Thin Layer Of Polyaniline Research Articles

Biotemplated top-down assembly of hybrid Ni nanoparticles/N doping carbon on diatomite for enhanced catalytic reduction of 4-nitrophenol

Biotemplated top-down assembly of hybrid Ni nanoparticles/N doping carbon on diatomite (DE/Ni/N-C) was synthesized and used to catalytically reduce 4-nitrophenol (4-NP) solution in presence of NaBH4. The uniform nickel silicate nanosheets uniformly grown on the diatomite with maintained porous structure, enlarging the specific surface area. The thin polyaniline layer was then controllably coated on the nickel silicate nanosheets. The well-dispersed Ni nanoparticles with mean diameter of 20.3 nm were reduced from nickel silicate nanosheets by carbon from polyaniline pyrolysis process. Meanwhile, the N doping carbon layer was in-situ generated outside of the Ni nanoparticles. In the catalytic reduction of 4-NP reaction, the DE/Ni/N-C-800 exhibited excellent catalytic activity with activity parameter 0.053 mg−1 s−1 and stability after ten cycles. The presented results show an enhanced catalytic behavior of the DE/Ni/N-C-800 prepared by the low-cost material and simple controllable process, which indicates their potential for environmental remediation applications.

Electrochemical Aptasensor with Layer‐by‐layer Deposited Polyaniline for Aflatoxin M1 Voltammetric Determination

AbstractMycotoxins are highly toxic metabolites of some fungi that frequently contaminate water, food and feed and hence cause several human and animal diseases. In this work, a new approach to the fast and reliable determination of aflatoxin M1 (AFM1) in water and milk has been proposed with reagent free protocol of signal measurement. For this purpose, DNA aptamer selective to AFM1 was entrapped between two thin layers of polyaniline (PANI) electrodeposited on glassy carbon electrode. The incubation of the aptasensor in the AFM1 solution results in remarkable decrease of the PANI intrinsic activity monitored by direct current voltammetry or electrochemical impedance spectroscopy. Appropriate calibration curves were linear in the range from 3 to 90 ng/L with limit of detection (LOD) 1–5 ng/L depending on the measurement mode. Mechanism of signal generation involves shielding electrostatic interactions between the PANI and aptamer in the surface layer and variation of its redox activity attributed to the emeraldine form of PANI. Selectivity of the response was proved by similar experiments with aflatoxin B1 and ochratoxin A and by comparison of the results with those obtained with non‐specific aptamer in the sensing layer. Simple protocol for milk pretreatment has been proposed for reliable detection of AFM1 on the level of its threshold limited values (20 ng/L).

Polyaniline enfolded hybrid carbon array substrate electrode for high performance supercapacitors

Abstract Composites with thin layers of polyaniline (PANI) draped on the surface of a hybrid carbon (HC) array or assemblage were prepared by the oxidative polymerization route. The carbon array substrate is a consistent network architecture of carbon nanotubes and graphene, with the benefit of elevated conductivity and surface area of the carbon components. The exceptional improved electrochemical performances of PANI enfolded HC array electrodes are due to the synergistic effect of the pseudocapacitance of PANI and the electric double layer capacitance of the carbon array. The supercapacitive characteristics of composite materials were inspected by using cyclic voltammetry, the galvanostatic charge-discharge test and electrochemical impedance analysis. The 025PANI-HC composite sample revealed a maximum specific capacitance of 1397.82 F g−1 at a scan rate of 5 mV s−1 and 1430 F g−1 at 1 A g−1 from galvanostatic charge-discharge data, respectively, in 1 m H2SO4. The composites exhibited a much larger specific capacitance value than pristine PANI. Also, the 025PANI-HC electrode had an unwavering operation and its specific capacitance retention was 89%, even after 5000 charge-discharge cycles at 1 A g−1.

