Preparation and characterization of polypyrrole/magnetite nanocomposites synthesized by in situ chemical oxidative polymerization

This work describes the preparation and characterization of polypyrrole (PPy)/iron oxide nanocomposites fabricated from monodispersed iron oxide nanoparticles in the crystalline form of magnetite (Fe₃O₄) and PPy by in situ chemical oxidative polymerization. Two spherical nanoparticles of magnetite, such as 4 and 8 nm, served as cores were first dispersed in an aqueous solution with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form micelle/magnetite spherical templates that avoid the aggregation of magnetite nanoparticles during the further preparation of nanocomposites. The PPy/magnetite nanocomposites were then synthesized on the surface of the spherical templates. Structural and morphological analysis showed that the fabricated PPy/magnetite nanocomposites are core (magnetite)‐shell (PPy) structures. Morphology of the PPy/magnetite nanocomposites containing monodispersed 4‐nm magnetite nanoparticles shows a remarkable change from spherical to tube‐like structures as the content of nanoparticles increases from 12 to 24 wt %. Conductivities of these PPy/magnetite nanocomposites show significant enhancements when compared with those of PPy without magnetite nanoparticles, in particular the conductivities of 36 wt % PPy/magnetite nanocomposites with 4‐nm magnetite nanoparticles are about six times in magnitude higher than those of PPy without magnetite nanocomposites. These results suggest that the tube‐like structures of 36 wt % PPy/magnetite nanocomposites may be served as conducting network to enhance the conductivity of nanocomposites. The magnetic properties of 24 and 36 wt % PPy/magnetitenanocomposites show ferromagnetic behavior and supermagnetism, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1291–1300, 2008     

Synthesis,characterization, and properties of monodispersed magnetite coated multi‐walled carbon nanotube/polypyrrole nanocomposites synthesized by in‐situ chemical oxidative polymerization

This study describes the preparation of a nanocomposites fabricated from monodispersed 4‐nm iron oxide (Fe₃O₄) coated on the surface of carboxylic acid containing multi‐walled carbon nanotube (c‐MWCNT) and polypyrrole (PPy) by in situ chemical oxidative polymerization. High‐resolution transmission electron microscopy images and X‐ray diffraction (XRD) data indicate that the resulting Fe₃O₄ nanoparticles synthesized using the thermal decomposition are close to spherical dots with a particle size about 4 ± 0.2 nm. The resulting nanoparticles were further mixed with c‐MWCNT in an aqueous solution containing with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form one‐dimensional Fe₃O₄ coated c‐MWCNT template for further preparation of nanocomposite. Structural and morphological analysis using field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, and XRD showed that the fabricated Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are one‐dimensional core (Fe₃O₄ coated c‐MWCNT)‐shell (PPy) structures. The conductivities of these Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are about four times higher than those of pure PPy matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 727–733, 2008     

Characterization and electrical properties of polypyrrole/multiwalled carbon nanotube composites synthesized by in situ chemical oxidative polymerization

This study describes the preparation of polypyrrole (PPy)/multiwalled carbon nanotube (MWNT) composites by in situ chemical oxidative polymerization. Various ratios of MWNTs, which served as hard templates, were first dispersed in aqueous solutions with the surfactant cetyltrimethylammonium bromide to form micelle/MWNT templates and overcome the difficulty of MWNTs dispersing into insoluble solutions of pyrrole monomer, and PPy was then synthesized via in situ chemical oxidative polymerization on the surface of the templates. Raman spectroscopy, Fourier transform infrared (FTIR), field‐emission scanning electron microscopy (FESEM), and high‐resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the fabricated composites. Structural analysis using FESEM and HRTEM showed that the PPy/MWNT composites were core (MWNT)–shell (PPy) tubular structures. Raman and FTIR spectra of the composites were almost identical to those of PPy, supporting the idea that MWNTs served as the core in the formation of a coaxial nanostructure for the composites. The conductivities of these PPy/MWNT composites were about 150% higher than those of PPy without MWNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1413–1418, 2006     

Novel electromagnetic functionalized γ‐Fe2O3/polypyrrole composite nanostructures with high conductivity

