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Continuous nickel oxide (NiO) nanocomposite layer on flexible polyimide (PI) substrate was prepared via an ion exchange technique. First, nickel(Pi) poly(amate) layers were formed on both surfaces of PI film through chemical surface modification of PI films in aqueous NaOH solution and then ion exchange in aqueous NiSO4 solution. Subsequently, hydrothermal treatment of the Ni2+-loaded PI films in an aqueous urea solution led to Ni(OH)2 formation in the surface-modified layers. Final thermal annealing in ambient air made Ni(OH)2 decompose to NiO, which diffused and aggregated to give continuous layers on both surfaces of PI film. The composite films were characterized by XRD, XPS, SEM, TEM, TGA, and DSC, respectively. Results from SEM and TEM measuring revealed that the NiO layers consisted of NiO nanoparticles with diameter ranging from 10 to 15 nm. Thermal properties of PI/NiO nanocomposite films were similar to those of host PI. This paper provides an effective methodology for the preparation of polymer/metal oxide nanocomposite films, which hold great promise toward the potential application in the areas of flexible microsensors and devices.
ACS Appl Mater Interfaces 2010 Jan
PMID:Fabrication of nickel oxide nanocomposite layer on a flexible polyimide substrate via ion exchange technique. 2035 27

Electrostatic layer-by-layer assembly was the basis for the synthesis of multilayer nanorod/polymer composite films. Cationic and water-soluble CdSe nanorods (NRs) were synthesized and partnered with anionic polymers including poly(sodium 4-styrenesulfonate) (PSS) and two polythiophene-based photoactive polymers, sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate (PTEBS) and poly[3-(potassium-6-hexanoate)thiophene-2,5-diyl] (P3KHT). Controlled multilayer growth is shown through UV-vis spectroscopy, cross-sectional SEM and surface analytical techniques including atomic force microscopy. The formation of an intimate nanorod/conducting polymer bulk heterojunction is confirmed through cross-sectional SEM, TEM, and scanning Auger analysis. A series of photovoltaic devices was fabricated on ITO electrodes using CdSe NRs in combination with PTEBS or P3KHT. A thorough device analysis showed that performance was limited by low short circuit current although charge transfer was confirmed in the ELBL nanocomposite thin films.
ACS Appl Mater Interfaces 2010 Jan
PMID:Electrostatic layer-by-layer assembly of CdSe nanorod/polymer nanocomposite thin films. 2035 38

Hybrid nanocomposites containing carbon nanotubes (CNTs) and ordered polyaniline (PANI) have been prepared through an in situ polymerization reaction using a single-walled nanotube (SWNT) as template and aniline as reactant. TEM, SEM, XRD, and Raman analyses show that the polyaniline grew along the surface of CNTs forming an ordered chain structure during the SWNT-directed polymerization process. The SWNT/PANI nanocomposites show both higher electrical conductivity and Seebeck coefficient as compared to pure PANI, which could be attributed to the enhanced carrier mobility in the ordered chain structures of the PANI. The maximum electrical conductivity and Seebeck coefficient of composites reach 1.25 x 10(4) S m(-1) and 40 microV K(-1), respectively, and the maximum power factor is up to 2 x 10(-5) W m(-1) K(-2), more than 2 orders of magnitude higher than the pure polyaniline. This study suggests that constructing highly ordered chain structure is a novel and effective way for improving the thermoelectric properties of conducting polymers.
ACS Nano 2010 Apr 27
PMID:Enhanced thermoelectric performance of single-walled carbon nanotubes/polyaniline hybrid nanocomposites. 2035 34

CuO nanocrystalline powder was synthesized by a sol-gel auto combustion route with different amounts of the cetyltrimethylammonium bromide (CTAB) used as cationic surfactant. The samples were characterized by XRD, FESEM, and TEM techniques. The electrical properties of the samples without and with different CTAB concentration and the response to ammonia gas at room temperature have been investigated. The CTAB appears to influence the morphology and the properties of CuO powder. The lattice constant values of the samples indicate monoclinic structure. TEM indicate the crystallite size around 7 nm for the CuO with 0.5M CTAB. The addition of surfactant results in an increase in the response of CuO thick films for ammonia at room temperature.
ACS Appl Mater Interfaces 2010 May
PMID:Room-temperature ammonia sensor based on cationic surfactant-assisted nanocrystalline CuO. 2040 66

ZnO nanostructures were deposited on flexible polymer sheet and cotton fabrics at room temperature by activated reactive evaporation. Room-temperature photoluminescence spectrum of ZnO nanostructured film exhibited a week intrinsic UV emission and a strong broad yellow-orange visible emission. TEM and HRTEM studies show that the grown nanostructures are crystalline in nature and their growth direction was identified to be along [002]. ZnO nanostructures grown on the copper-coated flexible polymer sheets exhibited stable field-emission characteristics with a threshold voltage of 2.74 V/mum (250 muA) and a very large field enhancement factor (beta) of 23,213. Cotton fabric coated with ZnO nanostructures show an excellent antimicrobial activity against Staphylococcus aureus bacteria (Gram positive), and approximately 73% reduction in the bacterial population is achieved compared to uncoated fabrics after 4 h in viability. Using a shadow mask technique, we also selectively deposited the nanostructures at room temperature on polymer substrates.
ACS Appl Mater Interfaces 2010 Apr
PMID:Optical, field-emission, and antimicrobial properties of ZnO nanostructured films deposited at room temperature by activated reactive evaporation. 2042 21

