Poly N-methylpyrrole Research Articles

NiSe integrated with polymerized reduced carbon sheet: As an effective electrocatalyst for methanol oxidation reaction

A low-energy approach was used to create ternary composites of hollow tubular Poly-N-methyl pyrrole (P-NMPy) and NiSe nanoparticles decorated onreduced graphene oxide (RGO). On the surface of RGO, P-NMPy, and NiSe nanoparticles were uniformly disseminated. The RGO/NiSe@P-NMPy (RNP) polymer nanocomposite was made utilizing a straightforward chemical oxidative process. The RGO/NiSe@P-NMPy nanocomposite was studied using FTIR spectroscopy, UV–visible, XRD, FE-SEM with EDAX, AFM, TEM and electrochemical investigations. The electrocatalytic activity of this polymer nanocomposite for the methanol oxidation reaction in alkaline environments was validated using cyclic voltammetry. The RGO/NiSe@P-NMPy electrocatalyst shows excellent electrocatalytic activity, lower oxidation potential (0.1 V), improved current density (127 mA/cm2), excellent stability and longevity (900 s) towards methanol oxidation reaction (MOR) in alkaline medium. It was observed RGO/NiSe@P-NMPy electrocatalyst, the ECSA value is 70.83 m2/g. This result clearly depicts that RGO/NiSe@P-NMPy electrocatalyst has more active sites for MOR reaction. According to the results, the P-NMPy introduction in RGO/Nickel Selenide structure can enhance the performance of methanol oxidation and increase the resistance to CO in comparison with monometallic catalysts.

Sol-Gel Synthesis and Characterization of Highly Selective Poly(N-methyl pyrrole) Stannous(II)Tungstate Nano Composite for Mercury (Hg(II)) Detection

The sol-gel process was used to create a new type of polypyrrole-Stannous(II)tungstate nanocomposite by poly(N-methyl pyrrole (PNMPy) sol in Stannous(II)tungstate gel, produced separately using sodium silicotungstic acid and Tn(II)chloride. Tin(II)tungstate (SnWO3) was made by changing the mixing volume ratios of SnWO3 and with a constant amount of an organic polymer. The composite was characterized by TGA, XRD, FTIR, and SEM measurements. A commercially available glassy carbon electrode (GCE) was modified with PNMPy/nano-Stannous(II)WO3 nanocomposites to create a chemical sensor for selective detection of Hg2+ ions using an effective electrochemical methodology. In the I-V technique, selectively toxic Hg2+ ion was targeted selectively, which shows a rapid reaction toward PNMPy/nano-Stannous(II)WO3/Nafion/GCE sensor. It also demonstrates long-term stability, an ultra-low detection limit, exceptional sensitivity, and excellent reproducibility and repeatability. For 0.1 mM to 1.0 nM aqueous Hg2+ ion solution, a linear calibration plot (r2: 0.9993) was achieved, with a suitable sensitivity value of 2.8241 AM−1 cm−2 and an extraordinarily low detection limit (LOD) of 3.40.1 pM (S/N = 3). As a result, the cationic sensor modified by PNMPy/nano-Stannous(II)WO3/GCE could be a promising electrode.

The effect of supporting electrolyte concentrations on the growth of nickel nanostructures

Nickel nanostructures (Ni NSs) were grown on poly N-methyl pyrrole (PMPy) surface via facile electrochemical deposition method. Morphology and crystalline properties of the fabricated Ni NSs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and cyclic voltammetry (CV). The size-strain plot model was employed to determine the average crystallite sizes of Ni NSs prepared at 0.001, 0.01 and 0.1 M of KCl concentrations, respectively. Results indicated that Ni NSs morphologies were influenced by the concentration of KCl electrolyte in which utilized as supporting electrolyte. The average crystallite size decreased as the KCl electrolyte concentration increased. An irregular structure consisting of microspheres with an average size of 2 µm, nanodendritic structure with an average thickness of 120 nm and a large-scale uniform nanowall structure with an average thickness of 70 nm were formed in the presence of 0.001, 0.01 and 0.1 M KCl concentrations, respectively. The electrochemical behavior of Ni NSs characterized by cyclic voltammetry (CV) in 1 M solution of KOH revealed an improvement in the redox reaction of the Ni nano wall (Ni NW) compared to other Ni NSs electrodes, thus making Ni NW a good candidate for future utilization in electrode materials of fuel cells.