Fabrication of conducting polymer modified CdS photoanodes for photoelectrochemical cell

The present work focuses on the modification of a spray deposited nanostructured CdS thin films by thin layers of polyaniline (PANI) and polypyrrole (PPY) systems using electro-polymerization method. The deposition of the conducting polymer on the CdS/FTO (Fluorine doped tin oxide) film surface has been validated by X-ray diffraction, UV–Vis spectrometry and Fourier transform infrared spectrometry. As deposited PANI and PPY films exhibit a bandgap of 2.0 eV and 1.7 eV, respectively. Optimization of deposition parameters viz. applied field, concentration of monomer and pH of the precursor has been performed to obtain a uniform and an adherent coating over CdS surface. The absorption band-edge of CdS is not shifted due to its surface modification via. PANI and PPY. However coating of PANI enhanced the visible light absorption capacity of CdS. This additionally ensures that there exists a thin polymer coating over CdS. The photocurrent of CdS/PANI and CdS/PPY is found to be enhanced by 3.2 and 2.6 times as compared to the bare CdS. An improvement in the PEC performance could be attributed to the favorable band energetics between the conjugated polymers and CdS that effectively reduces the recombination process and thus enhances the charge transfer process.

Characterization and Photocatalytic Activity of TiO<sub>2</sub>(rod)-SiO<sub>2</sub>-Polyaniline Nanocomposite

A study of TiO2(rod)-SiO2 composites coated with polyaniline (PANI) has been performed. PANI was synthesized through in-situ polymerization of aniline at various concentration (0.0137, 0.0274, and 0.0411 M) on the composite under acidic condition. PANI was confirmed by the appearance of C=N, C=C vibrations and the redshift of the band-gap from 3.14 eV for the TiO2(rod)-SiO2 into 3.0 eV for the TSP01 composite. It is also shown that the polymerization does not change the crystal structure of TiO2(rod)-SiO2 as confirmed by the XRD pattern. The TEM image shows a mixed structure of SiO2 coated by TiO2(rod)-PANI layers and the oxides coated by PANI layers. Therefore, the surface area of the resulted TiO2(rod) and the composites did not change significantly. The T TiO2(rod)-SiO2-PANI composite give small improvement under visible irradiation from 20.25 to 25.59% (around 5% from the bulk of TiO2(rod)) and from 25.03 to 25.59% (around 2% from TiO2(rod)-SiO2 composite). The mixed structure of the composites, as well as the formation of excessive layers of PANI, are possibly the case for the low photoactivity. Further improvement to obtain a core-shell structure with a thin layer of PANI is still sought.

Structure and properties of polyaniline nanocomposite coatings containing gold nanoparticles formed by low-energy electron beam deposition

Abstract Highly ordered conductive polyaniline (PANI) coatings containing gold nanoparticles were prepared by low-energy electron beam deposition method, with emeraldine base and chloroauric acid used as target materials. The molecular and chemical structure of the layers was studied by Fourier transform infrared, Raman, UV–vis and X-ray photoelectron spectroscopy. The morphology of the coatings was investigated by atomic force and transmission electron microscopy. Conductive properties were obtained by impedance spectroscopy method and scanning spreading resistance microscopy mode at the micro- and nanoscale. It was found that the emeraldine base layers formed from the products of electron-beam dispersion have extended, non-conductive polymer chains with partially reduced structure, with the ratio of imine and amine groups equal to 0.54. In case of electron-beam dispersion of the emeraldine base and chloroauric acid, a protoemeraldine structure is formed with conductivity 0.1 S/cm. The doping of this structure was carried out due to hydrochloric acid vapor and gold nanoparticles formed by decomposition of chloroauric acid, which have a narrow size distribution, with the most probable diameter about 40 nm. These gold nanoparticles improve the conductivity of the thin layers of PANI + Au composite, promoting intra- and intermolecular charge transfer of the PANI macromolecules aligned along the coating surface both at direct and alternating voltage. The proposed deposition method of highly oriented, conductive nanocomposite PANI-based coatings may be used in the direct formation of functional layers on conductive and non-conductive substrates.

Boronate-affinity based magnetic molecularly imprinted nanoparticles for the efficient extraction of the model glycoprotein horseradish peroxidase

Magnetic molecularly imprinted nanoparticles (MMIPs) with improved dispersity and an increased number of adsorption sites are described. Uniform silica layers were first deposited on the surface of Fe3O4 nanoparticles (Fe3O4 NPs) in order to improve the dispersity of magnetic nanoparticles. Then, 4-formylphenylboronic acid (FPBA) as functional monomer was immobilized on the magnetic carriers to improve the efficiency of template eluting and rebinding. A thin layer of polyaniline imprinted with horseradish peroxidase (HRP) as a model glycoprotein was then placed on the magnetic nanoparticles to enhance the dispersity of the resultant MMIPs. These exhibit high adsorption capacity (62 mg g−1), a satisfactory imprinting factor ( 3.78) and short adsorption equilibrium time (40 min) toward HRP, and the limit of detection is 18.7 μg L−1. This kind of MMIPs, therefore, is deemed being a useful tool for extracting low-abundance glycoproteins from even complex samples.

