Chemical Oxidative Polymerization Of Pyrrole Research Articles

Improved Ethanol Sensing Performance of α-MnO2 Nanorods at Room Temperature Enabled through PPy Embedding.

Ethanol is a colorless, highly flammable, volatile organic compound and is a biomarker for fatty liver diseases. So, high-performance and reliable ethanol sensors are the need of the day for biomedical and environmental monitoring applications and drunken driving detection. In this work, we have reported a polypyrrole (PPy)-embedded α-MnO2 nanorod (NR)-based chemiresistive sensor for the selective detection of trace ethanol vapor at room temperature (25 °C). PPy-embedded α-MnO2 NR nanocomposites (MP25, MP50, and MP100) were synthesized by in situ chemical oxidative polymerization of pyrrole followed by mixing of α-MnO2 NR having different weight ratios. The prepared nanocomposites were characterized by various sophisticated instruments such as XRD, FTIR, Raman spectroscopy, BET, FESEM, TEM, EDX, UV-vis spectroscopy, and current-voltage (I-V) measurement. The as-prepared sensor, namely, PPy-embedded α-MnO2 nanorod (MP50), shows the highest response to ethanol vapor with a detection lower limit of 1 ppm at room temperature with rapid response (∼2.39 s) and recovery (∼37.08 s) times associated with at least 60 days stability, excellent selectivity, good repeatability, and reproducibility. The formation of a p-n heterojunction and transfer of charge carriers between PPy and MnO2 nanoparticles are attributed to the enhancement of sensing performance. Thus, the prepared sensor could be potentially applicable to detect ethanol content in alcoholic beverages, diagnose liver disease from exhale breath analysis, and drunken driving detection.

A study on surfactant modified polypyrrole nanostructures and its applications in supercapacitors

Nanocomposites of Polypyrrole (Ppy), were synthesized by chemical oxidative polymerization of pyrrole, in the presence of mono and mixed‐surfactant solutions using ammonium persulfate as an oxidant and were investigated for its applications in super capacitors. The surfactants used in the experiments included anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS) and cationic surfactants, tetradecyltrimethylammonium bromide (TTAB) as well as cetyltrimethylammonium bromide (CTAB). The morphology and structure of the resulting Ppy were investigated in detail with FESEM and FTIR, respectively. The addition of anionic surfactants produced globular morphology. The results showed that the interaction between the different surfactants and the interaction between the surfactants and the polymer influenced the morphology, structure and conductivity of the resulting polymer to different degrees. Apart from these, XRD, UV-Vis spectroscopy and cyclic voltammetry (CV) were also performed to characterize the prepared composites. In comparison with the results for mono surfactant solutions, the polymerization of pyrrole in mixed‐surfactant solutions shows significant changes in morphologies and electrochemical properties of Ppy. The results of CV show that the specific capacitance values of Ppy samples with anionic surfactants are greater than cationic surfactants. In case of mixed surfactants, sample with SDBS + TTAB posses highest specific capacitance of 204 Fg−1 at scan rate 100 mVs−1. The good electrochemical properties can be attributed to the highly porous structural advantage of the Ppy sample prepared using SDBS + TTAB. It indicates the energy holding capacity or capacitance of the prepared samples and can be utilized in sensing applications like supercapacitors.

Layer‐by‐layer preparation of electromagnetic NH2‐SiO2/polypyrrole/Ni nanocomposites, characterization and their electrochemical properties

