bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mask‐free Localized Grafting of Organic Polymers at the Micrometer or Submicrometer Scale on Composite Conductors or Semiconductor Substrates
Authors: Charlier J. , Ameur S. , Bourgoin J. P. , Bureau C. , Palacin S. 
Published: February 2004

AbstractThis work presents a new one‐step process enabling the mask‐free localized functionalization by organic polymers of the conducting or semiconducting parts of composite surfaces at the micrometer and submicrometer scale. The functionalization is carried out via cathodic electrografting of suitable precursors of composite cathodes, which gives an insulating polymer film strongly grafted to selected parts of the composite electrodes and guarantees that the resolution is that of the pre‐existing pattern, even when the whole surface is dipped into the reaction medium. The presumed mechanism is based on a regioselective extraction of electrons from the composite surface according to its apparent local work function in solution.
Spatially Selective Nucleation of Metal Clusters on the Tobacco Mosaic Virus
Authors: Knez M. , Sumser M. , Bittner A. M. , Wege C. , Jeske H. , Martin T. P. , Kern K. 
Published: February 2004

AbstractTobacco mosaic virus (TMV) is a very stable nanotube complex of a helical RNA and 2130 coat proteins. The special shape makes it an interesting nano‐object, especially as a template for chemical reactions. Here we use TMV as a chemically functionalized template for binding metal ions. Different chemical groups of the coat protein can be used as ligands or to electrostatically bind metal ions. Following this activation step, chemical reduction and electroless plating produces metal clusters of several nanometers in diameter. The clusters are attached to the virion without destroying its structure. Gold clusters generated from an ascorbic acid bath bind to the exterior surface as well as to the central channel of the hollow tube. Very high selectivity is reached by tuning PdII and PtII activations with phosphate: When TMV is first activated with PdII, and thereafter metallized with a nickel–phosphinate bath, 3 nm nickel clusters grow in the central channel; when TMV from phosphate‐buffered suspensions is employed, larger nickel clusters grow on the exterior surface. Phosphate buffers have to be avoided when 3 nm nickel and cobalt wires of several 100 nm in length are synthesized from borane‐based baths inside the TMV channel. The results are discussed with respect to the inorganic complex chemistry of precursor molecules and the distribution of binding sites in TMV.
Build‐up of Polypeptide Multilayer Coatings with Anti‐Inflammatory Properties Based on the Embedding of Piroxicam–Cyclodextrin Complexes
Authors: Benkirane‐Jessel N. , Schwinté P. , Falvey P. , Darcy R. , Haïkel Y. , Schaaf P. , Voegel J.‐C. , Ogier J. 
Published: February 2004

AbstractWe describe the build‐up of biomaterial coatings based on polypeptide multilayers possessing anti‐inflammatory properties. Poly(L‐lysine) (PLL) and poly(L‐glutamic acid) (PGA) are used as polypeptides, and piroxicam (Px) is used as the anti‐inflammatory agent. In order to embed high enough amounts of Px, the drug is incorporated in the films in the form of complexes with a charged 6A‐carboxymethylthio‐β‐cyclodextrin (cCD). It is shown that this cyclodextrin can solubilize higher amounts of Px than the cyclodextrins used commercially. The anti‐inflammatory properties are evaluated by determining the inhibition of TNFα production by human monocytic THP‐1 cells stimulated with lipopolysaccharide (LPS) bacterial endotoxin. Using Fourier‐transform (FT) Raman spectroscopy, we show that Px is mainly in the neutral form in cCD–Px complexes in solution, and that it remains biologically active under this form, whereas up to now only the zwitterionic form was reported to possess anti‐inflammatory properties. When incorporated in PLL/PGA multilayers, Px in the cCD–Px complexes changes from the neutral to the zwitterionic form. It is shown that these films present anti‐inflammatory properties, which can be delayed, and whose duration can be tuned by changing the film architecture.
A Simple and Effective Route for the Synthesis of Crystalline Silver Nanorods and Nanowires
Authors: Hu J.‐Q. , Chen Q. , Xie Z.‐X. , Han G.‐B. , Wang R.‐H. , Ren B. , Zhang Y. , Yang Z.‐L. , Tian Z.‐Q. 
Published: February 2004

