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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nanofibers of doped polyaniline.HCSA having diameters 1-2 nm are observed in TEM images of bath sonicated aqueous dispersions of larger nanofibers (30-50 nm diameter) synthesized by surfactant-assisted chemical oxidative polymerization of aniline in dilute aqueous organic acids.
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PMID:Polyaniline nanofibers: chemical synthesis using surfactants. 1549 20

We describe in this paper an easy route to the synthesis of a novel surface-functionalized conducting polyaniline-chitosan nanocomposite. A stable colloidal dispersion was prepared when aniline was polymerized in the presence of chitosan as the steric stabilizer. TEM study shows that these surface-functionalized polyaniline-chitosan nanoparticles have rice-grain morphologies. The effect of reaction parameters on the mean size of the polyaniline-chitosan nanoparticles was studied. The steric electrostatic interaction between segments of these two polymers explains the excellent storage stability of the polyaniline-chitosan dispersion. Reaction parameters were optimized in order to get stable polyaniline-chitosan dispersion. The chemical structures of polyaniline-chitosan nanocomposite were characterized. FT-IR spectra of the polyaniline-chitosan nanocomposite show that there exist a certain interaction between polyaniline and chitosan. X-ray photoelectron spectroscopy spectra show that chitosan is largely present at the surface of polyaniline-chitosan nanoparticles. The electrical conductivity of the polyaniline-chitosan nanocomposite increases with increasing the amount of polyaniline to a high value of 0.25 S/cm.
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PMID:Synthesis and characterization of surface-functionalized conducting polyaniline-chitosan nanocomposite. 1591 57

This work demonstrated a facile route for the synthesis of poly(3,5-dimethyl aniline) nanofibers by polymerization of 3,5-dimethyl aniline using Pd-acetate as the oxidant. The reduction of Pd ion is accompanied by oxidative polymerization of 3,5-dimethyl aniline, leading to a metal-polymer composite material. Palladium nanoparticles (approximately 2 nm) are uniformly distributed throughout the polymer that makes the composite material a unique morphology. The resultant composite material was characterized by means of different techniques. IR and Raman spectra provide the information on the chemical structure of the polymer. TEM images show the morphology of the polymer and size of the metal particles.
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PMID:Fabrication of a metal nanoparticles and polymer nanofibers composite material by an in situ chemical synthetic route. 1608 6

We report herein the template-directed synthesis, characterization, and electric properties of single-walled carbon nanotube- (SWNT-) based coaxial nanowires, that is, core (SWNT)-shell (conducting polypyrrole and polyaniline) nanowires. The SWNTs were first dispersed in aqueous solutions containing cationic surfactant cetyltrimethylammonium bromide (CTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonyl phenyl ether (O pi-10). Each individual nanotube (or small bundle) was then encased in its own micellelike envelope with hydrophobic surfactant groups orientated toward the nanotube and hydrophilic groups orientated toward the solution. And thus a hydrophobic region within the micelle/SWNT (called a micelle/SWNT hybrid template) was formed. Insertion and growth of pyrrole or aniline monomers in this hybrid template, upon removal of the surfactant, produce coaxial structures with a SWNT center and conducting polypyrrole or polyaniline coating. Raman and Fourier transform infrared (FTIR) spectroscopy and scanning (SEM) and transmission (TEM) electron microscopy were used to characterize the composition and the structures of these coaxial nanowires. The results revealed that the micellar molecules used could affect the surface morphologies of the resulting coaxial nanowires but not the molecular structures of the corresponding conducting polymers. Electric properties testing indicated that the SWNTs played the key roles in the conducting polymer/SWNT composites during electron transfer in the temperature range 77 K to room temperature. Compared with the SWNT network embedded in the conducting polymers, the composites within which SWNTs were coated perfectly by the identical conducting polymers exhibited higher barrier heights during electron transfer.
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PMID:Single-walled carbon nanotube-based coaxial nanowires: synthesis, characterization, and electrical properties. 1685 Oct 66