Electroactive polymers for the detection of morphine

The interaction between morphine (MO), a very potent analgesic psychoactive drug, and five electroactive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-methylthiophene) (P3MT), polypyrrole (PPy), poly(N-methylpyrrole (PNMPy) and poly[N-(2-cyanoethyl)pyrrole] (PNCPy), has been examined using theoretical calculations on model complexes and voltammetric measures considering different pHs and incubation times. Quantum mechanical calculations in model polymers predict that the strength of the binding between the different polymers and morphine increases as follows: PEDOT PNMPy) and neutral (P3MT ≈ PNCPy) pHs. Energy decomposition analyses of the interaction of MO with different model polymers indicate that the stronger affinity of MO for P3MT and PNCPy as compared to PEDOT, PNMPy, and PPy is due to more favorable orbital interactions. These more stabilizing orbital interactions are the result of the larger charge transfer from MO to P3MT and PNCPy model polymers that takes place because of the higher stability of the single occupied molecular orbital (SOMO) of these model polymers. Therefore, to design polymers with a large capacity to detect MO we suggest looking at polymers with high electron affinity.

Performance variation of Li rechargeable cells having polypyrrole cathodes doped with different anions

Electrochemically synthesized polymers such as polypyrrole (PPy), polyaniline (PANI) and polyNmethyl pyrrole (PNMP) are considered as one of the most promising polymer electrode material groups for the development of advanced electrochemical devices such as electrochemical cells, super capacitors, electrochromic devices and solar cells. The properties of electrochemically synthesized polymers are known to be largely dependent on the dopant anion used and hence, their performance in applications also depend greatly upon the dopants. In this study, the role of the anion used to dope the PPy cathode on the performance of a lithium (Li) rechargeable cell is reported. Anions were varied from small inorganic anions (CF3SO3 -) to large anions (alkilsulphonate, AS- and dodeclybenzenesulphonate, DBS-). PPy was electropolymerized and the cells were fabricated with a polyacrylonitrile (PAN) based solid polymer electrolyte (SPE) while Li served as the anode. Cyclic voltammetry and continuous charge discharge tests were carried out to characterize the cells. The cycling results showed better cycling charge and long cycle life with the cells fabricated with PPy doped with large anions. The cells with large anions showed higher cycle numbers while the cells with inorganic anions could not be cycled over 350 cycles. Even with electrodes having larger anions, better results can be obtained with slow scan rates. Scanning electron microscopy (SEM) studies revealed that electrodes have a porous morphology with smaller anions and a dense morphology with larger anions, which also affect the performance variations. DOI: http://dx.doi.org/10.4038/jnsfsr.v42i2.6997 J.Natn.Sci.Foundation Sri Lanka 2014 42 (2): 143-147

In situ spectroelectrochemistry, electrosynthesis and growth rates of conducting polypyrrole and poly N-methylpyrrole on gold and indium tin oxide glass modified by thiolated α-cyclodextrin self-assembled monolayer’s (SAMs)

Electrochemical synthesis, in situ spectroelectrochemistry and growth rates of conducting polypyrrole (PPy) and poly(N-methylpyrrole) (PNMPy) on bare and modified gold and indium tin oxide (ITO) glass with thiolated α-cyclodextrin (T-α-CD) self-assembled monolayers (SAMs) have been investigated. The films modifiers of functionalized SAMs were characterized by means of CV, in situ UV–visible spectroscopy, in situ conductivity measurement and scanning electron microscopy (SEM). The polymerization reactions are 0.73 and 0.81 orders with respect to the pyrrole and N-methylpyrrole concentrations and 0.61 and 0.64 orders with respect to the amount of PPy and PNMPy. The kinetic results indicate that the polymerization growth rate of PPy is faster than PNMPy. However, the polymerization growth rates of both polymers at the modified electrodes SAMs are slower than that at bare gold electrode. The in situ conductivity of the polymers on bare and modified gold electrodes have been studied. The results indicates that the in situ conductivity of polymers on modified gold electrode were lower by around 1–2 orders of magnitude than those of polymers on bare gold electrodes. The in situ UV–visible spectroscopy of polymers on modified ITO/glass with T-α-CD-SAMs indicates a characteristic absorption’s bands. Scanning electron microscopic photos reveal that the T-α-CD may act as molecular templates for electrochemical polymerization of conducting PPy and PNMPy.