AbstractA simple and effective approach to the aqueous‐phase synthesis of crystalline silver nanorods and nanowires is demonstrated, using which their diameters and aspect ratios can be effectively controlled. The synthesis involves a template‐less and non‐seed process to high‐quality nanoparticles, which is low‐cost and proceeds at moderate temperatures. The nanorods and nanowires were synthesized by the reduction of silver nitrate with tri‐sodium citrate in the presence of sodium dodecylsulfonate. The concentration of tri‐sodium citrate plays a critical role while sodium dodecylsulfonate, as a capping agent, only plays an assistant role in controlling the diameters and aspect ratios of the products. High‐resolution transmission electron microscopy (HRTEM) and selected‐area electron diffraction (SAED) investigations show that the silver nanocrystals are generated with a twinned crystalline structure. We also put forward a primary experimental model to shed light on their growth mechanisms.
Alizarin Complexone on Nanocrystalline TiO2: A Heterogeneous Approach to Anion Sensing
Authors: Palomares E. , Vilar R. , Green A. , Durrant J. R. 
Published: February 2004

AbstractA novel, heterogeneous approach to “naked‐eye” colorimetric and spectrophotometric anion sensing is demonstrated, employing the molecular receptor alizarin complexone adsorbed onto a nanocrystalline, mesoporous TiO2 film. pH buffer action intrinsic to the TiO2 film allows dip sensing in aqueous solutions. This heterogeneous sensing system exhibits a high selectivity to F– and CN– anions, high sensitivity, a rapid response time, and excellent reusability.
Columnar Liquid Crystals with a Central Crown Ether Unit
Authors: Schultz A. , Laschat S. , Saipa A. , Gießelmann F. , Nimtz M. , Schulte J. L. , Baro A. , Miehlich B. 
Published: February 2004

AbstractNovel columnar liquid crystals 5a–f bearing a dibenzo[18]crown[6] central unit have been prepared from bromodialkyloxybenzenes 1 and tetrabromodibenzo[18]crown[6] 2 via Suzuki coupling reactions. Differential scanning calorimetry (DSC) revealed that the length of the alkyl chains in the liquid‐crystalline compounds 5 influenced their mesomorphic properties. Whereas 5a–d gave fan‐shaped textures only upon rapid cooling, 5e and 5f with C9 and C10 side chains formed stable columnar textures upon slow cooling. A hexagonal columnar mesophase of 5a is apparent from X‐ray diffraction studies. Complexation of 5 with potassium significantly shifted the clearing points to higher temperatures and also increased the mesophase stability in the cooling cycle.
Conducting‐Polymer Microcontainers: Controlled Syntheses and Potential Applications
Authors: Bajpai V. , He P. , Dai L. 
Published: February 2004

AbstractWe have demonstrated the controlled synthesis of conducting‐polymer microcontainers through the electrochemical generation of surfactant (i.e., β‐naphthalenesulfonic acid, β‐NSA)‐stabilized H2 gas bubbles on the working electrode, followed by electrochemical polymerization of pyrrole around the wall of the “soap‐bubble” template. It was noticed that the density, shape, and wall thickness of the polypyrrole microcontainers thus prepared could be regulated by controlling the electrochemical potential applied for the generation of H2 gas and the experimental conditions (e.g., the surfactant concentration, number of the cyclic voltammetric scanning) for the electropolymerization of pyrrole. By pre‐patterning the working electrode surface with non‐conducting polymers using microcontact printing (μCP) or plasma patterning, we have also produced conducting‐polymer microcontainers in a patterned fashion. Furthermore, potential applications of the patterned and non‐patterned conducting‐polymer microcontainers have been demonstrated; for example, through the encapsulation of appropriate fluorescence‐labeled molecules (e.g., fluorescein cadaverin) into the conducting‐polymer microcontainers by sealing their opened mouths with sequential electropolymerization of pyrrole. The resulting closed microcontainers could then be used for controlled releases.
On the Feasibility of Growing Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 Single Crystals
Authors: Fang B.‐J. , Shan Y.‐J. , Xu H.‐Q. , Luo H.‐S. , Yin Z.‐W. 
Published: February 2004

