Study of DC conductivity and relative magnetic permeability of nanoparticle NiZnFe2O4/PPy composites

The DC conductivity and the relative magnetic permeability have been measured as functions of temperature for five powder samples of nanoparticle ferrites (Ni_xZn_1−xFe₂O₄; x=0, 0.25, 0.5, 0.75 and 1), a pure polypyrrole (PPy) powder sample and many composite samples prepared by mixing different ratios of the ferrites to PPy. By comparing the results it is found that there is an obvious increase in DC conductivity of the ferrite/PPy composite samples compared to the corresponding pure ferrite samples, whereas compared to the pure PPy sample there is a decrease in DC conductivity. On the contrary, the magnetic permeability of the composites is higher than that of the pure PPy sample and lower than that of the pure ferrite samples as was expected.     

Combination of Fe-Mn based Li-rich cathode materials and conducting-polymer polypyrrole nanowires with high rate capability

The polypyrrole (PPy) nanowires are conducting 1D materials, which can significantly improve the electrical conductivity of the composites. A novel Li_1.26Fe_0.22Mn_0.52O₂ (LFMO) @ PPy nanowire composites were synthesized by simply ultrasonic dispersing LFMO and PPy nanowires in aqueous ethanol. The structure and morphology of pristine LFMO and LFMO@PPy are investigated by XRD, SEM, and TEM. The elemental mapping and FTIR results demonstrate the conductive network of PPy nanowires exists in the composites and the LFMO particles uniformly distribute on the PPy nanowires. LFMO combined with PPy nanowires exhibits better rate capability, higher capacity, coulombic efficiency, and cycleability than the pristine. The rate performance of composites with 10 wt% PPy nanowires shows the discharge capacities of 132.2 mAh/g and 98 mAh/g at 1C and 3C rate after 50 cycles, respectively. Electrochemical impedance spectroscopy test suggests that the conductive PPy nanowires can significantly decrease the charge-transfer resistance of LFMO. The composite with 10 wt% PPy nanowires shows a discharge capacity retention of 71% after 50 cycles at 1C, while the pristine sample only has 50% capacity retention.     

EPR and XPS measurements of polymeric catalysts doped with hereopolyacids in oxygen adsorption studies

The goal of our studies was to determine the nature of interactions between catalytic active samples, such as polypyrrole (PPy) doped with: chloride anions, heteropolyacids such as H₅PMo₁₀V₂O₄₀, or H₄SiW₁₂O₄₀, and oxygen particles. In order to reveal the mechanism of the linkage between the catalysts and oxygen we provided the electron paramagnetic resonance (EPR) measurements of synthesized samples in O₂ and N₂ flow. Moreover, the X-ray photoelectron spectroscopy (XPS) measurements were performed to show the properties of doped heteropolyacids and the state of nitrogen in polypyrrole matrix. The results of EPR studies of PPy(Cl), PPy(H₄SiW₁₂O₄₀), PPy(H₅PMo₁₀V₂O₄₀) samples, show that the polypyrrole doped with chloride anions interacts much easier with oxygen than polypyrrole doped with heteropolyacids (in the above given order, of preference with the most active polypyrrole system first). It correlates with XPS results, which show that a molybdenium-vanadium anion is more reduced than a silicon-tungsten one. The redox reactions of heteropolyacids involve the oxidation-reduction of the conjugated polymer chain, leaving no or little place for interactions with oxygen. Polypyrrole doped with H₄SiW₁₂O₄₀ shows some oxygen sensitivity as observed in the EPR studies, as opposed to polypyrrole doped with H₅PMo₁₀V₂O₄₀, which is in line with the XPS results.     

Study of alternating current conduction mechanism in polypyrrole-magnesium ferrite hybrid nanocomposite through correlated barrier hopping model

In the present work, both polypyrrole (PPy) and optimized polypyrrole–magnesium ferrite (PPy-MgFe₂O₄) hybrid nanocomposite were synthesized separately by simple oxidative chemical polymerization method and then structurally characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The FTIR spectrum of the composite showed the presence of characteristic absorption bands of both PPy and MgFe₂O₄ in the composite confirming interfacial interaction of PPy with MgFe₂O₄. That this interaction is not affected by crystalline behaviour of predominant MgFe₂O₄ particles but that MgFe₂O₄ has embedded in PPy matrix was confirmed by XRD studies. Agglomerated granular spherical morphology of the composite was confirmed by SEM studies. Decrease in AC conductivity of the composite as compared to PPy due to the formation of interfacial heterojunction barrier between p-type PPy and n-type MgFe₂O₄ was confirmed experimentally and well supported theoretically by calculating binding energy, hopping distance and density of states at Fermi level of PPy and the composite as per CBH model.     