In general, the conductivity of polypyrrole (PPy) is reduced by addition of magnetic nanoparticles as the additives owing to insulating effect of magnetic nanoparticles. In this article, novel electromagnetic functionalized PPy composite nanostructures were prepared by a template‐free method associated with γ‐Fe₂O₃ nano‐needles as the hard templates in the presence of p‐toluene‐sulfonic acid (p‐TSA) and FeCl₃·6H₂O as the dopant and oxidant, respectively. It was found that the molar ratio of γ‐Fe₂O₃ to pyrrole monomer represented by [γ‐Fe₂O₃]/[Py] ratio strongly affected the morphology and the conductivity of the γ‐Fe₂O₃/PPy composite nanostructures. A growth mechanism for the composite nanostructures was proposed based on the variance of the morphology with the [γ‐Fe₂O₃]/[Py] ratio. Compared with previously reported γ‐Fe₂O₃/PPy composites, the as‐prepared novel composite nanostructures showed much higher conductivity (up to ～50 times higher). Moreover, the synthesized γ‐Fe₂O₃/PPy composite nanostructures displayed ferromagnetic behavior with a high coercive force. Explanations for these interesting observations were made in terms of the magnetic interaction between ferromagnetic γ‐Fe₂O₃ nano‐needles and spin‐polaron of PPy nanotubes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4446–4453, 2009     

Facile one‐step synthesis of electromagnetic functionalized polypyrrole/Fe3O4 nanotubes via a self‐assembly process

This article reports a simple self‐assembly process for facile one‐step synthesis of novel electromagnetic functionalized polypyrrole (PPy)/Fe₃O₄ composite nanotubes using p‐toluenesulfonic acid (p‐TSA) as the dopant and FeCl₃ as the oxidant. The key trick of the present method is to use FeCl₃ as the oxidant for both PPy and Fe₃O₄ in the same time to synthesize PPy/Fe₃O₄ composite nanotubes in one‐step. This facile one‐step method is much simpler than the conventional approach using the Fe₃O₄ nanoparticles as the additives. Compared to the similar composites synthesized using the conventional method, the as‐prepared PPy‐p‐TSA/Fe₃O₄ composite nanotubes using the facile one‐step self‐assembly process show much higher room‐temperature conductivity. Moreover, the composite nanotubes display interesting ferromagnetic behavior. The electrical properties of the PPy‐p‐TSA/Fe₃O₄ composite nanotubes are dominated by the amount of FeCl₃ while their magnetic properties are controlled by the amount of FeCl₂. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 320–326, 2010     

Decoration of Fe3O4 nanoparticles on the surface of poly(acrylic acid) functionalized multi‐walled carbon nanotubes by covalent bonding

Fe₃O₄ nanoparticles were indirectly implanted onto functionalized multi‐walled carbon nanotubes (MWCNTs) leading to a nanocomposite with stronger magnetic performance. Poly(acrylic acid) (PAA) oligomer was first reacted with hydroxyl‐functionalized MWCNTs (MWCNTs‐OH) forming PAA‐grafted MWCNTs (PAA‐g‐MWCNTs). Subsequently, Fe₃O₄ nanoparticles were attached onto the surface of PAA‐g‐MWCNTs through an amidation reaction between the amino groups on the surface of Fe₃O₄ nanoparticles and the carboxyl groups of PAA. Fourier transform infrared spectra confirmed that the Fe₃O₄ nanoparticles and PAA‐g‐MWCNTs were indeed chemically linked. The morphology of the nanocomposites was characterized using transmission electron microscope (TEM). The surface and bulk structure of the nanocomposites were examined using X‐ray diffraction, X‐ray photoelectron spectrometer (XPS), and thermogravimetric analysis (TGA). The magnetic performance was characterized by vibrating sample magnetometer (VSM) and the magnetic saturation value of the magnetic nanocomposites was 47 emu g^?1. The resulting products could be separated from deionized water under an external magnetic field within about 15 s. Finally, the magnetorheological (MR) performances of the synthesized magnetic nanocomposites and pure Fe₃O₄ nanoparticles were examined using a rotational rheometer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A Sensitive Electrochemical Sensor Based on Graphene Oxide Nanosheets Decorated by Fe3O4@Au Nanostructure Stabilized on Polypyrrole for Efficient Triclosan Sensing