In Situ UV-Visible Spectroelectrochemistry and Cyclic Voltammetry of Conducting N-Methylpyrrole: Indole Copolymers on Gold Electrode

Electrochemical copolymerization of N-methylpyrrole (NMPy) and indole (In) in various monomer ratios were carried out by potentiodynamically methods in acetonitrile electrolyte containing LiClO4 on gold electrode. The obtained homopolymers and copolymers were characterized with cyclic voltammetry (CV), in situ UV-Visible, FT-IR spectroscopy, scanning electron microscopy (SEM) and in situ resistivity measurements. The cyclic voltammetry study shows that the onset potential for the monomers and co monomers curves is located at the different values for N-methylpyrrole, indole and N-methylpyrrole-indole. There is a nucleation process followed by growth of nuclei to continuous films. The oxidation and reduction peaks for copolymer, P(NMPy-In), which synthesized from the 1:1 mole-mole ratio concentration of the relevant monomers, located between those for poly N-methylpyrrole (PNMPy) and polyindole (PIn) films. The observed values were showed a decreased [NMPy]/[In] ratio concentration in the copolymers shifts the peak potential to more positive. The in situ UV-Visible, FT-IR spectroscopy and SEM analysis of homopolymers and copolymers were also studied. The result shows the intermediate spectroscopic properties between homopolymers and copolymers. The in situ resistivity measurements showed that the copolymers have a lower conductivity than the corresponding parent homopolymers.

Electrochemical synthesis of N-methyl and 3-methyl pyrrole perchlorate doped copolymer films

Electrochemical copolymerization of 3-methylpyrrole and N-methylpyrrole perchlorate doped has been carried out at two overpotentials and at different electrodeposition times in acetonitrile medium. A mixture of instantaneous and progressive nucleation mechanisms has been established from the current density–time transients. Doping/dedoping reversibility is deduced from the electrochemical study of copolymer films by cyclic voltammetry. Fourier Transform Infrared spectrum analysis shows that electropolymerization time has a great influence on the random monomers proportion in the copolymer obtained. Although the copolymer conductivity is in the range of the measured for poly 3-methylpyrrole and poly N-methylpyrrole obtained in similar conditions, it remains conductive for a much longer time than the homopolymers.

Proton acid doping and conductivity decay of poly N-methylpyrrole

A study of conducting poly N-methylpyrrole (PNMPy)/ClO 4 films electrochemically synthesized in acetonitrile solution has been carried out. Films immersed in aqueous solutions of increasing pH were examined by FTIR spectroscopy. The IR spectrum, yellow color, and low conductivity indicate that polymer changes to the non-conducting form in basic medium. However, film conductivity is recovered after a new immersion in acid solution. This points to the existence of a proton doping mechanism in PNMPy/ClO 4 confirmed by the infrared spectrum and by the conductivity changes observed after acid immersion. However no new NH or CH bonds are observed in the spectra of these films, which indicates that protons in the film seem to be “free”. Stabilization in air of basic-acid treated films is observed since conductivity of these films remains higher than 10 −4 S cm −1 for more than 400 h. Conductivity decay with ageing time has also been determined as a first order process with kinetic constants k 1=(0.03±0.01) h −1 during the first 50 h and k 2=(0.0037±0.0003) h −1 for there up to 450 h.

