Electrically conductive polypyrrole (PPy)/poly(methyl methacrylate) (PMMA) core-shell nanoparticles were synthesized by two-step microemulsion polymerization. PPy core particles were prepared in a four-component microemulsion system, which was formed with surfactant cetyltrimethyl ammonium bromide (CTAB), cosurfactant n-pentanol, water, and pyrrole. Ferric chloride and iodine was added as the oxidant and the dopant, respectively. Then the PPy nanoparticles were coated with PMMA to prepare PPy/PMMA core-shell nanoparticles. The morphology of PPy/PMMA core-shell nanoparticles was characterized with transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy was used to characterize the structure of the samples. The electrical conductivities of samples were studied by a Hall effect testing instrument. Despite being coated with a layer of insulation, the conductivity of the composite PPy/PMMA core-shell nanoparticles could still reached to 7.856 × 10?1 S/cm. 相似文献
ABSTRACT Immobilization of yeast cells (Saccharomyces cerevisiae) in different polymer matrices was performed by constant potential electrolysis. These matrices were polypyrrole (PPy); poly(methyl methacrylate)/polypyrrole (PMMA/PPy) and thiophene-capped poly(methyl methacrylate)/polypyrrole (TPMMA/PPy). The characterization of PMMA/PPy copolymer was achieved by Fourier-transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The invertase activity of immobilized yeast cells was determined. Optimum temperature, Michaelis-Menten constants and maximum reaction rates of the enzyme electrodes were compared with those of free yeast cells. The operational and storage stabilities of three different immobilization systems were analyzed. 相似文献
By using a surface-modified templating method, Fe(2)O(3)@polypyrrole (PPy) core/shell spindles have been successfully prepared in this paper. The Fe(2)O(3) particles with spindle morphology were initially fabricated as core materials. After the PVP modification, the Fe(2)O(3) spindles were subsequently coated with a tunable thickness layer of PPy by in situ deposition of the conducting polymer from aqueous solution. Hollow PPy spindles were produced by dissolution of the Fe(2)O(3) core from the core/shell particles. High-temperature treatment under vacuum condition covert the hollow PPy spindles into carbon capsules by carbonization of the PPy shell. Transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of the Fe(2)O(3)@PPy core/shell particles, PPy and carbon capsules with spindle morphology. 相似文献
Carbon nanofibers with new structural features, e.g. nanoporosity, hollow, U-shape cross-section, were generated by utilizing the phase separation behavior of polymer additive with polyacrylonitrile (PAN). The approach involved the formation of precursor fibers by electrospinning of binary mixtures of PAN with poly(ethylene oxide) (PEO), cellulose acetate (CA) or poly(methyl methacrylate) (PMMA), the removal of the polymer and the carbonization of the remaining PAN. The carbon nanofiber yield was ca 50% of PAN in all cases. Nanoporous carbon nanofibers with an average diameter of 100 nm were generated from the water treated PAN/PEO precursors. Multi-channel hollow fibers (90-190 nm diameters) were produced from the acetone treated PAN/CA precursors. Carbon fibers produced from the chloroform treated PAN/PMMA precursors were 250-400 nm in diameters and consisted of varied hollow structures, i.e., hollow and U-shape cross-sections from those containing 30% and 50% PAN, respectively, and multi-channel hollow fibers from the 70/30 PAN/PMMA precursor. Carbonization of equal-mass PAN/PMMA as-spun fibers also produced similarly U-shape cross-sections as the chloroform treated ones, showing promise of direct carbonization. This simple and yet versatile approach to create new structural features in carbonized fibers has shown to depend on the distinct phase separation as well as the pyrolytic behaviors of the second polymer component. 相似文献