AbstractPb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/9) single crystals were grown by two methods: from solution using PbO as a self‐fluxing agent (SC method) and directly from the melt without fluxing (MC method). In both growth methods, an allomeric Pb[(Mg1/3‐Nb2/3)0.69Ti0.31]O3 (PMNT69/31) single crystal was used as a seed. X‐ray diffraction patterns of ground crystals showed that phase‐pure perovskite PZNT91/9 single crystals were successfully fabricated by the above two methods. The composition of the crystals obtained by both the SC and MC methods was analyzed using X‐ray fluorescence, which confirmed that the crystal composition is close to the nominal value, although volatilization of PbO and segregation during crystal growth are inevitable. The MC PZNT91/9 crystals exhibit excellent piezoelectric properties, with the piezoelectric constant, d33, in the range of 1800–2200 pC N–1. This value is comparable to that of the SC crystals. However, the MC crystals show an abnormal dielectric behavior. In contrast with the SC crystals, in the MC crystals a much broader dielectric peak appears in the dielectric response curves, accompanied by a much lower peak temperature of around 105 °C. Furthermore, frequency dispersion is apparent over a much wider temperature range (even more apparent than in pure relaxors), where a large, i.e., about 70 °C, full width at half maximum (FWHM) for the dielectric peaks is observed in the dielectric response. It is speculated that such an unusual phenomenon correlates with defects, microinhomogeneities, and polar regions in the as‐grown MC crystals. The origins of this abnormality have not been interpreted in detail until now. However, optical observation of the domain structure confirms that both the SC and MC crystals possess complex structural states.
Properties of Carbon Nanotube Fibers Spun from DNA‐Stabilized Dispersions
Authors: Barisci J. N. , Tahhan M. , Wallace G. G. , Badaire S. , Vaugien T. , Maugey M. , Poulin P. 
Published: February 2004

AbstractThe fabrication of single‐walled carbon nanotube (CNT) fibers containing (salmon) DNA has been demonstrated. The DNA material has been found to be adequate for dispersing relatively large concentrations (up to 1 % by weight) of carbon nanotubes. These dispersions are better suited for fiber spinning than previously studied dispersions based on conventional surfactants, such as sodium dodecyl sulfate (SDS). The DNA‐containing fibers were less conductive than the fibers based on SDS, but they were significantly stronger. Considerably increased conductivity was obtained by thermally annealing the CNT/DNA fibers, a process accompanied by a loss in mechanical strength. Smaller improvements in conductivity could be introduced by annealing the carbon nanotubes before fiber production, with no alteration of the fiber mechanical properties. Those CNT/DNA fibers that were mechanically strong and conductive also exhibited good electrochemical behavior and useful capacitance values (up to 7.2 F g–1).
Efficient and Photostable ZnS‐Passivated CdS:Mn Luminescent Nanocrystals
Authors: Yang H. , Holloway P. H. 
Published: February 2004

AbstractEfficient and photostable ZnS‐passivated CdS:Mn (CdS:Mn/ZnS core/shell) nanocrystals were synthesized using reverse micelle chemistry. CdS:Mn/ZnS core/shell nanocrystals exhibited much improved luminescent properties (quantum yield and photostability) over organically (n‐dodecanethiol‐) capped CdS:Mn nanocrystals. This is the result of effective, robust passivation of CdS surface states by the ZnS shell and consequent suppression of non‐radiative recombination transitions. The dependence of photoluminescence (PL) intensity has been observed as a function of UV irradiation time for both organically and inorganically capped CdS:Mn nanocrystals. Whereas organically capped CdS:Mn nanocrystals exhibit a significant reduction of PL intensity, CdS:Mn/ZnS core/shell nanocrystals exhibit an increased PL intensity with UV irradiation. XPS (X‐ray photoelectron spectroscopy) studies reveal that UV irradiation of CdS:Mn/ZnS nanocrystals in air atmosphere induces the photo‐oxidation of the ZnS shell surface, leading to the formation of ZnSO4. This photo‐oxidation product is presumably responsible for the enhanced PL emission, serving as a passivating layer.
Selective Atmospheric Pressure Chemical Vapor Deposition Route to CdS Arrays, Nanowires, and Nanocombs
Authors: Ge J. P. , Li Y. D. 
Published: February 2004

AbstractCdS arrays, nanowires, and nanocombs were selectively prepared through an atmospheric pressure chemical vapor deposition (APCVD) process with CdCl2 and S as sources. The morphologies could be controlled by adjusting the deposition position, the temperature, and the flux of the carrier gas. The phase structure, morphologies, and photoluminescence properties of the CdS products were investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra. The formation mechanism of the nanowires is discussed on the basis of the experimental results. The adopted synthetic route is expected to be applied in the synthesis of other metal sulfide one‐dimensional (1D) nanostructures.
Loading Fullerene into a Conjugated Polymer Without Chemical Modification
Authors: Tada K. , Onoda M. 
Published: February 2004

