration range from 5 to 125 ng mL^?1 with correlation coefficient of 0.9998. The limit of detection and the limit of quantification were found to be 1.94 and 5.89 ng mL^?1. The developed sensor also exhibited good reproducibility and long‐term stability. In addition, the proposed method was successfully applied to the determination of LCP in pharmaceutical formulation which is proved by recovery studies. Graphene–polyaniline composites are expected to be promising material for biosensing applications because of the ease of fabrication, excellent electrochemical performance, and high electroactive surface area. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40959.     

Application of a C6‐OH of chitosan immobilized cyclodextrin derivates on an electrochemical H2O2 biosensor

Biosensor detecting techniques have attracted much attention in the content determination of H₂O₂, which has been used illegally as a food additive. An electrochemical biosensing membrane for the detection of H₂O₂ was developed with C6‐OH of chitosan immobilized cyclodextrin derivates (6‐CD–CTS), which possessed a high cyclodextrin loading capacity (2.12 × 10^?4 mol/g), as the carrier. The biosensor was prepared through the inclusion of ferrocene as the electron mediator in a hydrophobic cavity of cyclodextrin and crosslinking catalase (CAT) to 2‐NH₂ of 6‐CD–CTS. The ferrocene‐included complex was evaluated by ultraviolet–visible spectrophotometry and thermogravimetric analysis. Its electrochemical behavior was also studied. The impact of the reaction conditions on the CAT immobilization capacity was evaluated. When previous membrane was used to detect the concentration of H₂O₂ (C_H2O2), we found that the catalysis of CAT and the signal amplification of ferrocene had a major impact on the cyclic voltammograms. The optimal working pH of the modified electrode was 7.0. The peak current (I) had a linear relationship with the H₂O₂ concentration (CH₂O₂) in the range 1.0 × 10^?4 to 1.0 × 10^?3 mol/L. The linear regression equation was I = 0.00475C_H2O2 ? 0.03025. The detection limit was 10^?6 mol/L. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41499.     

A chemiluminescence sensor for determination of epinephrine using graphene oxide–magnetite-molecularly imprinted polymers

A chemiluminescence (CL) sensor for the determination of epinephrine using the system of luminol–NaOH–H₂O₂ based on a graphene oxide–magnetite-molecularly imprinted polymer (GM-MIP) is described. The epinephrine GM-MIP was synthesized using graphene oxide (G) which improved the adsorption capacity, and magnetite nanoparticles which made the polymers easier to use in the sensor. The adsorption performance and properties were characterized. The GM-MIP was used in CL analysis to increase the selectivity and the possible mechanism was also discussed. The CL sensor responded linearly to the concentration of epinephrine over the range 1.04 × 10^?7–7.06 × 10^?3 mol/L with a detection limit of 1.09 × 10^?9 mol/L (3σ). The relative standard deviation for determination was 3.87%. On the basis of speediness and sensitivity, the sensor is reusable and shows a great improvement in selectivity and adsorption capacity over other sensors. The sensor had been used for the determination of epinephrine in drug samples.     

Molybdate‐doped copolymer coatings for corrosion prevention of stainless steel

The polypyrrole and polyaniline copolymer coating (PPy‐PAni) and PPy‐PAni doped with sodium molybdate copolymer coating ( ) were synthesized on stainless steel by cyclic voltammetry. The effect of molybdate on the passivation of stainless steel was investigated by linear sweep voltammetry in 0.2 mol L^?1 of oxalic acid. The corrosion prevention performances of these copolymer coatings for stainless steel were investigated by linear sweep voltammetry, electrochemical impedance spectroscopy in 1 mol L^?1 of sulfuric acid, and potentiodynamic polarization in 0.1 mol L^?1 of hydrochloric acid. Copolymer coating doped with molybdate could accelerate the formation of the passive oxide film and have better corrosion prevention efficiencies than PPy‐PAni coating on stainless steel. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40602.     