AbstractCombinations of organic conducting polymers and inorganic electromagnetic materials have drawn much attention in various fields like energy storage materials, biosensors, biomedical applications, catalysis and removal of heavy metals from water. In this investigation an attempt is made to decorate polypyrrole (PPy), a semiconducting electroactive polymer, with Ni nanoparticles on a functional silica (SiO2) support. First, amine‐functionalized mesoporous NH2‐SiO2 seed particles are prepared by the sol–gel method using hexamethylenediamine as a surface‐functionalizing agent and cetyltrimethylammonium bromide as a template. Second, NH2‐SiO2/PPy composite particles are prepared via in situ seeded chemical oxidative polymerization of pyrrole. The surface of the NH2‐SiO2/PPy composite particles is finally immobilized/doped with Ni nanoparticles via in situ chemical reduction of Ni(II) salt. The surface morphology, structure modification, size distribution and magnetic properties of the prepared NH2‐SiO2/PPy/Ni nanocomposite particles are confirmed using various spectroscopic techniques, electron microscopy, Brunauer–Emmett–Teller measurements, X‐ray diffraction and vibrating sample magnetometry. The NH2‐SiO2/PPy/Ni nanocomposite particles possess good paramagnetic properties. A comparative study of electrochemical properties revealed improvement in specific capacitance of NH2‐SiO2/PPy composite compared to PPy but further decoration with Ni nanoparticles under alkaline condition reduces the capacitance value. © 2022 Society of Industrial Chemistry.

Adsorption of rhodamine-B by polypyrrole Sn (IV) tungstophosphate nanocomposite cation exchanger: Kinetic-cum-thermodynamic investigations

ABSTRACT Synthesis of an organic-inorganic polypyrrole Sn(IV) tungstophosphate (Ppy-SWP) nanocomposite cation exchanger is used to study the adsorption of Rhodamine B (RH-B) utilizing batch adsorption by in-situ chemical oxidative polymerization of pyrrole (Ppy) with Sn(IV) tungstophosphate (SWP). FT-IR, XRD, SEM, TEM, and TGA were used to examine the synthesized material’s structural, morphological, and chemical features, revealing the successful Ppy-SWP nanocomposite synthesis. The impact of several parameters, such as pH, adsorbent amount, contact time, and starting dye concentration on RH-B adsorption onto Ppy-SWP, was investigated. The ion exchange capacity (IEC) and maximum level of RH-B dye adsorbed onto Ppy-SWP were reported to be 2.7 meq/g and 209.13 mg/g respectively. Kinetic (pseudo-first order, pseudo-second order, and intraparticle diffusion) and isotherm (Langmuir, Freundlich, Temkin, and Redlich–Peterson) models were used to pick the ideal match for the adsorption data. The Langmuir and Redlich–Peterson isotherm models fit the adsorption data well, while the pseudo-second order model best describes the kinetics data of RH-B adsorption. According to the computed thermodynamic variables standard-free energy, enthalpy, and entropy, the RH-B adsorption onto the Ppy-SWP is a spontaneous, endothermic, and physical sorption process. Even after seven cycles, regeneration experiments revealed an efficiency of greater than 80%.

Synthesis of a maghemite-polypyrrole nanocomposite for the removal of congo red dye from aqueous solutions

A magnetic nanocomposite (MNC) of γ-Fe2O3 nanoparticles (NPs) and polypyrrole (PPY) was synthesized by in-situ chemical oxidative polymerization of pyrrole in presence of FeCl3 as oxidizing agent in order to evaluate its adsorption capacity of Congo red (CR) in aqueous solutions. γ-Fe2O3 NPs were first synthetized by a co-precipitation method with an average particle size of 14 ± 8 nm. In a subsequent step, the MNC was synthesized by the polymerization of pyrrole in an aqueous solution containing the γ-Fe2O3 NPs. The resulting material consisted of maghemite NPs embedded within the polymeric matrix of PPY. The magnetization curves demonstrated the superparamagnetic behavior of the γ-Fe2O3 NPs at room temperature (Ms = 60 emu/g), while the magnetization value of the γ-Fe2O3/PPY MNC decreased up to 14 emu/g. We evaluated the CR adsorption removal of the MNC as a function of the pH, interaction time and the initial dye concentration. The maximum adsorption capacity (qe) achieved was 269.5 mg/g at pH 7.0 and 60 min of interaction time. The present work shows the production of an effective and economic magnetic adsorbent for the removal of dyes from aqueous solutions.