AbstractConjugated polymers doped with fullerenes show excellent photoconversion efficiencies. However, due to the poor solubility of pure C60 in common organic solvents, it was thought that some chemical modifications to C60 were required in order to load conjugated polymers with comparable weights of fullerene. Here, we report a novel way to load large amounts of unmodified C60 fullerene into the conjugated polymer poly(2‐methoxy‐5‐(2′‐ethylhexoxy)‐1,4‐phenylenevinylene), MEH‐PPV. The principle of our approach is to separate the film‐deposition stage from the material‐solidification stage. That is, materials are quickly solidified from dilute solution into colloidal particles, which are large enough to be collected by electrophoretic deposition. Deposition from a mixture of separate suspensions of MEH‐PPV and C60 fullerene resulted in films consisting of isolated particles. In contrast, by using a suspension made of a dilute solution of MEH‐PPV and C60, which was so dilute that traditional techniques such as spin‐coating were not applicable, an MEH‐PPV film doped with 20 mol‐% C60, corresponding to an almost 1:1 ratio by weight of molecularly dispersed C60, was easily obtained. To the best of our knowledge, this is the first report on the successful loading of an equivalent weight ratio of unmodified C60 molecules into MEH‐PPV.
Inkjet Printing of Polymers: State of the Art and Future Developments
Authors: de Gans B.‐J. , Duineveld P. C. , Schubert U. S. 
Published: February 2004

AbstractInkjet printing is considered to be a key technology in the field of defined polymer deposition. This article provides an introduction to inkjet printing technology and a short overview of the available instrumentation. Examples of polymer inkjet printing are given, including the manufacturing of multicolor polymer light‐emitting diode displays, polymer electronics, three‐dimensional printing, and oral dosage forms for controlled drug release. Special emphasis is placed upon the utilized polymers and conditions, such as polymer structure, molar mass, solvents, and concentration. Studies on viscoelastic fluid jets and the formation of viscoelastic droplets under gravity indicate that strain hardening is the key parameter that determines the inkjet printability of polymer solutions.
Free Radical‐Mediated Acylation and Carboxylation Reactions
Authors: Kim Sunggak 
Published: February 2004

AbstractRadical acylations to prepare carbonyl compounds are described and focus on indirect acylation approaches using sulfonyl oxime ethers under tin‐mediated and tin‐free conditions. The efficiency of carboxylic acid derivatives as carbonyl group radical acceptors in radical acylation and carboxylation reactions is discussed.
Achiral Dihydroxylation of Olefins by Osmate (OsO42−) Stabilised on Nanocrystalline Magnesium Oxide
Authors: Choudary Boyapati M. , Jyothi Karangula , Kantam Mannepalli L. , Sreedhar B. 
Published: February 2004

AbstractA recoverable and reusable new heterogeneous AP‐Mg‐OsO4 catalyst was designed and developed for the first time via a counterionic stabilisation of OsO42− with Mg2+ present on the corner or edge of nanocrystalline MgO. AP‐Mg‐OsO4 catalysed the dihydroxylation of olefins to afford diols with excellent yields in the presence of N‐methylmorpholine N‐oxide for the first time. The absence of osmium and no progress of the dihydroxylation reaction with the filtrate samples withdrawn periodically during the reaction rule out the leaching of osmium unambiguously and provide evidence for the heterogeneity of the reaction. Identification of surface intermediate species by XPS and TGA‐DTA‐mass thermography gives an insight into the mechanism of the dihydroxylation reaction.
Rhodium Acetate Dimer Immobilized in 1‐Butyl‐3‐methylimidazolium Hexafluorophosphate Ionic Liquid: a Novel and Recyclable Catalytic System for the Cyclopropanation of Alkenes
Authors: Yadav J. S. , Reddy B. V. S. , Reddy P. Narayana 
Published: February 2004

AbstractAlkenes undergo smooth cyclopropanation with ethyl diazoacetate using a catalytic amount of rhodium acetate dimer, Rh2(OAc)4, immobilized in the air‐ and moisture‐stable 1‐butyl‐3‐methylimidazolium hexafluorophosphate ionic liquid, [bmim]PF6, to afford cyclopropanecarboxylates in excellent yields with high trans‐selectivity. The recovery of the catalyst is facilitated by the hydrophobic nature of [bmim]PF6. The recovered ionic liquid containing Rh2(OAc)4 can be reused for three to five subsequent runs with only a gradual decrease in activity.
Phosphorus Acids as Highly Efficient Promoters for the Palladium‐Phenanthroline Catalyzed Carbonylation of Nitrobenzene to Methyl Phenylcarbamate†
Authors: Ragaini Fabio , Gasperini Michela , Cenini Sergio 
Published: February 2004

