Controlling Interfacial Ion-Transport Kinetics Using Polyelectrolyte Membranes for Additive- and Effluent-free, High-Performance Electrodeposition.

The development of high-performance, environmentally friendly electrodeposition processes is critical for emerging coating technologies because current technologies use highly complex baths containing metal salts, supporting electrolytes, and various kinds of organic additives, which are problematic from both environmental and cost perspectives. Here, we show that a 200 μm-thin polyelectrolyte membrane sandwiched between electrodes effectively concentrates metal ions through interfacial penetration, which increases the conductance between the electrodes to 0.30 S and realizes solid-state electrodeposition that produces no mist, sludge, or even waste effluent.

Preparation of Ni nanoparticles by liquid-phase reduction to fabricate metal nanoparticle-polyimide composite films.

Nickel-nanoparticle-containing polyimide composite films were prepared by liquid-phase reduction of Ni ions with potassium borohydride (KBH). The nanoparticles were amorphous with diameters of approximately 10-20 nm, depending on the KBH concentration and reduction temperature. At high KBH concentrations, the nanoparticles appeared to contain various nickel boride species.

Metal nanocrystal/metal-organic framework core/shell nanostructure from selective self-assembly induced by localization of metal ion precursors on nanocrystal surface.

Metal nanocrystal/metal-organic framework core/shell nanostructures have been constructed using metal ion-trapped nanocrystals as scaffolds through a selective self-assembly of framework components on the nanocrystal surfaces. The resulting nanostructures exhibit unique catalytic activity toward nitrophenol analogs.

A facile template synthesis of asymmetric gold silica heteronanoparticles.

Silica hemispheres containing gold nanoparticle cores have been synthesized via immobilization of gold nanoparticles on a substrate and site-selective growth of silica followed by removal of the hemispherical particles. The structure of these asymmetric heteronanoparticles allows selective etching or overgrowth of the core gold seeds, which results in the respective formation of hemispherical capsules or gold homodimers.

Controlled self-assembly of metal-organic frameworks on metal nanoparticles for efficient synthesis of hybrid nanostructures.

We report a novel approach for synthesizing inorganic nanoparticle/metal-organic frameworks (MOFs) heterostructured nanocomposites by self-assembly of MOFs on nanoparticles. This approach involves the synthesis of Au nanoparticles and preferential growth of [Cu(3)(btc)(2)](n) frameworks consisting of Cu(2+) ions and benzene-1,3,5-tricarboxylate (btc) on nanoparticles. Aggregates consisting of 11-mercaptoundecanoic acid (MUA)-stabilized Au nanoparticles linked by Cu(2+) ions were necessary for preferential self-assembly of [Cu(3)(btc)(2)](n) frameworks on the aggregates, resulting in the formation of Au nanoparticles/[Cu(3)(btc)(2)](n) nanocomposites.

Fabrication of silver patterns on polyimide films based on solid-phase electrochemical constructive lithography using ion-exchangeable precursor layers.

We report a fully additive-based electrochemical approach to the site-selective deposition of silver on a polyimide substrate. Using a cathode coated with ion-doped precursor polyimide layers, patterns of metal masks used as anodes were successfully reproduced at the cathode-precursor interface through electrochemical and ion-exchange reactions, which resulted in the generation of silver patterns on the polyimide films after subsequent annealing and removal from the substrate. Excellent interfacial adhesion was achieved through metal nanostructures consisting of interconnecting silver nanoparticles at the metal-polymer interface, which are electrochemically grown "in" the precursor layer.

Fabrication of copper damascene patterns on polyimide using direct metallization on trench templates generated by imprint lithography.

Facile imprint and wet chemical processes were used to fabricate copper damascene patterns on polyimide substrate. Poly(amic acid) substrate with trench structures as template has been successfully prepared by imprint lithography using a poly(dimethylsiloxane) mold. The doped Ni(2+) ions into a template through ion-exchange reaction were reduced by an aqueous NaBH(4) solution, resulting in the formation of a nickel thin layer along the surface structure of the template.