Triclosan is broadly utilized as preservative or antiseptic in various cosmetic and personal care products. It becomes hazardous for environmental safety and human health more than a certain concentration. In this research, graphene oxide (GO) nanosheets were prepared by composing Fe₃O₄@Au nanostructure decorated GO together with polypyrrole (PPy) (Fe₃O₄@Au‐PPy/GO nanocomposite) in a facile way. The composite excellent increased the electrochemical response, presenting a high sensitive electrochemical method for triclosan detection. The synthesized Fe₃O₄@Au‐PPy/GO nanocomposite was characterized for its morphological, magnetically and structural properties by FESEM‐mapping, TEM, and XRD. The Fe₃O₄@Au‐PPy/GO nanocomposites modified glassy carbon electrodes (GCE), Fe₃O₄@Au‐PPy/GO GCE, showed a higher sensitivity good stability, reproducibility, lower LOD (2.5×10^?9 M) and potential practical application in electrochemical detection of triclosan under optimized experimental conditions.     

Effect of polyol structure on the properties of the resultant magnetic polyurethane elastomer nanocomposites

In this study, two types of magnetic polyurethane (PU) elastomer nanocomposites using polycaprolactone (PCL) and polytetramethylene glycol (PTMG) as polyols were synthesized by incorporating thiodiglycolic acid surface modified Fe₃O₄ nanoparticles (TSM‐Fe₃O₄) into PU matrices through in situ polymerization method. TSM‐Fe₃O₄ nanoparticles were prepared using in situ coprecipitation method in alkali media and were characterized by X‐ray diffraction, Fourier Transform Infrared Spectrophotometer, Transmission Electron Microscopy, and Vibrating Sample Magnetometer. The effects of PCL and PTMG polyols on the properties of the resultant PUs were studied. The morphology and dispersion of the nanoparticles in the magnetic nanocomposites were studied by Scanning Electron Microscope. It was observed that dispersion of nanoparticles in PTMG‐based magnetic nanocomposite was better than PCL‐based magnetic nanocomposite. Furthermore, the effect of polyol structure on thermal and mechanical properties of nanocomposite was investigated by Thermogravimetric Analysis and Dynamic Mechanical Thermal Analysis. A decrease in the thermal stability of magnetic nanocomposites was found compared to pure PUs. Furthermore, DMTA results showed that increase in glass transition temperature of PTMG‐based magnetic nanocomposite is higher than PCL‐based magnetic nanocomposite, which is attributed to better dispersion of TSM‐Fe₃O₄ nanoparticles in PTMG‐based PU matrix. Additionally, magnetic nanocomposites exhibited a lower level of hydrophilicity compared to pure PUs. These observations were attributed to the hydrophobic behavior of TSM‐Fe₃O₄ nanoparticles. Moreover, study of fibroblast cells interaction with magnetic nanocomposites showed that the products can be a good candidate for biomedical application. Copyright © 2013 John Wiley & Sons, Ltd.     

Bio‐based hyperbranched polyurethane/Fe3O4 nanocomposites as shape memory materials

The bio‐based shape memory polymers have generated immense interest as advanced smart materials. Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/Fe₃O₄ nanocomposites were prepared by the in‐situ polymerization technique. The transmission electron microscopy confirmed the homogeneous distribution of the Fe₃O₄ nanoparticles in polymer matrix, whereas Fourier transform infrared spectroscopic study revealed the presence of strong interfacial interactions between them. The incorporation of Fe₃O₄ (0 to 10 wt%) into the HBPU resulted in an increase in tensile strength (5.5–15 MPa) and scratch resistance (3–6 kg). The thermo‐gravimetric analysis indicated the improvement of thermal stability (240–270°C) of the nanocomposites. The nanocomposites exhibited full shape fixity, as well as almost full shape recovery under the microwave stimulus. The shape recovery speed increased with the increase of Fe₃O₄ nanoparticles content in the nanocomposites. Thus, the studied nanocomposites might be used as advanced shape memory materials in different potential fields. Copyright © 2013 John Wiley & Sons, Ltd.     