AbstractA new family of promoters, based on phosphorus acids, is reported for the catalytic carbonylation of nitrobenzene to methyl phenylcarbamate by palladium‐phenanthroline complexes. With the new promoters, unprecedented reaction rates (TOF up to 6000/h) and catalyst stability (TON up to 105) could be reached. The best promoter is phosphoric acid, which is also very cheap, nontoxic and easily separable from the reaction products.
Enantioselective Hydrogenation of β‐Acylamino Acrylates Catalyzed by Rhodium(I)‐Monophosphite Complexes
Authors: Jerphagnon Thomas , Renaud Jean‐Luc , Demonchaux Patrice , Ferreira Amadéo , Bruneau Christian 
Published: February 2004

AbstractChiral rhodium(I) complexes bearing monophosphite ligands, prepared from chiral Binol and (L)‐menthol, were found to be efficient catalysts for the asymmetric hydrogenation of β‐acylamino acrylates with ee values up to 94%.
Efficient Synthesis of β,γ‐Alkynyl α‐Amino Acid Derivatives by Ag(I)‐Catalyzed Alkynylation of α‐Imino Esters
Authors: Ji Jian‐Xin , Au‐Yeung Terry T.‐L. , Wu Jing , Yip Chiu Wing , Chan Albert S. C. 
Published: February 2004

AbstractThe first catalytic synthesis of β,γ‐alkynyl α‐amino acid derivatives was achieved by direct addition of terminal alkynes to α‐imino esters in the presence of an Ag(I) salt under mild reaction conditions.
Cyclodextrins or Calixarenes: What is the Best Mass Transfer Promoter for Suzuki Cross‐Coupling Reactions in Water?
Authors: Hapiot F. , Lyskawa J. , Bricout H. , Tilloy S. , Monflier E. 
Published: February 2004

AbstractCyclodextrins or calixarenes possessing extended hydrophobic host cavities and surface‐active properties were found to be very efficient as mass transfer promoters for the palladium‐mediated Suzuki cross‐coupling reaction of 1‐iodo‐4‐phenylbenzene and phenylboronic acid in aqueous medium. The cross‐coupling rates were up to 92 times higher than those obtained without addition of any compound.
Mechanistic Aspects of Formation of Chiral Ruthenium Hydride Complexes from 16‐Electron Ruthenium Amide Complexes and Formic Acid: Facile Reversible Decarboxylation and Carboxylation
Authors: Koike Takashi , Ikariya Takao 
Published: February 2004

AbstractThe 16‐electron amide complex, Ru[(R,R)‐TsNCHPhCHPhNH](η6‐p‐cymene) (Ts=p‐toluenesulfonyl, Ph=C6H5) readily reacts with formic acid to give the corresponding formate complex, which subsequently undergoes decarboxylation leading to the hydride complex with release of CO2. The reaction of this hydride complex with CO2 under mild reaction conditions, a pressure of 10 atm and even at −78 °C, proceeds rapidly to give the corresponding formate complex almost quantitatively. Thus, the reversible decarboxylation and carboxylation takes place with or without the aid of a metal‐NH bifunctional effect of the Ru complexes.
Surfactant‐Stabilized Aqueous Iridium(0) Colloidal Suspension: An Efficient Reusable Catalyst for Hydrogenation of Arenes in Biphasic Media
Authors: Mévellec Vincent , Roucoux Alain , Ramirez Esther , Philippot Karine , Chaudret Bruno 
Published: February 2004

AbstractAqueous suspensions of iridium nanoparticles produced by the chemical reduction of IrCl3 assisted by sonication, in the presence of N,N‐dimethyl‐N‐cetyl‐N‐(2‐hydroxyethyl)ammonium chloride salt as surfactant, have shown an efficient activity for the catalytic hydrogenation of various aromatic derivatives in biphasic media under mild conditions. These nanocatalysts can be reused for further runs with a total conservation of activity and provided significant catalytic lifetime for anisole hydrogenation in pure water with 3000 total turn‐over (TTO).
Recycling Chiral Imidazolidin‐4‐one Catalyst for Asymmetric Diels–Alder Reactions: Screening of Various Ionic Liquids
Authors: Park Jin Kyoon , Sreekanth Pentlavalli , Kim B. Moon 
Published: February 2004

AbstractVarious imidazolium ionic liquids such as [Bmim]PF6, [Bmim]SbF6, [Bmim]OTf and [Bmim]BF4 were screened for recycling an organic catalyst [(5S)‐5‐benzyl‐2,2,3‐trimethylimidazolidin‐4‐one (1)] for asymmetric Diels–Alder reactions. Good yields and enantioselectivies (up to 85% yield and 93% ee) were obtained from reactions in [Bmim]PF6 or [Bmim]SbF6. However, reactions in [Bmim]OTf or [Bmim]BF4 gave racemic products in low yields. Isolation of the products by simple extraction using diethyl ether allowed recycling of the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.