Electrochemical characteristics and catalytic activity of polyaniline doped with ferrocene perchlorate

A new‐doped method based on electrochemical polymerization of aniline in the presence of ferrocene perchlorate and perchloric acid was presented. Polyanilines (PAn and PAnFc) were polymerized in the solution of perchloric acid and the solution containing ferrocene perchlorate and perchloric acid, respectively. Both flame atomic absorption spectrometry and infrared spectrum indicated that ferrocene perchlorate was assured to be doped into the polyaniline. We presumed that ferrocene perchlorate was combined via electrostatic adsorption onto the chain of polyaniline. The effect of pH on the electrochemical characteristics of PAn and PAnFc was studied by cycle voltammetry. Compared with PAn prepared in the absence of ferrocene perchlorate, PAnFc prepared in the presence of ferrocene perchlorate has a rather high electrochemical activity at pH > 4. The electrochemical oxidation of ascorbic acid (AA) on both PAn film and PAnFc film modified Pt electrode was also performed. The results indicated that the catalytic activity of the PAnFc film to AA was better than that of the PAn film. The anodic peak currents of AA (measured by constant potential amperometry) increased linearly with the concentration of AA in the range of 8.0 × 10^?5–1.0 × 10^?2 mol/L. The detection limit (S/N = 3) obtained was 1.0 × 10^?5 mol/L. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5633–5639, 2006     

Polypyrrole–multiwalled carbon nanotubes composites as immobilizing matrices of ascorbate oxidase for the facile fabrication of an amperometric vitamin C biosensor

An amperometric vitamin C biosensor was facilely fabricated by the immobilization of ascorbate oxidase (AO) on polypyrrole (PPy)–multiwalled carbon nanotubes (MWCNTs) composites with a one‐step electrodeposition technique in a 0.05M phosphate buffer solution (pH 6.5). The cyclic voltammetry, IR spectral analysis, electrochemical impedance spectroscopy, and scanning electron microscopy measurements indicated that AO was successfully immobilized on the PPy–MWCNT composites. The optimization of the biosensor parameters, including the working potential, pH, and temperature, was investigated in detail. The proposed biosensor showed a linear range of 5 × 10^?5 to 2 × 10^?2 M with a detection limit of 0.3 μM, a sensitivity of 25.9 mA mM^?1 cm^?2, and a current response time less than 20 s under the optimized conditions. The apparent Michaelis–Menten constant together with the apparent activation energy indicated that the proposed biosensor exhibited a high bioaffinity and a good enzyme activity. In addition, the biosensor also showed good operational and storage stabilities. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electrochemical sensing of NADH on NiO nanoparticles-modified carbon paste electrode and fabrication of ethanol dehydrogenase-based biosensor

In this work, an electrochemical β-nicotinamide adenine dinucleotide (NADH) sensor based on a carbon paste electrode modified with nickel oxide nanoparticles (NiONPs) was developed. The key highlights of this work are ease of preparation of the NiONPs-modified carbon paste electrode (NiONPs/MCPE), and its high sensitivity to NADH. The electrochemical characterization of NiONPs/MCPEs was performed via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical oxidation response of NADH was investigated by differential pulse voltammetry and chronoamperometry. The results indicated that the electrocatalytic effects of NiONPs on the response current of NADH significantly facilitated the electron transfer and improved the performance of the biosensor. Compared to bare carbon paste electrode (BCPE), the oxidation potential was shifted toward more negative potentials and the oxidation current was increased remarkably. Under optimum conditions, NADH could be detected in the range from 1.0 × 10^?4 to 1.0 mmol L^?1 with lower detection limit (0.05 μmol L^?1). The proposed NADH sensor demonstrated fast and reproducible response. Furthermore, an ethanol biosensor was prepared using NiONPs and NAD⁺-dependent alcohol dehydrogenase enzyme giving linear responses over the concentration range of 1.6 and 38 mmol L^?1 of ethanol.     

Preparation of a polymer containing indole groups by RAFT polymerization and one‐phase synthesis of AuNPs‐polymer nanocomposites

A one‐phase synthesis of AuNPs‐polymer nanocomposites using HAuCl₄ as the precursor is reported in this article. A flexible polymer, poly(2‐(4‐(di(1H‐indol‐3‐yl)methyl)phenoxy) ethyl methacrylate) (PMPEM), containing indole groups on the side chain was utilized as both a reducing reagent and soft template in the system. The PMPEM‐Au nanocomposites with three different sizes of AuNPs (25–50, 2, and 5 nm) were obtained just through choosing different solvents such as toluene, tetrahydrofuran (THF), and N,N‐dimethylformamide, respectively. Nanocomposites including the size of 25–50 and 2 nm AuNPs showed strong NLO absorption and refraction behaviors. The nonlinear refractive index n₂ of PMPEM‐Au nanocomposites prepared in toluene and THF were 9.35 × 10^?11 and 1.85 × 10^?10 m²/W, third‐order susceptibility χ⁽³⁾ were 2.55 × 10^?11 and 4.26 × 10^?11 esu, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013