A novel nano-biocomposite of silver and poly(o-methoxy aniline) (POMA)/DNA hybrid has been prepared by adding DNA solution to an aqueous solution of POMA (emeraldine base, EB) and AgNO(3) mixture. The mixture was aged for 10 days and was freeze-dried to form the hybrid nanocomposite (weight fraction of DNA = 0.75). FESEM pictures show a fibrillar network morphology of the biomolecular hybrid with silver nanoparticles on its surface. The TEM picture also corroborates silver nanoparticle formation in the biomolecular hybrid, and the denser population of nanoparticles in the TEM micrograph as compared to that in the SEM micrograph indicates that the nanoparticles are present inside the fibrils in greater proportion. The dc conductivity value of the hybrid indicates that POMA (EB) is doped by silver ion and the doped POMA form complexes with DNA through electrostatic interaction of the radical cation of POMA (emeraldine salt form, ES) and the DNA anion. During the doping process and Ag nanoparticle formation, a fluctuation of the pi band to polaron band transition peak occurs together with a complementary fluctuation of the polaron band to pi* band transition peak. After 53 h of aging, the former shows a slow but continuous red shift with aging time. This has been attributed to the slow uncoiling of POMA on the DNA surface. The conformation and crystal structure of DNA remain intact during the nano-biocomposite formation. The dc conductivity value of the nano-biocomposite is almost the same as that of the pure POMA-DNA hybrid at the same composition, but the I-V characteristic curve of the nano-biocomposite is somewhat different showing an insulating region on low applied voltage. At higher applied voltage, it shows a semiconducting property characterizing the large band gap semiconducting behavior of the nano-biocomposite.
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PMID:Formation of silver nanoparticles in deoxyribonucleic acid-poly(o-methoxyaniline) hybrid: a novel nano-biocomposite. 1697 Apr 49

We report a general and versatile method for controlled synthesis of anisotropic gold nanostructures through the reduction of HAuCl4 by aniline in aqueous solution, without the need for an additional stabilizer or capping agent. In this approach, the reduction kinetics of AuCl-4 can be altered by simply adjusting the initial pH and temperature, inducing the formation of a wide variety of anisotropic nanostructures such as dispersed or multilayered plates, wires with networked or paramecium-like structures, and ginger-shaped particles. AFM, TEM, XRD, EDX, FTIR, and UV-vis-NIR measurements were used to characterize the resulting gold nanostructures. Investigation reveals that in situ formed polyaniline serves effectively as a capping agent to direct the shape of gold nanostructures during the slow growth process. These as-synthesized gold nanostructures exhibit strongly shape-dependent optical properties. This facile approach may be extended to the synthesis of some other anisotropic metal nanostructures such as platinum or palladium.
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PMID:One-step controlled synthesis of anisotropic gold nanostructures with aniline as the reductant in aqueous solution. 1730 Jul 97

Novel covalently porphyrin functionalized single-walled carbon nanotubes (SWNTs) were synthesized using carboxylic group functionalized carbon nanotubes (o-SWNTs) with meso-aniline substituted porphyrin. The structure and morphology of this SWNT nanohybrid material were fully characterized with FTIR, Raman, UV-Vis-NIR spectra as well as TGA and TEM measurements. The energy transfer efficiency from porphyrin to SWNTs and porphyrin fluorescence quenching mechanism were studied by means of steady state fluorescence and time-resolved fluorescence measurement. The fast and efficient electron transfer occurring in this nanohybrid illustrates that they can be utilized as a good candidate for light harvesting materials in molecular photonic devices and solar energy utilization.
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PMID:A nanohybrid material of SWNTs covalently functionalized with porphyrin for light harvesting antenna: synthesis and photophysical properties. 1745 Sep 23