Improved electrical,magnetic and dielectric properties of polypyrol (PPy) substituted spinel ferrite composites

CoTb_0.03Fe_1.97O₄ ferrite and poypyrrole (PPy) polymer nano composites were prepared by mixing the nano crystalline ferrite with poypyrrole (PPy) by following the solid state reaction synthesis route. The XRD patterns of CoTb_0.03Fe_1.97O₄ spinel ferrite powders and polymer (PPy) exhibited single phase spinel structure. The amorphous nature of PPy was evidenced by the broad peaks of XRD patterns. The surface morphology unfolded heterogeneous distribution in composites and ferrite. The grains in ferrite were spherical in shape with clear boundaries. The morphology was appreciably altered by the inclusion of ferrite contents. The higher activation energy and resistivity aroused due to blocking of conduction mechanism owing to nanoparticles embedded in the PPy matrix. A downfall in the dielectric loss of the composites is observed as the frequency of the applied field is increased. The incorporation of ferrite contents optimized the magnetic parameters of the composites. The enhanced coercivity (Hc) of these nanocomposites might be beneficial for memory devices.     

Preparation and electrochemistry of one-dimensional nanostructured MnO2/PPy composite for electrochemical capacitor

One-dimensional nanostructured manganese dioxide/polypyrrole (MnO₂/PPy) composite was prepared by in situ chemical oxidation polymerization of pyrrole in the host of inorganic matrix of MnO₂, using complex of methyl orange (MO)/FeCl₃ as a reactive self-degraded soft-template. The morphology and structure of the composite were characterized by infrared spectroscopy (IR) X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the MnO₂/PPy composite consists of α-MnO₂ and PPy with nanotube-like structure. Electrochemical properties of the composite demonstrated the material showed good electrochemical reversibility after 500 charge-discharge cycles in the potential range of −0.4 to 0.6 V, the tube-like nanocomposite has the potential application in electrochemical capacitor.     

Synthesis and characterization of polypyrrole/Sn-doped TiO2 nanocomposites (NCs) as a protective pigment

We have chemically polymerized pyrrole in the presence of Sn-doped TiO₂ nanoparticles (NPs) and TiO₂ (NPs) which act as a protective pigment. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) results show a core-shell structure of pigments in which TiO₂ and Sn-doped TiO₂ NPs have a nucleus effect and caused a homogenous PPy core-shell type morphology leading to coverage of the TiO₂ and Sn-doped TiO₂ NPs by PPy deposit. The XRD results indicate that the crystalline size of polypyrrole/TiO₂ NCs and polypyrrole/Sn-doped TiO₂ NCs were approximately 93.46 ± 0.06 and 23.36 ± 0.06 nm respectively. The electrochemical impedance spectroscopy (EIS) results show that the performance of polypyrrole/Sn-doped TiO₂ NCs is better than polypyrrole/TiO₂ NCs. The results indicate that increasing the area of synthesized polypyrrole in the presence of Sn-doped TiO₂ NPs can increase its ability to interact with the ions liberated during the corrosion reaction of steel in the presence of NaCl. The UV-vis results show that the band gap of TiO₂ NPs increases with doped of Sn in lattice of TiO₂. The increase of the band gap of TiO₂ with doping of Sn can decrease the charge transfer through the coating.     

Synthesis and characterization of hybrid nanocomposites of polypyrrole filled with iron oxide nanoparticles

Hybrid polypyrrole (PPy)/α-Fe₂O₃ nanocomposite films were fabricated by spin coating on a glass substrate. X-Ray diffraction analysis revealed the crystalline structure of α-Fe₂O₃ nanostructures and the nanocomposites. The broad PPy peak weakened in intensity as the α-Fe₂O₃ content increased in PPy/α-Fe₂O₃ nanocomposites. Characteristic Fourier-transform IR peaks for pure PPy shifted to higher wavenumbers on addition of α-Fe₂O₃ to PPy/α-Fe₂O₃ nanocomposites. This can be attributed to better conjugation and interactions between PPy and α-Fe₂O₃ nanoparticles. Field-emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy images of the nanocomposites reveal a uniform distribution of α-Fe₂O₃ nanoparticles in the PPy matrix. UV-vis absorption spectroscopy revealed a blue shift from λ_max= 441 nm for PPy to λ_max= 392 nm for PPy/α-Fe₂O₃, reflecting strong interactions between PPy and α-Fe₂O₃ nanoparticles. The room-temperature dc electrical conductivity increased from 4.33×10⁻⁹ to 1.81×10⁻⁸ S/cm as the α-Fe₂O₃ nanoparticle content increased from 10 to 50 wt.% in PPy/α-Fe₂O₃ nanocomposites.     

