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Stable superhydrophobic films with a contact angle of 151 +/- 2 degrees were prepared on zinc substrates by a simple immersion technique into a methanol solution of hydrolyzed 1H,1H,2H,2H-perfluorooctyltrichlorosilane [CF3(CF2)5(CH2)2SiCl3, PFTS] for 5 days at room temperature followed by a short annealing at 130 degrees C in air for 1 h. The superhydrophobic film provides an effective corrosion-resistant coating for the zinc interface when immersed in an aqueous solution of sodium chloride (3% NaCl) for up to 29 days. The corrosion process was investigated by following the change of the water contact angle over time and by electrochemical means. The results are compared to those of unprotected zinc interfaces.
ACS Appl Mater Interfaces 2009 Jun
PMID:Preparation of superhydrophobic coatings on zinc as effective corrosion barriers. 2035 4

The vapor-phase polymerization (VPP) of poly(3-hexylthiophene) (P3HT) was achieved successfully as an alternative method to conventional solution-based thin film fabrication. Using Fe(III)Cl(3).6H(2)O, a spontaneous reaction of 3-hexylthiophene monomers resulted in the rapid formation of conducting P3HT thin films directly on substrates, such as glass, indium-tin-oxide, and poly(ethylene terephthalate), at thicknesses ranging from 50 to 1000 nm. The VPP of P3HT was achieved using ferric chloride hexahydrate and a 1:1 ratio of a methanol/ethanol mixture as the solvent system. The developed VPP technique can provide good processing consistency with an electrical conductivity, a transmittance, and a surface roughness of approximately 10(-2) S/cm, >90%, and <10 nm, respectively.
ACS Appl Mater Interfaces 2009 Jul
PMID:Fabrication of poly(3-hexylthiophene) thin films by vapor-phase polymerization for optoelectronic device applications. 2035 62

The effect of incorporating an organic linking group, 1,6-bis(trimethoxysilyl)hexane (BTMSH), into the underlying silica structure of a styrene cross-linked silica aerogel is examined. Vinyltrimethoxysilane (VTMS) is used to provide a reactive site on the silica backbone for styrene polymerization. Replacement of up to 88 mol % of the silicon from tetramethoxyorthosilicate with silicon derived from BTMSH and VTMS during the making of silica gels improves the elastic behavior in some formulations of the cross-linked aerogels, as evidenced by measurement of the recovered length after compression of samples to 25% strain. This is especially true for some higher density formulations, which recover nearly 100% of their length after compression to 25% strain twice. The compressive modulus of the more elastic monoliths ranged from 0.2 to 3 MPa. Although some of these monoliths had greatly reduced surface areas, changing the solvent used to produce the gels from methanol to ethanol increased the surface area in one instance from 6 to 220 m(2)/g with little affect on the modulus, elastic recovery, porosity, or density.
ACS Appl Mater Interfaces 2009 Mar
PMID:Tailoring elastic properties of silica aerogels cross-linked with polystyrene. 2035 84

A series of new Nafion-based composite membranes have been prepared via an in situ sol-gel reaction of 3-(trihydroxylsilyl)propane-1-sulfonic acid and solution casting method. The morphological structure, ion-exchange capacity, water uptake, proton conductivity, and methanol permeability of the resulting composite membranes have been extensively investigated as functions of the content of sulfopropylated polysilsesquioxane filler, temperature, and relative humidity. Unlike the conventional Nafion/silica composites, the prepared membranes exhibit an increased water uptake and associated enhancement in proton conductivity compared to unmodified Nafion. In particular, considerably high proton conductivities at 80 and 120 degrees C under 30% relative humidity have been demonstrated in the composite membranes, which are over 2 times greater than that of Nafion. In addition to a remarkable improvement in proton conductivity, the composite membranes display lower methanol permeability and superior electrochemical selectivities in comparison to the pure Nafion membrane. These unique properties could be exclusively credited to the presence of pendant sulfonic acid groups in the filler, which provides fairly continuous proton-conducting pathways between filler and matrix in the composite membranes and thus facilitates the proton transport without the anticipated trade-off between conductivity and selectivity. This work opens new opportunities of tailoring the properties of Nafion-the benchmark fuel cell membrane-to obviate its limitations and enhance the conductive properties at high temperature/low humidity and in direct methanol fuel cells.
ACS Appl Mater Interfaces 2009 Nov
PMID:Acid-functionalized polysilsesquioxane-nafion composite membranes with high proton conductivity and enhanced selectivity. 2035 29