The photochemical method is a convenient and simple way to synthesize the polymer brush on surface. We presented here a facile approach to fabricate PMMA brush on silica particles (SPs) by combination of self-assembly monolayer of hyperbranched polymeric thioxanthone (HPTX) and surface-initiated photopolymerization (SIPP). HPTX was immobilized on the surface of silica particles (SPs) through nucleophilic addition between amine and epoxy groups, and then initiated photopolymerization of MMA to generate PMMA brush on SPs at room temperature. The whole process was well-traced by FT-IR, TGA, SEM, and TEM. The results show that it is easy to create PMMA brushes of tunable thickness under UV irradiation. Especially, TEM images reveal the obvious formation of well-defined hybrid particles with SPs as the core and PMMA layers as the shell. The obtained hybrid particles can be implanted into PMMA matrix to produce PMMA composite with enhanced thermal and mechanical properties.
ACS Appl Mater Interfaces 2010 Apr
PMID:Well-defined PMMA brush on silica particles fabricated by surface-initiated photopolymerization (SIPP). 2042 23

Polymer-derived ceramic fibers with aligned multiwalled carbon nanotubes (MWCNTs) are fabricated through the electrospinning of polyaluminasilazane solutions with well-dispersed MWCNTs followed by pyrolysis. Poly(3-hexylthiophene)-b-poly (poly (ethylene glycol) methyl ether acrylate) (P3HT-b-PPEGA), a conjugated block copolymer compatible with polyaluminasilazane, is used to functionalize MWCNT surfaces with PPEGA, providing a noninvasive approach to disperse carbon nanotubes in polyaluminasilazane chloroform solutions. The electrospinning of the MWCNT/polyaluminasilazane solutions generates polymer fibers with aligned MWCNTs where MWCNTs are oriented along the electrospun jet by a sink flow. The subsequent pyrolysis of the obtained composite fibers produces ceramic fibers with aligned MWCNTs. The study of the effect of polymer and CNT concentration on the fiber structures shows that the fiber size increases with the increment of polymer concentration, whereas higher CNT content in the polymer solutions leads to thinner fibers attributable to the increased conductivity. Both the SEM and TEM characterization of the polymer and ceramic fibers demonstrates the uniform orientation of CNTs along the fibers, suggesting excellent dispersion of CNTs and efficient CNT alignment via the electrospinning. The electrical conductivity of a ceramic fibers with 1.2% aligned MWCNTs is measured to be 1.58 x 10(-6) S/cm, which is more than 500 times higher than that of bulk ceramic (3.43 x 10(-9) S/cm). Such an approach provides a versatile method to disperse CNTs in preceramic polymer solutions and offers a new approach to integrate aligned CNTs in ceramics.
ACS Appl Mater Interfaces 2010 Apr
PMID:Polymer-derived ceramic composite fibers with aligned pristine multiwalled carbon nanotubes. 2042 34

A method is presented to produce graphene dispersions, stabilized in water by the surfactant sodium cholate, at concentrations up to 0.3 mg/mL. The process uses low power sonication for long times (up to 400 h) followed by centrifugation to yield stable dispersions. The dispersed concentration increases with sonication time while the best quality dispersions are obtained for centrifugation rates between 500 and 2000 rpm. Detailed TEM analysis shows the flakes to consist of 1-10 stacked monolayers with up to 20% of flakes containing just one layer. The average flake consists of approximately 4 stacked monolayers and has length and width of approximately 1 mum and approximately 400 nm, respectively. These dimensions are surprisingly stable under prolonged sonication. However, the mean flake length falls from approximately 1 mum to approximately 500 nm as the centrifugation rate is increased from 500 to 5000 rpm. Raman spectroscopy shows the flake bodies to be relatively defect-free for centrifugation rates below 2000 rpm. The dispersions can be easily cast into high-quality, free-standing films. The method extends the scope for scalable liquid-phase processing of graphene for a wide range of applications.
ACS Nano 2010 Jun 22
PMID:High-concentration, surfactant-stabilized graphene dispersions. 2045 83

Our study demonstrates that the C(69)N azafullerene can be encapsulated inside single-walled carbon nanotubes (SWNTs), which is confirmed by TEM, UV-vis-IR spectroscopy, Raman spectroscopy, and UPS. The electrical transport properties of SWNTs are found to change drastically due to the encapsulated C(69)N azafullerene. Our experimental results indicate that C(69)N encapsulated SWNTs show the high-performance n-type behavior compared with p-type characteristics of pristine SWNTs and C(70) encapsulated SWNTs. This n-type transport characteristic can be explained by the charge transfer effect between SWNTs and encapsulated C(69)N, which can easily lose an electron. The unique electronic properties of C(69)N encapsulated SWNTs make them potentially useful in many applications in engineering functional nanodevices.
ACS Nano 2010 Jun 22
PMID:Synthesis and property characterization of c(69)n azafullerene encapsulated single-walled carbon nanotubes. 2050 15

Split-inteins can be used to generate backbone cyclized peptide as a source of new bioactive molecules. In this work we show that cysteine-mediated splicing can be performed in the oxidative environment of the periplasm of Escherichia coli. Cyclization of the TEM-1 beta-lactamase and of small randomized peptides was demonstrated using an artificially permuted version of the DnaB mini-intein from Synechocystis sp. PCC6803 strain fused to a signal sequence. For small peptides, a signal sequence that promotes cotranslational translocation had to be used. Efficient backbone cyclization was observed for more than 50% of combinatorial peptides featuring a fully randomized sequence inserted between a serine and glycine that are necessary for fast splicing. Furthermore, by coexpressing a mutant of the pIV outer membrane pore protein of fd bacteriophage, we showed that peptides can diffuse in the extracellular medium. These results open new routes for searching compounds acting on new targets such as exported and membrane proteins or pathogen microorganisms.
ACS Chem Biol 2010 Jul 16
PMID:Intein-mediated cyclization of randomized peptides in the periplasm of Escherichia coli and their extracellular secretion. 2052 81


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