Preparation of pyrrole with iron oxide precipitated on the surface of graphite nanosheet

Fe₃O₄/NanoG was firstly prepared by precipitation reaction of iron oxide (Fe₃O₄) on the surface of graphite nanosheet (NanoG). Then composites PPy/NanoG, PPy/Fe₃O₄ and PPy/Fe₃O₄/NanoG were prepared by in-situ polymerization of the monomer pyrrole polymerized on the surface of NanoG, Fe₃O₄ and Fe₃O₄/NanoG. The structures of Fe₃O₄/NanoG, PPy, PPy/NanoG, PPy/Fe₃O₄ and PPy/Fe₃O₄/NanoG were characterized by scanning electron microscopy, energy dispersive spectroscopy, fourier transmission infrared spectroscopy and X-ray diffraction . Results show that NanoG and Fe₃O₄/NanoG are encapsulated by PPy for the layered structure and their high aspect ratio (300–500). From the thermogravimetric analysis it can be seen that the introductions of NanoG, Fe₃O₄ and Fe₃O₄/NanoG into PPy based composites lead them to exhibit better thermal stabilities than pure PPy. The measurements of electromagnetic parameters show that the reflection loss of PPy/Fe₃O₄/NanoG is below −15 dB at the X band (8.2–12.4 GHz) and the minimum loss value is −18.30 dB at 9.84 GHz, while the reflection loss of PPy/Fe₃O₄ is below −10 dB at 8.2–12.4 GHz and the minimum loss value is −14.02 dB at 10.26 GHz. The reflection loss of PPy/NanoG is below −10 dB at 8.2–12.4 GHz and the minimum loss value is −13.44 dB at 10.28 GHz. The microwave absorbing properties of PPy/Fe₃O₄/NanoG, PPy/Fe₃O₄ and PPy/NanoG are superior to that of PPy.     

One‐Pot Synthesis of Algae‐Like MoS2/PPy Nanocomposite: A Synergistic Catalyst with Superior Peroxidase‐Like Catalytic Activity for H2O2 Detection

A facile one‐pot synthetic route is reported to prepare algae‐like molybdenum disulfide/polypyrrole (MoS₂/PPy) nanocomposite through a redox reaction between ammonium tetrathiomolybdate and pyrrole monomer under a hydrothermal condition without any other templates. The as‐prepared unique algae‐like MoS₂/PPy nanocomposites are composed of few layer MoS₂ nanosheets, which are covered with PPy. Structural and morphological characterizations of this unique nanocomposite are investigated by Fourier‐transform infrared spectra, Raman spectra, X‐ray diffraction pattern, X‐ray photoelectron spectra, energy‐dispersive X‐ray spectroscopy, and transmission electron microscopy. The as‐prepared MoS₂/PPy nanocomposites exhibit an excellent peroxidase‐like catalytic activity toward the oxidation of 3,3,5,5‐tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂) in acetate buffer solution (pH 4.0), which provides a facile strategy for the colorimetric detection of H₂O₂ with a high sensitivity.     

Morphology,conductivity, and mechanical properties of polypyrrole-containing composites

An electrical-conducting polypropylene/polypyrrole (PP/PPy) composite was prepared by the chemically oxidative modification reaction of pyrrole on the surface of PP particles in suspension. Another type of PP/PPy composite was prepared by mixing the coated PP particles with noncoated PP particles at room temperature. The composites were processed by compression molding or by injection molding. The injection-molded composites exhibited better mechanical properties compared to compression-molded samples, while these composites showed better antistatic behavior and electrical conductivity. The differences in the behavior of the two types of composites were caused by the different structure of the PPy phase, which was studied by hot-stage optical microscopy and X-ray photoelectron spectroscopy (XPS).     

Preparation of Si-PPy-Ag composites and their electrochemical performance as anode for lithium-ion batteries

The nanosilicon connected by polypyrrole (PPy) and silver (Ag) particles was simply synthesized by a chemical polymerization process in order to prepare Si-based anodes for Li-ion batteries. The phase structure, surface morphology, and electrochemical properties of the as-synthesized powders were analyzed by X-ray diffraction, FT-IR, scanning electron microscopy, and galvanostatic charge/discharge measurements. The cycle stability of the Si-PPy-Ag composites was greatly enhanced compared with the pure nanosilicon. A high capacity of more than 823 mA h g^?1 was maintained after 100 cycles. The improved electrochemical characteristics are attributed to the volume buffering effect as well as effective electronic conductivity of the polypyrrole and silver in the composite electrode.     