Rod and sphere-like CeO(2) particles were obtained via a supercritical solvothermal method using CeCl(3).7H(2)O and Ce(NO(3))(3).6H(2)O as cerium sources in ethanol and methanol at 400 degrees C for 15 min followed by calcination in air. The rodlike particles were 200-400 nm in diameter and 1-2 mum in length. The spherical particles were 300-500 nm in diameter. The as-prepared rodlike particles using CeCl(3).7H(2)O consisted of mixtures of Ce(OH)(3) and Ce(CH(3)COO)(3) and were converted to rodlike CeO(2) by calcination in air at 500 degrees C. In contrast, the spherical particles prepared using Ce(NO(3))(3).6H(2)O consisted of fluorite-structured CeO(2). The possible formation mechanism was discussed on the basis of the effect of reaction time on the morphology at 400 degrees C. The rod- and spherelike CeO(2) particles exhibited strong UV absorption below 400 nm, and the absorbance edges extend to nearly 500 nm. The rod- and spherelike CeO(2) particles exhibited near-UV emission at 360 nm and blue emission at 465 nm with higher emission intensity compared to the commercial CeO(2) sample.
ACS Appl Mater Interfaces 2009 Nov
PMID:Morphology control of cerium oxide particles synthesized via a supercritical solvothermal method. 2035 44

The activity and selectivity of carbon-supported Pt-decorated PdFe nanoparticles in the oxygen reduction reaction (ORR) were investigated in the presence and absence of methanol. The Pt-decorated PdFe nanoparticles, which consist of a PdPt surface and a PdFe interior, were prepared by the galvanic reaction between PdFe/C alloy nanoparticles and PtCl4(2-) in aqueous solution. The presence of a Pt-enriched surface after the replacement reaction was independently confirmed by several microstructural characterization techniques and cyclic voltammetry. The catalyst with such heterogeneous architecture is catalytically more active than a bulk PdFePt alloy catalyst with the same overall composition. The observed enhancements in catalyst performance can be attributed to the lattice strain effect between the shell and core components. The Pt-decorated PdFe (PdFe@PdPt/C) catalyst also compares favorably with a commercial Pt/C catalyst with four times as much Pt in terms of ORR activity, cost, and methanol tolerance.
ACS Appl Mater Interfaces 2010 Jan
PMID:Pt-decorated PdFe nanoparticles as methanol-tolerant oxygen reduction electrocatalyst. 2035 28

Poly(1-(2-methacryloyloxy)ethyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide) (PMIS) and poly(n-hexyl methacrylate) (PHMA) brushes were prepared on initiator-immobilized silicon wafers by surface-initiated atom transfer radical polymerization. The macroscopic frictional properties of the brushes were determined using a ball-on-flat type tribotester under reciprocating motion in a dry nitrogen atmosphere, water, methanol, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTFSI). When the PMIS and PHMA brushes were exposed to EMImTFSI, the friction coefficient of the former was lower than that of the latter. It is thought that the high affinity of the PMIS brush to EMImTFSI led to a reduction in the interaction between the brush and the friction probe, which resulted in a low friction coefficient. The friction force of the PMIS brush in EMImTFSI was proportional to a normal load in the range of 0.2-0.98 N. The friction coefficient gradually decreased to 0.01 with an increase in the sliding velocity from 1 x 10(-4) to 1 x 10(-1) m s(-1). The friction coefficient of the PMIS brush exhibited low magnitude until 800 friction cycles in the dry nitrogen atmosphere, whereas the PHMA brush was abraded away within 150 friction cycles. The XPS spectra of the worn surfaces on the PMIS brush suggested that the brush was gradually abraded by friction.
ACS Appl Mater Interfaces 2010 Apr
PMID:Macroscopic frictional properties of poly(1-(2-methacryloyloxy)ethyl-3-butyl imidazolium bis(trifluoromethanesulfonyl)-imide) brush surfaces in an ionic liquid. 2036 30