We introduce a new approach to pattern conducting polymers by combining oppositely charged conducting polymers on charged self-assembled monolayers (SAMs). The polymer resist pattern behaves as a physical barrier, preventing the formation of SAMs. The patterning processes were carried out using commercially available conducting polymers: a negatively charged PEDOT/PSS (poly(3,4-ethylene-dioxythiophene)/poly(4-stylenesulphonic acid)) and a positively charged polypyrrole (PPy). A bifunctional NH 2 (positively charged) or COOH (negatively charged) terminated alkane thiol or silane was directly self-assembled on a substrate (Au or SiO 2). A suspension of the conducting polymers (PEDOT/PSS and PPy) was then spin-coated on the top surface of the SAMs and allowed to adsorb on the oppositely charged SAMs via an electrostatic driving force. After lift-off of the polymer resist, i.e., poly(methyl methacrylate, PMMA), using acetone, the conducting polymers remained on the charged SAMs surface. Optical microscopy, Auger electron spectroscopy, and atomic force microscopy reveal that the prepared nanolines have low line edge roughness and high line width resolution. Thus, conducting polymer patterns with high resolution could be produced by simply employing charged bifunctional SAMs. It is anticipated that this versatile new method can be applied to device fabrication processes of various nano- and microelectronics. 相似文献
In this article we report the synthesis of polypyrrole incorporated nickel oxide multi walled carbon nanotube (NiO@NMWCNT/PPy) composites by thermal reduction protocol for supercapacitor applications. The structural and morphological properties of the composites were confirmed by the aid of X-ray diffraction (XRD), Field-emission scanning electron microscope (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and Field-emission transmission electron microscopy (FE-TEM) analysis indicating the hexagonal crystal structure of NiO decorated on NMWCNT/Ppy. The electrochemical characteristics of the NiO@MWCNT/PPy composite were analyzed in the presence of 2 M KOH as an electrolyte. The NiO@NMWCNT/PPy nanostructured composite produced a plenty of active sites for ion migration reactions that facilitate the energy storage mechanism. As a proof of concept demonstration, the NiO@NMWCNT/PPy composite was explored as an electrode materials in supercapacitor and exhibited specific capacitance of 395 F g−1 and cyclic stability up to 5000 cycles at 0.5 A g−1. Enhanced performance of composite is attributed to the incorporation of polypyrrole in NiO@NMWCNT. The improved capacitance and cyclic stability demonstrated by the composite indicates the NiO@NMWCNT/PPy to be a promising candidate for supercapacitor applications. 相似文献
Electrospinning is a simple and convenient technique to produce polymer fibers with diameters ranging from several nanometers to a few micrometers. Different types of polymer fibers have been prepared by electrospinning for various applications. Among different post‐treatment methods of electrospun polymer fibers, the annealing process plays a critical role in controlling the fiber properties. The morphology changes of electrospun polymer fibers under annealing, however, have been little studied. Here we investigate the annealing effect of electrospun poly(methyl methacrylate) (PMMA) fibers and their transformation into PMMA microspheres. PMMA fibers with an average size of 2.39 μm are first prepared by electrospinning a 35 wt% PMMA solution in dimethylformamide. After the electrospun fibers are thermally annealed in ethylene glycol, a non‐solvent for PMMA, the surfaces of the fibers undulate and transform into microspheres driven by the Rayleigh instability. The driving force of the transformation process is the minimization of the interfacial energy between the polymer fibers and ethylene glycol. The sizes of the microspheres fit well with the theoretical predictions. Longer annealing times are found to be required at lower temperatures to obtain the microspheres. 相似文献
Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a surfactant mediated sol-gel method followed by a carbonization process. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were produced by a wet-type beadsmill method. To obtain Si-CNT nanocomposites with spherical morphologies, a silica precursor (tetraethylorthosilicate, TEOS) and polymer (PMMA) mixture was employed as a structure-directing medium. Thus the Si-CNT/Silica-Polymer microspheres were prepared by an acid catalyzed sol-gel method. Then a carbon precursor such as polypyrrole (PPy) was incorporated onto the surfaces of pre-existing Si-CNT/silica-polymer to generate Si-CNT/Silica-Polymer@PPy microspheres. Subsequent thermal treatment of the precursor followed by wet etching of silica produced Si-CNT@C microcapsules. The intermediate silica/polymer must disappear during the carbonization and etching process resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests. 相似文献