In-situ synthesis of polypyrrole/silver for fabricating alginate fabrics with high conductivity, UV resistance and hydrophobicity

In this research, the polypyrrole/silver (PPy/Ag) composite was first in-situ prepared on alginate fabrics by chemical oxidative polymerization of pyrrole (Py) monomer using silver nitrate as oxidant and sodium dodecyl sulfate (SDS) as the dopant. The effects of mole ratio of Py to silver nitrate, reaction time and dopant concentration on the preparation of PPy/Ag composite were optimized. It was found the optimal molar ratio of Py to silver nitrate was 1:1.5 with 0.02 M SDS under the reaction time of 10 h. Then, the microstructure and properties of resultant PPy/Ag composite were analyzed by scanning electron microscope (SEM), Fourier infrared spectrometer (FT-IR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and the thermogravimetry analysis (TGA), respectively. Finally, the influences of PPy/Ag coating on the performance of alginate fabrics including electrical conductivity, hydrophilicity, antistatic property and anti-ultraviolet capability were determined. It was found that the electrical conductivity of alginate fabric could be intensively increased after PPy/Ag coating. Meantime, the anti-ultraviolet capability and hydrophobicity could be largely improved by PPy/Ag coating especially under high Py dosage. This paper introduced a simple method for preparing PPy/Ag composite direct on alginate fabric to make it a good functional substrate which could be applied in many fields.

Synthesis of polypyrrole – chitosan magnetic nanocomposite for the removal of carbamazepine from wastewater: Adsorption isotherm and kinetic study

A polypyrrole–chitosan–Fe3O4 magnetic nanocomposite (PPy–CS–Fe3O4 MNC) was prepared by in situ coprecipitation of iron salts in the presence of chitosan followed by chemical oxidative polymerization of pyrrole on the magnetic chitosan. Afterward, the nanocomposite was applied as a magnetic nanosorbent for the removal of carbamazepine (CBZ) from the wastewater samples. The prepared adsorbent was characterized by various modern surface and microstructure analyzing methods. Several operating parameters affecting the removal efficiency of the CBZ including sample pH, amount of sorbent, initial concentration and adsorption time were investigated and adjusted. However, under the optimal conditions, the PPy–CS–Fe3O4 MNCs showed prominent removal performance compared to the bare Fe3O4 magnetic nanoparticles. According to the results, the PPy–CS–Fe3O4 MNCs could eliminate the CBZ from water medium with an efficiency of 94.5% in the 25 min. In contrast, it took about an hour to remove 65% of the CBZ using bare Fe3O4 magnetic nanoparticles. The experimental results revealed that the CBZ sorption on the PPy–CS–Fe3O4 MNCs was fitted well with the pseudo-second-order kinetic model (R2 = 0.9901). Moreover, the adsorption model was in accordance with the Langmuir isotherm with the adsorption capacity of 121.95 mg g−1. It was found that PPy–CS–Fe3O4 MNCs could be frequently applied for CBZ removal up to five times without noticeable decrease in its adsorption efficiency. The adsorption results established the high potential of synthesized MNCs as a robust and promising adsorbent for water treatment.

High-yield preparation of molybdenum disulfide/polypyrrole hybrid nanomaterial with non-covalent interaction and its supercapacitor application

• High-yield of molybdenum disulfide (MoS 2 ) nanosheets could be prepared by simple grinding and sonochemical exfoliation. • Polypyrrole/MoS 2 (MPY) hybrid was synthesized via a chemical oxidative polymerization according to pyrrole content. • Non-covalent Mo–N bonding of MPY made it possible to have lowered interfacial resistance and improved surface conductivity. • MPY electrodes showed enhanced specific capacitance and electrochemical stability for pseudocapacitive behavior. Molybdenum disulfide (MoS 2 ) incorporated with a conducting polymer can be a promising nanomaterial for use as low-cost electrodes in supercapacitors. MoS 2 nanosheets are generally prepared by the high-pressure hydrothermal method, which has a few drawbacks such as low exfoliation yield, safety issues, and long-time processing. Herein, we report a simple and effective method for the high-yield (~72.5%) preparation of a MoS 2 /polypyrrole (MPY) hybrid nanomaterial via sonochemical exfoliation of ground bulk MoS 2 in a polar aprotic solvent and subsequent chemical oxidative polymerization of pyrrole (PY) onto the MoS 2 nanosheets. The strong non-covalent Mo–N bonding lowers the interfacial resistance, and the morphology of polypyrrole (PPY) can be easily controlled by varying the PY content. The MPY hybrid nanomaterial exhibited a maximum surface conductivity of 991 S sq., which is very high compared to that of pristine MoS 2 nanosheet (~3.6 × 10 –7 S sq.). When used in supercapacitors, the specific capacitance of the hybrid nanomaterial is 312 F g –1 . Thus, improved capacitance retention with increase in the scan rate and enhanced diffusion process during electrochemical reactions result in good supercapacitor performance, which is important for the mass production of energy-storage devices.