A novel ligand, 5-mercaptomethyltetrazole, is applied to the direct colloidal synthesis of highly luminescent (quantum yield of up to 60%) water-soluble CdTe nanocrystals. In the synthesis the 5-mercaptomethyltetrazole behaves analogously to the widely used thioglycolic acid, providing the additional advantage of solubility of the resulting nanocrystals in methanol. Moreover, the 5-mercaptomethyltetrazole-capped nanocrystals possess the unique ability to reversibly form fine 3D networks (hydrogels) upon the addition of metal salts.
ACS Nano 2010 Jul 27
PMID:CdTe nanocrystals capped with a tetrazolyl analogue of thioglycolic acid: aqueous synthesis, characterization, and metal-assisted assembly. 2056 28

The N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) derived silicate matrix supported core-shell TiO(2)-Au nanoparticles (EDAS/(TiO(2)-Au)(nps)) were prepared by NaBH(4) reduction of HAuCl(4) precursor on preformed TiO(2) nanoparticles in the presence of EDAS monomer. The core-shell (TiO(2)-Au)(nps) nanoparticles were stabilized by the amine functional group of the EDAS silicate sol-gel network. The potential application of this EDAS/(TiO(2)-Au)(nps) modified electrode toward the photoelectrochemical oxidation of methanol was explored. The EDAS/(TiO(2)-Au)(nps) modified electrode showed a 12-fold enhancement in the catalytic activity toward photoelectrooxidation of methanol when compared to TiO(2) dispersed in EDAS silicate sol-gel matrix. This improved photoelectrochemical performance is explained on the basis of beneficial promotion of interfacial charge transfer processes of the EDAS/(TiO(2)-Au)(nps) nanocomposite. A methanol oxidation peak current density of 12.3 mA cm(-2) was achieved at an optimum loading of Au(nps) on TiO(2) particles. This novel amine functionalized EDAS silicate sol-gel stabilized core-shell (TiO(2)-Au)(nps) nanomaterial could be an excellent candidate for the photocatalytic and photoelectrochemical applications.
ACS Appl Mater Interfaces 2010 Jul
PMID:Functionalized silicate sol-gel-supported TiO2-Au core-shell nanomaterials and their photoelectrocatalytic activity. 2066 86

Platinum (Pt) nanopetals were electrodeposited on highly ordered silicon nanocones (SiNCs) and explored as the electrocatalyst for methanol oxidation reaction (MOR) for direct methanol fuel cells applications. Highly ordered SiNCs array fabricated using the porous anodic aluminum oxide as the template had a high surface area. Well-dispersed Pt nanopetals possessing high electrocatalytic surface area was synthesized by pulse-electrodeposition on the SiNCs. Pt nanopetals loaded on highly ordered SiNC support exhibited very good catalytic activity for MOR and a high tolerance against CO poisoning, as compared to Pt nanoflowers/flat Si, Pt nanoparticles/flat Si, and many previously reported works. The abundance of a large surface area for facile transport of methanol, SiO(2) sites in the vicinity of the SiNCs, as well as less contact area between the Pt nanopetals catalyst and SiNCs are suggested to be the major factors enhancing the electrocatalytic performance of the Pt nanopetal/SiNC electrode. Moreover, we believe this new nanostructure (Pt nanopetals/SiNCs) will enable many new advances in nanotechnology.
ACS Appl Mater Interfaces 2010 Aug
PMID:Synthesis of Pt nanopetals on highly ordered silicon nanocones for enhanced methanol electrooxidation activity. 2073 93


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