Fully-Polymeric pH Sensor Realized by Means of a Single-Step Soft Embossing Technique.

We present here an electrochemical sensor microsystem for the monitoring of pH. The all-polymeric device is comprised of a cyclic olefin copolymer substrate, a 200 nm-thin patterned layer of conductive polymer (PEDOT), and a 70 nm electropolymerized layer of a pH sensitive conductive polymer (polyaniline). The patterning of the fluidic (microfluidic channels) and conductive (wiring and electrodes) functional elements was achieved with a single soft PDMS mold via a single embossing step process. A post-processing treatment with ethylene glycol assured the functional enhancement of the electrodes, as demonstrated via an electrical and electrochemical characterization. A surface modification of the electrodes was carried out, based on voltammetric electropolymerization, to obtain a thin layer of polyaniline. The mechanism for pH sensing is based on the redox reactions of the polyaniline layer caused by protonation. The sensing performance of the microsystem was finally validated by monitoring its potentiometric response upon exposure to a relevant range of pH.

Synthesis of polyaniline shell on nickel oxide nanoflake arrays for enhanced lithium ion storage

Developing conducting polymer/oxide composites are of great importance to construct advanced electrochemical devices. In this work, we report a successive electrodeposition methods to fabricate polyaniline (PANI) on nickel oxide (NiO) nanoflake forming composite core-shell arrays. A thin layer of PANI of ∼10nm is successfully coated on the surface of NiO nanoflake core. High porosity and enhanced conductivity are obtained in this composite electrode. As anode materials for lithium ion batteries, the NiO/PANI core-shell arrays exhibit weaker polarization and better cycling performance as compared to the bare NiO film. The second discharge capacity of NiO/PANI composite arrays is about 780mAhg−1 at 0.1Ag−1, higher than that of the bare NiO film (679mAhg−1). The improvements of the electrochemical properties are attributed to the PANI, which forms a uniform conductive network leading to improved electrochemical performance.

Supercritical Carbon Dioxide-Assisted Process for Well-Dispersed Silicon/Graphene Composite as a Li ion Battery Anode.

The silicon (Si)/graphene composite has been touted as one of the most promising anode materials for lithium ion batteries. However, the optimal fabrication method for this composite remains a challenge. Here, we developed a novel method using supercritical carbon dioxide (scCO2) to intercalate Si nanoparticles into graphene nanosheets. Silicon was modified with a thin layer of polyaniline, which assisted the dispersion of graphene sheets by introducing π-π interaction. Using scCO2, well-dispersed Si/graphene composite was successfully obtained in a short time under mild temperature. The composite showed high cycle performance (1,789 mAh/g after 250 cycles) and rate capability (1,690 mAh/g at a current density of 4,000 mA/g). This study provides a new approach for cost-effective and scalable preparation of a Si/graphene composite using scCO2 for a highly stable lithium battery anode material.

Covalently bonded reduced graphene oxide/polyaniline composite for electrochemical sensors and capacitors

Polyaniline grafted reduced graphene oxide (RGO-g-PANI) composites were synthesized via a facile and efficient two-step method. RGO was first surface-modified with 1,3-diaminopropane, which provided reactive NH2 groups that can polymerize with aniline, and then grafted with polymer chains. The analysis results showed that the surface of the RGO sheets was covered with a smooth thin layer of polyaniline. The as-prepared composites were used to modify the glass carbon electrodes for the chemical detection of hydrogen peroxide in aqueous solutions. The response to H2O2 was linear in the range, 0.05 to 14 μM (R2 = 0.995), and the detection limit was 0.37 μM (at an S/N of 3). In addition, the specific capacitance of the obtained composite was as high as 1337 F g− 1 at a very high current density of 15 A g− 1, highlighting its promising applications as an efficient electrode material for supercapacitors.