Influence of counter-ion concentration on properties of electrochemically generated poly- N-methylpyrrole (PNMPy/ClO 4)

This is a study of the relationship observed between the synthesis conditions and polymer properties in electrochemically generated poly- N-methylpyrrole (PNMPy). The best values are given for overpotentials of synthesis and perchlorate concentration that provide a polymer with improved conductivity and electrochemical properties. In this way a film was obtained with a conductivity of 1.3 S m −1. The morphology, electronic spectrum and stability of the film were determined. An equation was determined relating film thickness and polymerization charge density.

The influence of preparation conditions on the electrical conductivity of poly- N-methylpyrrole films

Electro-active poly- N-methylpyrrole (PNMP) films have been galvanostatically polymerized under a range of conditions. The influence of the conditions used in electropolymerization, such as electrolyte concentration, current density, type of doping anion, and temperature during polymerization on the electrical conductivity has been investigated. The conductivity was measured by the in situ method using a specially prepared two-band microelectrode. The current density used during the polymerization has a considerable influence on the conductivity, as earlier observed for polypyrrole in non-aqueous electrolytes. The conductivity changes with the size of the anion and the concentration of the electrolyte as well as on the temperature at which the polymerization was carried out. Polymer films formed at relatively higher temperatures had lower conductivities and were not able to insert as many counterions, indicating that the films formed were less perfect. At higher temperatures the increased rates and numbers of side reactions may be competing with the ideal one-dimensional polymerization process.

Electrical Properties of Polypyrrole and Poly N-Methylpyrrole Organised in Manganic-Stearate Template in Langmuir Blodgett Films

Abstract The electrical properties of Langmuir-Blodgett (LB) films of polypyrrole and poly N-methylpyr-role fabricated on a manganic stearate template in the LB film has been studied. The LB films of polymer exhibit domains of highly organised two dimensional linear array of polymer granules sandwiched between insulating fatty acid layers along with some disorganised domains. Measured in-plane conductivity of polypyrrole and poly N-methylpyrrole are 1.5 S/cm and 0.012 S/cm with thermal activation energy 0.08 eV and 0.214 eV respectively. The transverse conductivity is 10−10 S/cm and 10−12 S/cm for polypyrrole and poly N-methylpyrrole respectively showing a high degree of anisotropy in both the LB films.

An electrochemical study of pyrrole/N-methylpyrrole copolymer

Electrochemical growth of polypyrrole (PPy), poly- N-methylpyrrole (PMePy) and PPy + PMePy copolymers in 0.5 M LiClO 4 + propylene carbonate was studied. The potential of the polymerization threshold increases with decreasing monomer concentration. Composition and redox properties of thin polymeric films were controlled by varying the polymerization potential in a narrow interval between the polymerization and overoxidation thresholds. Virgin copolymers grown from “dry” electrolytes ( $ ̃ 10 ppm H 2O) show two separate reduction peaks; copolymers grown from water-containing (1 vol.%) electrolytes show a single reduction peak. A correlation between the voltammetric peak potential and the available coulombic capacity of the copolymer was found. An increased [MePy]/[Py] ratio in the copolymer shifts the peak potential to more positive values but the reversible coulombic capacity decreases. Consequently, PPy + PMePy copolymer electrodes do not offer an increased energy density in batteries.

Influence of Dopant Ions on Dielectric and Physical Properties of Electrochemically Formed Poly‐N‐Methylpyrrole

Dielectric properties (dielectric constants, dielectric losses, conductivity, and voltage breakdown strengths) of electrochemically formed poly‐N‐methylpyrrole (PNMP) have been studied as a function of the anions used in aqueous supporting electrolyte during electrochemical polymerization. Depending on the electrolyte anion and synthesis conditions, dielectric properties of resulting PNMP films varied considerably.