Continuous and controllable synthesis of MnO2/PPy composites with core–shell structures for supercapacitors

A slug-based microreactor system was constructed to integrate the redox reaction between KMnO4 and MnSO4 with the chemical oxidative polymerization of pyrrole for the preparation of MnO2/PPy composite with a typical core–shell structure. MnO2 was formed as the core while PPy acted as the shell. The size distribution variation of MnO2 particles was elaborated by the crystallization theory and the comparison between the micromixing time and the nucleation induction time. It was found that the morphology of the MnO2/PPy composite was significantly affected by the molar ratio among KMnO4, MnSO4 and pyrrole and the residence time due to the competition between the pyrrole polymerization and the MnO2 crystallization. A probable mechanism for the formation of the PPy/MnO2 composite was proposed. The electrochemical performance of the MnO2/PPy composite with core–shell was better than that of MnO2. The enhanced performance demonstrated the synergistic effect between MnO2 and PPy for the fabrication of the core–shell structure. This work developed the design of particles with core–shell structures from the droplet-based microreactor to the slug-based microreactor with a relatively higher flux. The size of the prepared material decreased from microscale in the droplet-based microreactor to nanoscale in this slug-based microreactor. Such a novel strategy can be applied for efficiently preparing functional materials with controllable structures and properties.

Cable-like β-AgVO3@PPy Nanowires as Novel Anode Materials for Lithium-Ion Batteries

β-AgVO3 has been considered as an ideal cathode material for lithium primary batteries for medical devices. Considering its tunnel structure and multiple reductions of both silver and vanadium, β-AgVO3 may be a promising anode material for lithium-ion batteries (LIBs). Herein, we synthesize cable-like β-AgVO3@polypyrrole (PPy) nanowires by chemical oxidative polymerization of pyrrole on the surface of the microwave-hydrothermally (M-H) synthesized β-AgVO3 nanowires. The electrochemical behaviors and the discharge/charge mechanism of the as-prepared cable-like β-AgVO3@PPy nanowires as the anode for LIBs are studied for the first time. The cable-like β-AgVO3@PPy nanowire electrode exhibits higher discharge capacity, better cycle stability, and lower apparent activation energy. The present study indicates that the PPy coating is beneficial to improve the electronic/ion conductivity, reduce charge transfer resistance, and maintain structural stability during the cycling process.

Plasma-Assisted Grafting of PPY on Polyester Fabric as Gas Transducer

In this study, we have grafted polypyrrole (PPY) on polyester fabrics by chemical oxidative polymerization of pyrrole using ferric chloride (FeCl3) as oxidant and sodium dodecyl benzene sulfonate as a dopant. Polyester fabric treated with radio frequency oxygen plasma prior to grafting of PPY showed better deposition and adhesion. Characterization of both untreated and plasma-treated conducting fabrics was done using ATR-FTIR, XPS, SEM, contact angle, and sheet resistance measurement. It was found that higher amount of PPY with uniform grafting, better conductivity, and strong interfacial bonding of PPY on the surface of polyester fabric was accomplished by oxygen plasma treatment. Such oxygen plasma pretreated PPY grafted polyester fabrics were then tested for detection of ammonia gas.

Pseudocapacitive Behaviors of Polypyrrole Grafted Activated Carbon and MnO2 Electrodes to Enable Fast and Efficient Membrane-Free Capacitive Deionization.