The Effect of Electrodeposited PANI on Corrosion Behavior of 316 Stainless Steel Coated by CVD Grown MWCNTs under PEMFC Bipolar Plate Working Condition

Polyaniline (PANI) electrodeposition on bare and carbon nanotube (CNT) coated 316 SS was carried out using a cyclic voltammetry (CV) electropolymerization method in diluted H2SO4 media containing aniline monomer. CNTs were grown in a thermal CVD reactor on 316 SS either by direct growth using ethylene precursor or by continuous feeding of an external catalyst, ferrocene, dissolved in toluene as the carbon precursor. Corrosion behavior of the coated materials was assessed by potentiodynamic and potentiostatic methods in an attempt to simulate the working conditions of proton exchange membrane fuel cell (PEMFC) bipolar plates. While a thick PANI coating could not provide a protective barrier to either bare or CNT coated 316 SS samples, a sensible improvement in corrosion resistance was revealed in the presence of a thin PANI layer. However, the protective capability of the PANI thin film was still inadequate for the purpose of providing reasonable corrosion resistance to the material under simulated PEMFC conditions, due to severe deterioration of CNT coated 316 SS caused by the initial carbon treatment.

Thin nanocomposite layers based on a complex of polyaniline and graphene

Two techniques of manufacturing a nanocomposite based on a complex of polyaniline with polymer acid and graphene are proposed. The electric conductivity of thin nanocomposite layers is higher than that of a polymer complex of polyaniline and strongly depends on the degree of oxidation of graphene. An explanation of the effect is suggested that takes into account electron interactions between the graphene planes and polyaniline backbone, as well as the possibility of formation of hydrogen bonds between functional groups of semioxidized graphene and polyacid. The results of surface topography analysis for thin layers of polyaniline and nanocomposite agree well with the regularities of the structure of each layer that are due to the above interactions between graphene and the polymer complex.

Facile Preparation of Glycoprotein-Imprinted 96-Well Microplates for Enzyme-Linked Immunosorbent Assay by Boronate Affinity-Based Oriented Surface Imprinting

Molecularly imprinted polymers (MIPs), as inexpensive and stable substitutes of antibodies, have shown great promise in immunoassays. Glycoproteins are of significant diagnostic value. To facilitate the application of MIPs in clinical diagnostics, a general and facile imprinting method toward glycoproteins oriented for an enzyme-linked immunosorbent assay (ELISA) in the form of a 96-well microplate is essential but has not been fully explored yet. In this study, a new method called boronate affinity-based oriented surface imprinting was proposed for facile preparation of glycoprotein-imprinted microplates. A template glycoprotein was first immobilized by a boronic acid-modified microplate through boronate affinity binding, and then, a thin layer of polyaniline was formed to cover the microplate surface via in-water self-copolymerization. After the template was removed by an acidic solution, 3D cavities that can rebind the template were fabricated on the microplate surface. Using horseradish peroxidase (HRP) as a model target, the effects of imprinting conditions as well as the properties and performance of the prepared MIPs were investigated. α-Fetoprotein (AFP)-imprinted microplate was then prepared, and thereby, a MIP-based ELISA method was established. The prepared MIPs exhibited several highly favorable features, including excellent specificity, widely applicable binding pH, superb tolerance for interference, high binding strength, fast equilibrium kinetics, and reusability. The MIP-based ELISA method was finally applied to the analysis of AFP in human serum. The result was in good agreement with that by radioimmunoassay, showing a promising prospect of the proposed method in clinical diagnostics.

Improved charging/discharging behavior of electropolymerized nanostructured composite films of polyaniline and electrochemically reduced graphene oxide

In this work, a simple electrochemical reduction procedure has been applied to nanostructured composite films of polyaniline (PANI) and graphene oxide (GO) having a globular surface morphology with the grain size of 50nm. The reduction converts GO to reduced GO (rGO) which improves the electroactivity of the PANI composite films with 30%. Cyclic voltammetry confirmed the reduction of GO to rGO whereas electrochemical impedance spectroscopy showed that the rGO network increases the redox capacitance of the composite films with 15% to 77mFcm−2. In a three-electrode cell, the anodic charge of the PANI film containing GO increased with 18.7% during the potential cycling stability test for 10,000 cycles between −0.2 and 0.5V, indicating that the film had a good stability against degradation. This composite film type still maintained a high capacitance of 15mFcm−2 in a symmetric two-electrode cell after 10,000 potential cycles between 0 and 0.4V. The electrochemically prepared PANI composite films reported here are aimed to be used in capacitor applications where it is crucial to deposit thin PANI layers on well-defined small surfaces where other polymerization or deposition techniques cannot be used and in solid-state chemical sensors as ion-to-electron transducer interfaces.