Monodisperse superparamagnetic pH‐sensitive single‐layer chitosan hollow microspheres with controllable structure

Facile strategy was developed for the fabrication of the monodisperse superparamagnetic pH‐sensitive single‐layer chitosan (CS) hollow microspheres with controllable structure. The carboxyl group‐functionalized polystyrene microspheres prepared by soap‐free emulsion polymerization were used as the templates. After the Fe₃O₄ nanoparticles were in situ formed onto the surface of the templates, the single‐layer CS was self‐assembled and cross‐linked with glutaraldehyde subsequently. Then, the magnetic single‐layer CS hollow microspheres were obtained after the templates were removed. It was found that the feeding ratio of the monomer acrylic acid in the soap‐free emulsion polymerization had played an important role on the particle size and surface carboxyl group content of the templates, which determined the particle size and shell thickness of the magnetic single‐layer CS hollow microspheres in the proposed strategy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Self‐emulsion polymerization of amphiphilic monomers—a green route to synthesis of polymeric nanoscaffolds

Self‐emulsion polymerization (SEP), a green route developed by us for the polymerization of amphiphilic monomers, does not require any emulsifier or an organic solvent except that the water‐soluble initiators such as 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane]dihydrochloride (VA‐044) and potassium persulfate (KPS) are only used. We report here the polymer nanoscaffolds from a number of amphiphilic monomers, which can be used for in situ encapsulation of a variety of nanoparticles. As a demonstration of the efficacy of these nanoscaffolds, the synthesis of a biocompatible hybrid nanoparticle (nanohybrid), prepared by encapsulating Fe₃O₄ magnetic nanoparticle (Fe₃O₄ MNPs) in poly(2‐hydroxyethyl methacrylate) in water, for MRI application is presented. The nanohybrid prepared following the SEP in the form of an emulsion does not involve the use of any stabilizing agent, crosslinker, polymeric emulsifier, or surfactant. This water‐soluble, spherical, and stable nanohybrid containing Fe₃O₄ MNPs of average size 10 ± 2 nm has a zeta potential value of ?41.89 mV under physiological conditions. Magnetic measurement confirmed that the nanohybrid shows typical magnetic behavior having a saturation magnetization (Ms) value of 32.3 emu/g and a transverse relaxivity (r2) value of 29.97 mM^?1 s^?1, which signifies that it can be used as a T2 contrast agent in MRI. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019     

Synthesis and characterization of poly(ɛ-caprolactone)/Fe3o4 nanocomposites by in situ polymerization

A series of magnetic nanocomposites based on poly(?-caprolactone) (PCL) and Fe₃O₄ nanoparticles were prepared using a facile in situ polymerization method. The chemical structures of the PCL/Fe₃O₄ nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. Results of wide-angle X-ray diffraction (WAXD) showed that the incorporation of the Fe₃O₄ nanoparticles did not affect the crystallization structure of the PCL. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the morphology and dispersion of the Fe₃O₄ nanoparticles within the as-synthesized nanocomposites. Results of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) showed that the crystallization temperature was raised and the spherulites size decreased by the presence of Fe₃O₄ nanoparticles in the nanocomposites due to the heterogeneous nucleation effect. The thermal stability of the PCL was depressed by incorporation of Fe₃O₄ nanoparticles from thermogravimetric analysis (TGA). The superparamagnetic behavior of the PCL/Fe₃O₄ nanocomposites was testified by the superconducting quantum interference device (SQUID) magnetometer analysis. The obtained biodegradable nanocomposites will have a great potential in magnetic resonance imaging contrast and targeted drug delivery.     

Synthesis of magnetic,reactive, and thermoresponsive Fe3O4 nanoparticles via surface‐initiated RAFT copolymerization of N‐isopropylacrylamide and acrolein

A reversible addition‐fragmentation chain transfer (RAFT) agent was directly anchored onto Fe₃O₄ nanoparticles in a simple procedure using a ligand exchange reaction of S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate with oleic acid initially present on the surface of pristine Fe₃O₄ nanoparticles. The RAFT agent‐functionalized Fe₃O₄ nanoparticles were then used for the surface‐initiated RAFT copolymerization of N‐isopropylacrylamide and acrolein to fabricate structurally well‐defined hybrid nanoparticles with reactive and thermoresponsive poly(N‐isopropylacrylamide‐co‐acrolein) shell and magnetic Fe₃O₄ core. Evidence of a well‐controlled surface‐initiated RAFT copolymerization was gained from a linear increase of number‐average molecular weight with overall monomer conversions and relatively narrow molecular weight distributions of the copolymers grown from the nanoparticles. The resulting novel magnetic, reactive, and thermoresponsive core‐shell nanoparticles exhibited temperature‐trigged magnetic separation behavior and high ability to immobilize model protein BSA. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 542–550, 2010     