Capacitive deionization (CDI) has emerged as a promising technique for brackish water desalination. Here, composites of polypyrrole grafted activated carbon (Ppy/AC) were prepared via in situ chemical oxidative polymerization of pyrrole on AC particles. The Ppy/AC cathode was then coupled with a MnO2 anode for desalination in a membrane-free CDI cell. Both the Ppy/AC and MnO2 electrodes exhibited pseudocapacitive behaviors, which can selectively and reversibly intercalate Cl- (Ppy/AC) and Na+ (MnO2) ions. Compared to AC electrodes, the specific capacitances of Ppy/AC electrodes increased concurrently with the pyrrole ratios from 0 to 10%, while the charge transfer and ionic diffusion resistances decreased. As a result, the 10%Ppy/AC-MnO2 cell showed a maximum salt removal capacity of 52.93 mg g-1 (total mass of active materials) and 34.15 mg g-1 (total mass of electrodes), which was higher than those of conventional, membrane, and hybrid CDI cells. More notably, the salt removal rate of the 10%Ppy/AC-MnO2 cell (max 0.46 mg g-1 s-1 to the total mass of active materials and 0.30 mg g-1 s-1 to the total mass of electrodes) was nearly 1 order of magnitude higher than those in most previous CDI studies, and this fast and efficient desalination performance was stabilized over 50 cycles.

Simple Label-Free DNA Sensor Based on CeO2 Nanorods Decorated with Ppy Nanoparticles

A facile label-free DNA sensor based on cerium oxide nanorods decorated with polypyrrole nanoparticles (CeO2-NRs/Ppy-NPs) matrix has been developed for detection of Salmonella. The sensor was fabricated by hydrothermal synthesis of CeO2-NRs on the microelectrode surface followed by in situ chemical oxidative polymerization of pyrrole on the CeO2-NRs to prepare a CeO2-NR/Ppy-NPs electrode. Single-stranded DNA (ssDNA) sequences were immobilized onto the modified microelectrode by covalent attachment. The properties of the material were explored by field-emission scanning electron microscopy, x-ray diffraction analysis, and Fourier-transform infrared spectroscopy techniques. The response of the DNA biosensor was investigated by electrochemical impedance spectroscopy with [Fe(CN)6]3−/4− as redox probe. The results showed that the response of the DNA biosensor exhibited good linearity within the range of 1.0 × 10−9 mol L−1 to 1.0 × 10−6 mol L−1 with sensitivity of 14.7 × 106 Ω/mol L−1 cm−1. The limit of detection and limit of quantification of the DNA biosensor were low, with values of 2.86.10−7 mol L−1 and 9.56.10−7 mol L−1, respectively.

Titanium dioxide and polypyrrole molecularly imprinted polymer nanocomposites based electrochemical sensor for highly selective detection of p-nonylphenol

We developed a new electrochemical sensor based on TiO2 and polypyrrole (PPy) molecularly imprinted polymer (MIP) nanocomposites for the high selective detection of p-nonylphenol in food samples, which is considered as a kind of endocrine disrupting chemical and harmful to human health. With p-nonylphenol as template molecules, the molecularly imprinted polymer was synthesized by the chemical oxidative polymerization of pyrrole and deposited on the surface of TiO2 nanoparticles to form partially encapsulated PPy@TiO2 nanocomposites, denoted as NP-PPy@TiO2 MIP. p-Nonylphenol was bound in the PPy matrix through hydrogen bond and π-π interaction between p-nonylphenol and PPy skeleton. NP-PPy@TiO2 MIP nanocomposites were modified onto glassy carbon electrode (GCE) and p-nonylphenol molecules were excluded from PPy layers by potentiostatic sweeping at the potential of 1.3 V. The as-prepared electrochemical sensor obtained a large amount of micro cavities in PPy layer which could specially recognize and combine target molecules p-nonylphenol. After special adsorption of p-nonylphenol from samples, p-nonylphenol embedded in the PPy layer exhibited a strong differential pulse voltammetry (DPV) response at 0.56 V, which can be used for the detection of p-nonylphenol with a linearly proportional concentration range of 1.0 × 10−8 to 8 × 10−5 mol/L and a detection limit of 3.91 × 10−9 mol/L. The good stability, reproducibility and specificity of the resulting MIP electrochemical sensor are demonstrated. It might open a new window for investigation of selectively electrochemical sensing of small organic molecules from their analogues with the molecular imprinting technique.