The preparation of CeO2/polyaniline (CeO2/PANI) core-shell nanocomposites via chemical oxidation of aniline using CeO2 as an oxidant is reported. TEM, TGA, FT-IR, XPS, and conductivity measurement are used to characterize the resulting composites. TEM measurements reveal that the shape of PANI/CeO2 nanocomposites is different from CeO2 nanoparticles and fibular PANI oxidized with soluble oxidant. Electron diffraction (ED) patterns of CeO2/PANI nanocomposites reveal single crystal of CeO2. FT-IR spectra confirmed the formation of PANI; the amount of PANI in the nanocomposites is estimated by TGA results. The conductivities increase with the increasing ratio of PANI/CeO2. XPS results reveal that in the nanocomposites Ce4+ of CeO2 is reduced to Ce3+. In addition, the degree of protonation of polyaniline obtained from N 1s XPS results in cerium dioxide/polyaniline composites is about 48.52%.
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PMID:Cerium dioxide/polyaniline core-shell nanocomposites. 1825 85

In this report, a four-component nanocomposite, trypsin-immobilized polyaniline-coated Fe(3)O(4)/carbon nanotube composite, was synthesized for highly efficient protein digestion. Fe(3)O(4) was deposited by the chemical coprecipitation of Fe(2+) and Fe(3+) in an alkaline solution containing carbon nanotubes (CNTs) to prepare nano-Fe(3)O(4)/CNT composite. Subsequently, polyaniline (PA) was assembled on the Fe(3)O(4)/CNT composite by the in situ polymerization of aniline in the presence of trypsin to obtain trypsin-immobilized PA/Fe(3)O(4)/CNT nanocomposite. The novel 1D superparamagnetic biomaterial has been characterized by TEM, SEM, XRD, and magnetometric analysis. The feasibility and performance of the unique magnetic biomaterial have been demonstrated by the tryptic digestion of bovine serum albumin, myoglobin, and lysozyme within 5min. The digests were identified by MALDI-TOF MS with sequence coverages that were comparable to those obtained from the conventional in-solution tryptic digestion. The present biocomposite offers considerable promise for protein analysis due to its high magnetic responsivity and excellent dispersibility. It can be easily isolated from the digests with the aid of an external magnetic field. Because the enzyme-immobilized nanocomposite can be prepared by a simple two-step deposition approach at low cost, it may find a wide range of biological applications including proteome research.
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PMID:Immobilization of trypsin in polyaniline-coated nano-Fe3O4/carbon nanotube composite for protein digestion. 1835 64

Here, we report a synthesis of novel polyaniline nanospheres bearing mono- and bishydroxyl functional groups to trace the molecular interactions at the nanosurfaces through vitamin C sensing. Two new aniline monomers were synthesized via a tailor-made approach and polymerized to produce soluble and uniform polyaniline nanospheres. The structures of the monomers and polymers were characterized by NMR, FT-IR, and MS techniques, and the morphology of the nanomaterials was analyzed by SEM and TEM. The mechanistic aspects of the nanomaterial formations were analyzed by FT-IR and dynamic light scattering techniques. These studies revealed that the hydroxyl-functionalized monomers have strong hydrogen bonding at the monomer level and form spherical aggregates in water, which are templates for the polyaniline nanospheres 600 +/- 100 nm in size. A controlled synthesis was also carried out using aniline hydrochloride as an unsubstituted counterpart, which yields polyaniline nanofibers. WXRD analysis confirmed the presence of a sharp peak at lower angle at 2theta = 7.3 degrees ( d-spacing of 13.4 A) in hydroxyl-substituted nanospheres with respect to enhancement of solid-state ordered crystalline domains, whereas unsubstituted nanofibers were found to be highly amorphous. Vitamin C was employed as an analyte to trace the molecular interaction at the nanosphere surface and study the influence of nanosurface functionalization on the sensing ability of biomolecules. The bishydroxyl-functionalized polyaniline nanospheres were found to show efficient molecular interactions toward vitamin C, whereas nanospheres with a monohydroxyl group or unsubstituted nanofibers failed as sensing materials. In a nut shell, in the present investigation, for the first time, we have proved the importance of surface functionalization of polyaniline nanomaterial, exclusively nanospheres, using hydroxyl groups for studying the molecular interactions at the nanosurfaces with biomolecules such as vitamin C.
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PMID:Hydroxyl-functionalized polyaniline nanospheres: tracing molecular interactions at the nanosurface via vitamin C sensing. 1868 Mar 31


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