Electronic and structural characteristics of five poly membered heterocycles (polythiophene, polypyrrole): An ultraviolet and x-ray photoelectron spectroscopy study

The electronic and structural properties of electrochemically synthetized five poly membered heterocycles [polypyrrole (PP), poly-N-methylpyrrole (PNMeP), polythiophene (PT), polybithiophene (PBT), and poly-3-methylthiophene (PMeT)] in their doped conducting and undoped semiconducting states have been determined by x-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS). A systematic evolution of the π bonding orbitals is observed by going successively from thiophene to bithiophene and to terthiophene which leads finally to the formation of an intrinsic π bonding band for the undoped polythiophene, located at 1.05 eV below the Fermi level Ef. This π bonding band is also detected with PP, PBT, and PMeT in good agreement with theoretical band structure calculations and implies a long range order along the polymeric chains. In contrast, PNMeP valence spectra exhibit broad features connected with the existence of structural defects and/or torsion angle between the monomeric units. Shake-up satellites are generally observed on the high binding energy side of the C1s, S2p (or N1s) core levels related to π→π* transitions. The S/C (or N/C) ratio is always very close to the predicted theoretical value which means that the structural architecture of the polymeric backbone is very similar to the monomer one. Upon ClO−4 doping, the π bonding band is extended up to ∼0.2 eV below Ef. Simultaneously, the bonding band intensity decreases, and the C1s, S2p, (or N1s) core level peaks become broad and asymmetric (PP, PMeT, PT). These evolutions are completely reversible during the doping–undoping processes, independent of the anion used (BF−4,SO3CF−3) and of the thickness of the film (20–1000 Å). These modifications are dramatically reduced with PNMeP although its doping level is as high as 30%. These UV photoelectron spectroscopy and x-ray photoelectron spectroscopy results combined with the near edge x-ray absorption fine structure (NEXAFS) characteristics give insight into the conduction mechanism inside these conducting polymers: Appearance of a metallic-like behavior due to first the extraction of electrons from the π bonding band, and second, an extension of the π and π* bands towards Ef narrowing the band gap from 2.1 eV in the undoped state to 0.3–0.4 eV in the doped form.

Effect of sulphate ion on the electrochemical polymerization of pyrrole and N-methylpyrrole

Pyrrole and N-methylpyrrole were electrochemically polymerized in an identical manner in aqueous electrolytes containing (Et 4N)BF 4, LiClO 4 or Na 2SO 4 to give films of the corresponding p-doped polymers. The polymer obtained from the aqueous Na 2SO 4 electrolyte, [(poly N-methylpyrrole) +y (SO 4) y/2 2-] x, differed from the other polymers in that it exhibited a very low conductivity (≈ 10 −7 S/cm), contained a high concentration of > C=O groups and had an EPR linewidth, Δ H pp, more than an order of magnitude greater than that found in the corresponding polymers obtained from the (Et 4N)BF 4 and LiClO 4 electrolytes. A sample of [(poly N-methypyrrole) +y(BF 4) y −] x electrochemically synthesized in CH 3CN and subsequently converted electrochemically to the corresponding sulphate in the Na 2SO 4 aqueous electrolyte exhibited normal behaviour. A mechanism is proposed for the introduction of > C=O groups into the poly( N-methylpyrrole) polymer during its electrochemical polymerization in the Na 2SO 4 aqueous electrolyte.

Polypyrrole and poly N-methylpyrrole — An electrochemical study in an aqueous medium

Polypyrrole (PP) and poly N-methylpyrrole (PMP) synthesized in acetonitrile solution containing 0.2 M LiClO 4 have been studied in an aqueous medium at different pH values by potentiometry at zero current, double pulse imposed current methods and cyclic voltammetry. The last was also used to determine the stability range. We observed from potential-pH measurements that PP has fairly good resistance towards sulphuric acid up to 4 M and shows less resistance towards strong basic media above pH 12. Cyclic voltammetry studies show that PP is more easily degraded at potentials greater than 1 V than in the less noble potential range. In the pH range studied, PP exchanges one proton for each electron. PP can exist in at least six forms and the exchange of the protons can precede or follow the electron exchange: two of these forms of PP can exist in oxidized and reduced forms without any counter anion. PMP presents a better stability from the electrochemical point of view, especially in a basic medium. Between pH 1 and pH 9.5 it exchanges only one proton for two electrons and above pH 9.5 two protons for one electron.