New electrospun (ES) sensory fibers consisted of poly(methyl methacrylate) (PMMA) core and poly(3-hexylthiophene-2,5-diyl) (P3HT) shell were successfully prepared using a two-fluid coaxial electrospinning process. Field-emission scanning electron microscope (FE-SEM) studies showed that the prepared ES fibers had diameters of 500–700 nm and worm-like surface structure of P3HT on the fiber. Red emission fibers were exhibited from the laser confocal microscope. Upon exposed to air under light for two weeks, significant blue-shifting on both absorption and luminescence spectra was found on the prepared ES fibers. It was probably due to the chain scission occurred in the P3HT and led to the reduced conjugated length. The sensitivity of the ES fibers was much better than that of the spin-coated P3HT film from the comparison on the variation of photophysical properties. Besides, the EPR result indicated the formation of the P3HT · O2 charge transfer complex (CTC), leading to the fiber conductivity of 10−6 S/cm without an external doping. The present study demonstrates that conjugated polymer based ES core-shell fibers may have potential applications for oxygen-sensing devices. 相似文献
The more sensitive and rapid ammonia gas sensors were prepared with nanocomposites of polypyrrole (PPy) and graphitic materials such as graphite, graphite oxide (GO), and reduced graphene oxide (RGO). Pyrrole was polymerized uniformly on the surface of graphitic materials by in situ polymerization method. The structures of nanocomposites were studied by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy indicating the well-exfoliated GO and RGO in PPy matrix with favorable interfacial interaction. PPy/RGO nanocomposite showed the highly improved response in detecting ammonia gas mainly due to the effective electron charge transfer between PPy and ammonia and the efficient transfer of electrical resistance variation by the uniformly dispersed conductive RGO in PPy. PPy/RGO nanocomposite gas sensor also showed the excellent reproducibility in ammonia sensing behavior during the recovery process at lower temperature of 373 K. 相似文献
Electrospun core–shell fibers have great potentials in many areas, such as tissue engineering, drug delivery, and organic solar cells. Although many core–shell fibers have been prepared and studied, the morphology transformation of core–shell fibers have been rarely studied. In this work, the morphology evolution of electrospun core–shell polymer fibers driven by the Plateau–Rayleigh instability is investigated. Polystyrene/poly(methyl methacrylate) (PS/PMMA) core–shell fibers are first prepared by using blend solutions and a single axial electrospinning setup. After PS/PMMA core–shell fibers are annealed on a PS film, the fibers undulate and sink into the polymer film, forming core–shell hemispheres. The evolution process, which can be observed in situ by optical microscopy, is mainly driven by achieving lower surface and interfacial energies. The morphologies of the transformed structures can be confirmed by a selective removal technique, and polymer microbowls can be obtained.
Atomic force microscopy (AFM) is employed to monitor the surface morphology of polypyrrole (PPy) films grown on vitreous carbon substrates during the catalytic reduction of Cr(VI) to Cr(III). The morphology of freshly-prepared films depends on substrate characteristics. Upon reaction, uniform nodules of aggregated PPy clusters appear. No significant differences in surface morphology are found between its oxidized and reduced forms. Loss of catalytic activity after 8-9 oxidation/reduction cycles of exposure to the chromate solution (oxidation) and electrochemical recharging of the film at negative potentials (reduction) correlates well with the observed polymer film dissolution/detachment from the carbon substrate. Formation of well-defined circular features (PPy rings) at different stages leads to a model for the film degradation process that includes formation of Cl2 gas inside the polymer matrix. In the final stages, the bulk of the film typically fractures and detaches from the electrode. A catalytically inactive, ultrathin PPy layer remains on the substrate even after prolonged exposure to the target solution. A review of techniques for the study of PPy aging/degradation is given. 相似文献