Electrochemical behavior of composite electrode based on sulphonated polymeric surfactant (SPEEK/PSS) incorporated polypyrrole for supercapacitor

Sulfonated polymeric surfactants integrated polypyrrole composites have been prepared and exploited as electrode material for supercapacitor application where sulfonated poly (ether ether ketone) SPEEK and poly (styrene sulfonate) PSS have been used as surfactant as well as dopant in polypyrrole (PPy). These composites are conveniently prepared via in-situ chemical oxidation polymerization of pyrrole using FeCl3 as oxidant at varying weight ratio of SPEEK/PSS and investigated through Fourier transforms infrared spectroscopy, Thermal gravimetric analysis/Derivative thermal gravimetric, Field emission scanning electron microscopy, and electrochemical performance. Field emission scanning electron micrographs divulge granular morphology of composite with spongy and baggy structure. Electrochemical performance of all the composites has been investigated through cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements. Results reveal that electrochemical properties of composites significantly depend upon different feeding ratio of SPEEK or PSS due to the availability of sulfonating groups. After comparative study, high specific capacitance 330F/g of SP4 (PPy:SPEEK (w/w) 60:40) at scan rate of 2mV/s, that also correlates well with the GCD findings. High energy density obtained as 23.8Wh/kg of SP4 composite at power density of 1000W/kg demonstrates as new promising electrode material for supercapacitors.

Synergistic effect of polypyrrole/BST/RGO/Fe3O4 composite for enhanced microwave absorption and EMI shielding in X-Band

Present study focus on the designing of high performance microwave absorbing material against electromagnetic pollution. Herein we synthesize conducting polymer based composite encapsulated with Barium strontium titanate (BST), reduced graphene oxide (RGO), and Fe3O4 nanoparticles via chemical oxidative polymerization of pyrrole. The synthesized composite materials were thoroughly characterized using SEM, FTIR, XRD, TGA, and VSM techniques. The presence of filler materials in conducting polymer matrix leads to absorption dominated shielding effectiveness value of 48 dB in the frequency range of 8.2–12.4 GHz (X-band). Moreover, presence of dielectric and magnetic fillers increases the thermal and chemical stability of the composite material. The obtained shielding effectiveness value is above the recommended limit (30–40 dB) required for the commercial applications, therefore these composite material could be used as effective shield against EM pollution.

Multifunctional polypyrrole@maghemite@silver composites: synthesis, physico-chemical characterization and antibacterial properties

Maghemite (γ-Fe2O3) nanoparticles were synthesized by coprecipitation of ferrous and ferric salts with ammonia and oxidation with sodium hypochlorite. Polypyrrole (PPy) was obtained, by the chemical oxidative polymerization of pyrrole in an aqueous solution in the presence of iron oxide nanoparticles. The morphology of PPy was turned from globular to nanofibers by addition of dyes. The resulting PPy@γ-Fe2O3 hybrid composites were characterized by transmission electron microscopy, magnetic and electrical conductivity measurements and energy dispersive X-ray spectroscopy. Both the electrical conductivity and magnetic properties of the PPy@γ-Fe2O3 nanocomposites were controlled by the maghemite content due to the insulating properties of magnetic iron oxide nanoparticles added to the conducting polymer. Antibacterial activity of all materials was defined by determination of minimal inhibitory concentration. Antibacterial properties of native materials were improved by the reduction of silver ions from an aqueous solution to obtain PPy@γ-Fe2O3@silver composites. Due to the antibacterial properties of these composites, especially of those with silver particles, they can be considered for the applications where bacterial contamination can deteriorate the functionality of material.