The photovoltaic effect of the p–n heterojunction organic photovoltaic device using a nano template method

Characteristics of ITO/polypyrrole (PPy) nano fibers/poly(3-hexylthiophene)/Al photovoltaic devices prepared by nano template method were studied. PPy nano fibers on ITO glass were formed through nano pores of polymer membrane template using home made special sample holder by electrochemical polymerization in an electrolyte solution of pyrrole and lithium perchlorate as a dopant in acetonitrile. Ordered structure with enhanced interfacial area formed by nano template method enable to fabricate polymeric photovoltaic device with improved photo-conversion efficiency. This nano fiber structures film possesses increased interfacial area, large charge separation area (photoactive zone) and secured charge transportation route. The effect of altering energy levels of PPy by changing doped state was also studied. Device made with nano fiber structure showed enhanced photovoltaic effect than that of overlayed film device.     

Studies of the activity of catalysts based on heteropolyacids

The catalytic activity of samples such as PPy(H₄SiW₁₂O₄₀), PPy(H₅PMo₁₀V₂O₄₀), PPy(H₂Fe(III)PMo₁₀V₂O₄₀), PPy(H₃Cu(II)PMo₁₀V₂O₄₀) has been examined in two different test reactions. The acid-base and oxidation-reduction properties were studied using the conversion of isopropyl alcohol to propene and acetone. Redox ability of catalysts was examined in the reaction of oxidation of allyl alcohol to glycidol. It was found that the activity of catalysts in the oxidation of allyl alcohol increases as the oxidation properties determined from the conversion of isopropyl alcohol increase. It was also observed that stronger oxidation-reduction properties of the catalyst result in a high rate of the consecutive reaction of glycidol to 3-hydroxypropanone.The phase composition of catalysts was determined by means of X-ray diffraction (XRD).     

Characterization of Cu1.4Mn1.6O4/PPy composite electrodes

In this work, we have studied the multilayered polypyrrole(PPy)/oxide composite electrode on glassy carbon (GC) having the structure GC/PPy/PPy(Cu_1.4Mn_1.6O₄)/PPy using X-ray Photoelectron Spectroscopy and Mn K-edge and Cu K-edge XANES and EXAFS. The mixed oxide particles have been incorporated into the PPy matrix simultaneously to the electropolymerization of Py from a solution containing 0.1 M Py + 0.15 M KCl + Cu_1.4Mn_1.6O₄. The XPS data have shown that, prior to the incorporation of the oxide into the PPy matrix, it contains Cu⁺, Cu²⁺, Mn³⁺ and Mn⁴⁺. The XPS, XANES and EXAFS results have shown that when the oxide is incorporated into the PPy matrix, the Cu⁺ present in the original oxide suffers dismutation to give Cu²⁺ and metallic Cu. The metallic Cu is segregated out of the spinel structure. The Mn K-edge XANES and EXAFS data show that, after the incorporation into the PPy matrix, Mn is present as Mn³⁺ and Mn⁴⁺ occupying octahedral sites in a spinel-related structure while the Cu K-edge XANES and EXAFS data indicate that copper occupies tetrahedral sites predominantly in that structure but having a large degree of disorder in the second and higher coordination shells.     

Preparation of Co3O4 nanoplate/graphene sheet composites and their synergistic electrochemical performance

Co₃O₄ nanoplate/graphene sheet composites were prepared through a two-step synthetic method. The composite material as prepared was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The platelet-like morphology of Co₃O₄ leads to a layer-by-layer-assembled structure of the composites and a good dispersion of Co₃O₄ nanoplates on the surface of graphene sheets. The electrochemical characteristics indicate that the specific capacitance of the composites is 337.8 F?g^?1 in comparison with the specific capacitance of 204.4 F?g^?1 without graphene sheets. Meanwhile, the composites have an excellent rate capability and cycle performance. The results show that the unique microstructure of the composites enhances the electrochemical capacitive performance of Co₃O₄ nanoplates due to the three-dimensional network of graphene sheets for electron transport increasing electric conductivity of the electrode and providing unobstructed pathways for ionic transport during the electrochemical reaction.     