Synthesis and characteristics of poly(N‐isopropylacrylamide‐co‐methacrylic acid)/Fe3O4 thermosensitive magnetic composite hollow latex particles

In this study, the poly(NIPAAm–MAA)/Fe₃O₄ hollow latex particles were synthesized by three steps. The first step was to synthesize the poly(methyl methacrylate‐co‐methylacrylate acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first step, the second step was to polymerize N‐isopropylacrylamide (NIPAAm), MAA, and crosslinking agent (N,N'‐methylene‐bisacrylamide (MBA)) in the presence of poly(MMA‐MAA) latex particles to form the linear poly(MMA‐MAA)/crosslinking poly (NIPAAm‐MAA) core‐shell latex particles. After the previous processes, the core‐shell latex particles were heated in the presence of NH₄OH to dissolve the linear poly(MMA‐MAA) core in order to form the poly(NIPAAm‐MAA) hollow latex particles. In the third step, Fe²⁺ and Fe³⁺ ions were introduced to bond with the ? COOH groups of MAA segments in the poly(NIPAAm‐MAA) hollow polymer latex particles. Further by a reaction with NH₄OH and then Fe₃O₄ nanoparticles were generated in situ and the poly(NIPAAm‐MAA)/Fe₃O₄ magnetic composite hollow latex particles were formed. The concentrations of MAA, crosslinking agent (N,N'‐methylene bisacrylamide), and Fe₃O₄ nanoparticles were important factors to influence the morphology of hollow latex particles and lower critical solution temperature of poly(NIPAAm–MAA)/Fe₃O₄ magnetic composite hollow latex particles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Glass‐transition temperature behavior of alumina/PMMA nanocomposites

Alumina/poly(methyl methacrylate) (PMMA) nanocomposites were synthesized by an in situ free‐radical polymerization process with 38 and 17 nm diameter γ‐alumina nanoparticles. At extremely low filler weight fractions (<1.0 wt % of 38 nm fillers or < 0.5 wt % of 17 nm fillers) the glass‐transition temperature (T_g) of the nanocomposites drops by 25 °C when compared to the neat polymer. Further additions of filler (up to 10 wt %) do not lead to additional T_g reductions. The thermal behavior is shown to vary with particle size, but this dependence can be normalized with respect to a specific surface area. The nanocomposite T_g phenomenon is hypothesized to be because of nonadhering nanoparticles that serve as templates for a porous system with many internal interfaces that break up the percolating structure of dynamically heterogeneous domains recently suggested by Long, D.; and Lequeux, F. Eur Phys J E 2001, 4, 371 to be responsible for the T_g reductions in polymer ultrathin films. The results also point to a far field effect of the nanoparticle surface on the bulk matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4371–4383, 2004     

Organic–inorganic polypyrrole‐surface modified SiO2 hybrid nanocomposites: a facile and green synthetic approach

Organic–inorganic hybrid nanocomposites composed of conductive polypyrrole (PPy) and surface modified silica (SiO₂) were successfully prepared through an in situ chemical oxidative polymerization in supercritical carbon dioxide (scCO₂). SiO₂ nanoparticles were surface modified using 3‐methacryloxypropyltrimethoxysilane (MPTMS) in order to disperse well in the medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the SiO₂ nanoparticles were encapsulated into the polymer. UV‐visible spectra of the diluted colloidal dispersions of PPy/SiO₂ hybrid nanocomposites were similar to those of PPy system. Fourier transform infrared spectroscopy (FT‐IR) suggested the strong interaction between PPy and SiO₂. Surface characterizations of nanocomposites were described by X‐ray photoelectron spectroscopy (XPS). The nanocomposites synthesized in scCO₂ have been shown to possess higher electrical conductivity and thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.     