Synthesis and Characterization of Polypyrrole/ Praseodymium Calcium Manganite Oxide Nanocomposites

Polypyrrole (PPy) has immensely attracted research workers because of its stable thermal and chemical properties, utilization as batteries, sensors, electronic conductors, optical switching devices, etc. The properties of PPy as conducting polymers may be improved by developing innovative methods. The nanoparticles may be incorporated inside the PPy which would increase the charge storage capacity comparatively. This paper reports the synthesis of organic-inorganic hybrid Polypyrrole (PPy) - Pr0.75Ca0.25MnO3 (PCMO) nanocomposites with various compositions viz., 10, 20, 30, 40 and 50 wt.% via chemical oxidative polymerization of pyrrole in presence of PCMO nanoparticles using ammonium persulphate as oxidant. All the samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM). Frequency dependence of real dielectric constant (εl) and imaginary dielectric constant (εll) were studied using impedance analyzer. It was observed that dielectric constant εl decreased abruptly at lower frequencies and showed almost frequency independent behavior at higher frequency region. The imaginary dielectric constant (εll) was found to be less at higher frequencies than lower frequency region. The possible reasons for the variation in εl and εll with frequency will be discussed in this paper.

Composite nanofibers by coating polypyrrole on the surface of polyaniline nanofibers formed in presence of phenylenediamine as electrode materials in neutral electrolyte

Polyaniline/Polypyrrole (PANi/PPy) composite nanofibers with core–shell structures were prepared by covering PPy thin layers on the surface of PANi nanofibers as high–performance electrode materials for supercapacitors in neutral aqueous electrolyte. Core part of PANi was firstly synthesized through chemical oxidative polymerization of aniline monomers in the presence of phenylenediamine (PDA) isomers including o–phenylenediamine (o–PDA), m–phenylenediamine (m–PDA) and p–phenylenediamine (p–PDA) without the assistance of any templates or usage of organic solvents, and then the shell part of PPy was fabricated by in–site chemical oxidative polymerization of pyrrole with the above–mentioned PANi as a seed. PANis and corresponding composite were investigated by field–emission scanning electron microscopy, ultraviolet–visible spectroscopy, Fourier transform infrared and Raman spectrometry, and wide angle X–ray diffractometer. Furthermore, electrochemical behaviors of PANis in H2SO4 and Na2SO4 electrolyte as well as corresponding composites in Na2SO4 electrolyte were tested by cyclic voltammetry, galvanostatic charge–discharge techniques and electrochemical impedance spectroscopy. It is found that compared with pure PANi prepared without PDA isomers, the incorporation of o–PDA and p–PDA is helpful to improve the electrochemical property of PANi nanofibers. Especially for o–PDA, the resulting PANi nanofibers exhibited the largest specific capacitance of 1115.7Fg−1 at the scan rate of 5mVs−1, and 345.3Fg−1 at the specific current of 0.5Ag−1 in 1.0M H2SO4 electrolyte. However, in 0.5M Na2SO4 electrolyte, its specific capacitance decreased to 254.5 and 210.4Fg−1, whereas 834.6 and 652.5Fg−1 for PANi/PPy composites at the scan rate of 5mVs−1 and at the specific current of 0.5Ag−1, respectively. Moreover, a great improvement on cycling stability for the composites could be achieved, benefiting from the unique core–shell nanostructure and strong synergy effect between PANi and PPy.

DC electrical conductivity and rate of ammonia vapour-sensing performance of synthetic polypyrrole\u2013zirconium(IV) phosphate cation exchange nanocomposite

Electrically conductive polypyrrole–zirconium(IV) phosphate (PPy–ZrP) cation exchange nanocomposites have been synthesized for the first time by in situ chemical oxidative polymerization of pyrrole in the presence of zirconium(IV) phosphate (ZrP). Fourier Transform Infra-red spectroscopy (FTIR), field emission scanning electron microscopy, transmission electron microscopy, X–ray diffraction, thermogravimetric analysis, differential thermal analysis, derivative thermogravimetry and elemental analysis were used to characterize PPy–ZrP cation exchange nanocomposite. The composite showed good ion-exchange capacity (1.60 meq g−1), DC electrical conductivity (0.33 S cm−1) and isothermal stability in terms of DC electrical conductivity retention under ambient condition up to 100 °C. PPy–ZrP cation exchangenanocomposite-based sensor was fabricated for the detection of ammonia vapours of aqueous ammonia. The resistivity of the nanocomposites increases on exposure to high-concentration ammonia vapours at room temperature (25 °C). The rate of reaction for ammonia vapour-sensing on PPy–ZrP was observed as second order.