Highly Water‐Dispersible,Highly Conductive,and Biocompatible Polypyrrole‐Coated Silica Particles Stabilized and Doped by Chondroitin Sulfate

Currently available methods to prepare conducting polymers‐coated colloidal substrates for biomedical applications need to be improved because they involve the use of toxic reagents and tend to result in aggregated products with diminished conductivity. The work herein describes for the first time a facile strategy for preparing highly water‐dispersible, highly conductive, and biocompatible polypyrrole‐coated silica core–shell (SiO₂@PPy) particles using only chondroitin sulfate (CS), a biologically derived polymer, as the stabilizer and dopant. The CS preadsorbed onto silica surface serves as a template to control the confined growth of the PPy shell and doping of in situ polymerized PPy shell. The thickness of the PPy shell can be tuned from 8 to 17 nm by varying the CS preadsorbed amount. Increasing the thickness of the adsorbed CS layer can control the deposition of thinner PPy shells on an SiO₂ core surface to provide highly water‐dispersible SiO₂@PPy particles. Moreover, CS‐doped SiO₂@PPy particles exhibit conductivities as high as 5.3 S cm^?1. The conductivity of the particles depends on the PPy mass loading and the doping level of the PPy shell. Furthermore, the SiO₂@PPy particles exhibit good biocompatibility and therefore have potential applications in biomedicine.     

Hollow polypyrrole nanosphere embedded in nitrogen-doped graphene layers to obtain a three-dimensional nanostructure as electrode material for electrochemical supercapacitor

A novel approach was developed to prepare hollow polypyrrole (PPy) nanospheres and nitrogen-doped graphene/hollow PPy nanospheres (NG/H-PPy) composites. In this process, uniform poly (methyl methacrylate-butyl methacrylate-methacrylic acid) (PMMA-PBMA-PMAA) latex microspheres as sacrificial templates were synthesized by using an emulsion polymerization method. Then, hollow PPy nanospheres were obtained on the surface of PMMA-PBMA-PMAA microspheres by in situ chemical oxidative polymerization. Finally, H-PPy was embedded in NG layers successfully through a simple approach. The nanobeads have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, and Fourier transform infrared spectra (FTIR). Different electrochemical methods including cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) have been applied to study the electrochemical properties. The specific capacitance of NG/H-PPy composites based on the three-electrode system is as high as 575 F g^?1 at a current density of 1 A g^?1 and enhanced stability about 90.1 % after 500 cycles, indicating that the composite has an impressive capacitance and excellent cycling performance.     

Synthesis and characterization of silver-polypyrrole film composite

In this work, we report the chemical polymerization of pyrrole to obtain thin film of polypyrrole (PPy) hydrochloride deposited onto the electrode of the quartz crystal microbalance (QCM). The film in the base form was exposed to a solution of AgNO₃. Electroless reduction for silver ions by the PPy film took place and silver particles were adsorbed onto the film surface. The silver particles content at the PPy films were analyzed by QCM and the results showed that the concentrations of silver uptakes increase as the original AgNO₃ solution increases. The morphology of the surface of the PPy film and the silver-PPy film composite were studied by the scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDX). They showed that the obtained silver particles have spherical, cubic and tetrahedral structures. X-ray diffraction (XRD) and Fourier transformed infra-red spectroscopy (FTIR) were used to characterize the structure of the powder composite. This work reveals the capability of PPy film coating on QCM in sensing and removing silver from several environmental samples.     

Preparation/Property Relationships for a Nitrate Amperometric Sensor: Effect of Nanowires Polymerization Parameters

Nitrate amperometric sensors based on polypyrrole (PPy) nanowire modified electrodes were developed by electropolymerization of pyrrole with a template‐free method. Polymerization parameters of PPy nanowires were changed to improve the amperometric response to NO₃ ^?. The experimental results show that the polymerization parameters such as concentration of pyrrole, concentration of electrolyte, acidity of polymerization solution, and the kinds and concentration of dopants have significant effects on the morphologies of the nanowires and the electroreduction current density of NO₃ ^?. The PPy nanowires prepared in a solution containing NO₃ ^? have an obvious “memory effect” for NO₃ ^?. The determination sensitivity and detection limit may be varied with the change of modification parameters. The PPy nanowire modified electrode prepared under a certain polymerization condition has good electrocatalytic effect toward electroreduction of NO₃ ^? and has good linearity between the electroreduction current density and the concentration of NO₃ ^?. The sensitivity and detection limit are 606.54 mA/M cm² and 9.98×10^?6 M, respectively.