One Step Preparation of Reduced Graphene Oxide/Pd–Fe3O4@Polypyrrole Composites and Their Application in Catalysis

The simple preparation of catalysts with superior catalytic activity and good reusability is highly desirable. Herein, we report a novel strategy to construct reduced graphene oxide (rGO)/Pd–Fe₃O₄@polypyrrole (PPy) catalysts with Pd and Fe₃O₄ nanoparticles anchored on a rGO nanosheet surface and wrapped in a PPy shell. The synthesis and assembly of both the Pd and Fe₃O₄ nanoparticles, the preparation of the PPy layer, and the reduction of graphene oxide nanosheets were finished in one step. In the system, the PPy layer not only prevented aggregation of Pd and Fe₃O₄ nanoparticles, but also generated a synergistic effect with precursor Pd²⁺ ions, which led to a high dispersity of as‐prepared Pd nanoparticles. Although the procedure was simplified to one step, the catalytic activity and reusability were not sacrificed. In the reduction of 4‐nitrophenol, their catalytic performance was better than that in recent reports. Moreover, the catalysts showed good reusability owing to their magnetic properties.     

Superparamagnetic pH‐sensitive multilayer hybrid hollow microspheres for targeted controlled release

The superparamagnetic multilayer hybrid hollow microspheres have been fabricated using the layer‐by‐layer assembly technique by the electrostatic interaction between the polyelectrolyte cation chitosan (CS) and the hybrid anion citrate modified ferroferric oxide nanoparticles (Fe₃O₄‐CA) onto the sacrificial polystyrene sulfonate microspheres templates after etching the templates by dialysis. The saturation magnetization and magnetite contents of the superparamagnetic multilayer hybrid hollow microspheres were 32.46 emu/g and 51.3%, respectively. The hybrid hollow microspheres showed pH‐sensitive characteristics. The adsorption and release of the basic dye (methylene blue) were applied to investigate the interaction between the amino groups of CS and the carboxyl groups of the Fe₃O₄‐CA nanoparticles in different pH media. The superparamagnetic pH‐sensitive multilayer hybrid hollow microspheres are expected to be used for the targeted controlled release of drugs or in diagnostics. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3135–3144, 2010     

Structure and electrochemical properties of magnetite and polypyrrole nanocomposites formed by pyrrole oxidation with magnetite nanoparticles

Nanocomposite of magnetic Fe₃O₄ nanoparticles and polypyrrole was prepared under sonication by a new chemical polymerization method during which Fe₃O₄ nanoparticles acted both as a pyrrole oxidant and as a component in the composite material. Synthesis of this nanocomposite was carried out in aqueous solution acidified to pH 2, a prerequisite for the formation of these types of material and to facilitate pyrrole oxidation by Fe₃O₄ nanoparticles. In this way, two kind of materials were produced: Fe₃O₄/PPy nanocomposite in which magnetite nanoparticles were dispersed in PPy matrix and Fe₃O₄-aggregates@PPy nanocomposite that exhibits structure in which aggregates of magnetite nanoparticles are surrounded by a layer of polymeric phase. In the latter case, the polymerization process took place in the presence of a surfactant. These nanocomposites were characterized by electron microscopy techniques, IR spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and thermogravimetry. Particular attention was focused on the study of the electrochemical properties of the formed composites. The composite of Fe₃O₄ and PPy exhibits reversible electrochemical behaviour upon oxidation. The electrode process of the polymeric component oxidation in organic solvents such as acetonitrile and dichloromethane is very similar to the process in an aqueous solution.

     

A simple approach for synthesis of hollow mesoporous nanotubes loaded with metallic and magnetic nanoparticles: Only one step is required

Hollow mesoporous polypyrrole (PPy)@Pd‐Fe₃O₄ nanotubes were prepared using MoO₃ nanorods as hard templates in one step, in which construction of PPy nanotubes, preparation of Pd nanoparticles, synthesis of Fe₃O₄ nanoparticles and removal of MoO₃ nanorods were combined together. To the best of our knowledge, this is the simplest approach for the synthesis of nanomaterials with catalytic activity, magnetic property and hollow mesoporous structure simultaneously. Although the preparation procedure was simplified, the catalytic activity and magnetic property were not sacrificed. In the catalytic reduction of 4‐nitrophenol, both reaction rate constant and turnover frequency were higher than those of previous reports. Importantly, the nanotubes could be easily separated from the reaction solution in the presence of a magnetic field, and saturation magnetization could be controlled by the amount of pyrrole monomer. After six recycles, the catalytic activity maintained 94.8% of that of the first run, indicating good stability and reusability.