Physicochemical properties of silica gel coated with a thin layer of polyaniline (PANI) and its application in non-suppressed ion chromatography

Physicochemical properties of a new sorbent and its potential application in non-suppressed ion chromatography (IC) have been investigated. The sorbent was obtained in a process of covering silica gel particles with a film of polyaniline (PANI).The properties of silica modified with polyaniline such as particle size, porosity, average quantity of polyaniline covering carrier and density of sorbent were determined. In our study the following methods were used: microscopic analysis, laser diffraction technique, combustion analysis, mercury porosimetry and helium pycnometry. Column with the newly obtained packing was used for the separation of inorganic anions. Optimized chromatographic system was successfully employed for analysis of iodide and bromide in selected pharmaceutical products (Bochnia salt and Iwonicz salt) applied in chronic respiratory disease. Analysis was carried out using 0.1M solution of HCl in mixture of methanol/water (50:50v/v) as a mobile phase; the flow rate was 0.3mLmin−1, temperature was 24°C and λ=210nm. Validation parameters such as correlation coefficient, RSD values, recovery, detection and quantification limits were found to be satisfactory.

A Polyaniline-Coated Integrated Microfiber Resonator for UV Detection

We present a UV detector based on an integrated microfiber resonator. In fabrication, a thin layer of polyaniline (PAni) is deposited on a ~1-mm-diameter microfiber ring resonator-the sensing region of the detector. Red shift is observed in the output spectrum when PAni is irradiated with a UV light with a peak wavelength at 365 nm. This phenomenon can be due to the high absorbance in the UV region and photothermal effect of PAni. The wavelength shift is linearly proportional to the UV light intensity and the measured sensitivity is 6.61 nm/(W·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ).

Electrochemical property of graphene oxide/polyaniline composite prepared by in situ interfacial polymerization

Graphene oxide–polyaniline composites were synthesized by an interfacial method using two green solvents, water and an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate), as the two phases. The interfacial polymerization of aniline was carried out at room temperature in the presence of graphene oxide dispersed in the aqueous phase. The analysis revealed the surface of the graphene sheets to be coated with a smooth thin layer of polyaniline. The thermal stability of the composites was much better than that of bare graphene oxide. The composites were used to modify the glass carbon electrodes for the chemical detection of hydrogen peroxide in aqueous media. This method is a facile, efficient, and green route for the development of doped polyaniline materials suitable for chemical sensors.

Asymmetric hybrid capacitors based on activated carbon and activated carbon fibre–PANI electrodes

Composites consisting of polyaniline (PANI) coatings inside the microporosity of an activated carbon fibre (ACF) were prepared by electrochemical and chemical methods. Electrochemical characterization of both composites points out that the electrodes with polyaniline show a higher capacitance than the pristine porous carbon electrode. These materials have been used to develop an asymmetric capacitor based on activated carbon (AC) as negative electrode and an ACF–PANI composite as positive electrode in H2SO4 solution as electrolyte. The presence of a thin layer of polyaniline inside the porosity of the activated carbon fibres avoids the oxidation of the carbon material and the oxygen evolution reaction is produced at more positive potentials. This capacitor was tested in a maximum cell voltage of 1.6V and exhibited high energy densities, calculated for the unpackaged active materials, with values of 20Whkg−1 and power densities of 2.1kWkg−1 with excellent cycle lifetime (90% during the first 1000 cycles) and high coulombic efficiency.

Properties of Chelating Sorbent Prepared by Modification of Silica Gel with Polyaniline and Acid Alizarin Violet N

A new chelating sorbent was prepared, by synthesizing the surface of silica gel with a very thin layer of polyaniline, and then the thus obtained carrier was impregnated with Acid Alizarin Violet N. The stability of the resulting chelating sorbent and the sorption of selected metal ions was investigated. The sorbent was used for the purification of tap water and distilled water from some heavy metal ions and for additional purification of aqueous solutions of KCl from trace amounts of heavy metals. An effective method of regenerating the column with the chelating sorbent obtained is proposed. For regeneration 5% aqueous ammonia solution was used; then the column had to be conditioned with hydrochloric acid. It was found that the method does not destroy the sorbent skeleton.