Synthesis and characterization of polypyrrole-palladium nanocomposite-coated latex particles and their use as a catalyst for Suzuki coupling reaction in aqueous media.

Polypyrrole-palladium (PPy-Pd) nanocomposite was deposited in situ from aqueous solution onto micrometer-sized polystyrene (PS) latex particles. The PS seed particles and resulting composite particles were extensively characterized with respect to particle size and size distribution, morphology, surface/bulk chemical compositions, and conductivity. PPy-Pd nanocomposite loading onto the PS seed latex particles was systematically controlled over a wide range (10-60 wt %) by changing the weight ratio of the PS latex and PPy-Pd nanocomposite.

Synthesis of pH-responsive nanocomposite microgels with size-controlled gold nanoparticles from ion-doped, lightly cross-linked poly(vinylpyridine).

The synthesis of composite microgels consisting of pH-responsive latexes with gold nanoparticles was investigated along with the optical properties of the products. The gold nanoparticles were deposited by wet chemical reduction from gold ions adsorbed in cross-linked poly(2-vinylpyridine) latexes, by which the mean particle size of the gold nanoparticles could be systematically controlled over a range of 10-30 nm simply by varying the reduction rate. Microscopic analysis showed that the gold nanoparticles were formed only on the surface of the microgels, resulting from diffusion of the gold ions from the interior to the surface of the microgels during reduction treatment.

Molecularly imprinted nanocomposites for highly sensitive SPR detection of a non-aqueous atrazine sample.

A surface plasmon resonance (SPR) sensor highly sensitive and selective for the herbicide atrazine was composed by immobilizing atrazine-imprinted polymer with gold nanoparticles on a gold thin film as a sensor chip. In the detection, the atrazine-imprinted polymer was expected to work as synthetic receptor for selectively capturing atrazine in organic solvent, and the gold nanoparticles were expected to exhibit a coupling effect with the gold thin film to enhance the local electromagnetic field between the nanoparticles and the gold film, making the sensor chip highly sensitive for changes in microenvironmental polarity. Thus, a combination of the atrazine-imprinted polymer and gold nanoparticles enabled us to compose an SPR sensor demonstrating the detection of 5 pM atrazine in acetonitrile.

Control of the optical properties of CdTe nanocrystals by selective exchange of Te with thiolate: effect of organic ligands on the formation of core-shell structures.

Changes in the optical properties of CdTe nanocrystals through selective surface exchange reaction with thiolate molecules in the organic phase are studied with an aim to investigate the mechanism and the role of organic ligands. The reaction was mediated by dissociation of Te anions via oxidation in air from CdTe nanocrystals, followed by attachment of thiolate molecules in a 1:1 stoichiometric manner. This results in a gradual shell formation and a corresponding decrease in the size of the fluorescent CdTe cores, which induces a blue shift of both the absorption edge and emission wavelength in the visible region.

Highly luminescent mono- and multilayers of immobilized CdTe nanocrystals: controlling optical properties through post chemical surface modification.

The significant fluorescence enhancement of immobilized CdTe nanocrystals through chemical surface modifications is described, enabling us to fabricate stable, highly luminescent thin films and patterns of nanocrystal mono- and mutilayers.

Atomic beam-induced fluorination of polyimide and its application to site-selective Cu metallization.

Metallization methods of polyimide by hyperthermal atomic oxygen and atomic fluorine beams were developed. An atomic fluorine beam with a translational energy of 6.2 eV modified the wettability of polyimide surfaces to provide an advancing water contact angle of 132 degrees.

A DNA duplex with extremely enhanced thermal stability based on controlled immobilization on gold nanoparticles.

The effect of DNA loadings on the thermal stability of DNA duplex immobilized on gold nanoparticles has been investigated. The modestly loaded duplexes on the gold nanoparticles showed enhanced thermal stability, as compared to that of the free duplex (without gold nanoparticles). However, the highly loaded duplex showed stability similar to that of free duplex.

Site-selective direct photochemical deposition of copper on glass substrates using TiO2 nanocrystals.

Deposition of copper thin films was achieved by a photocatalytic reaction of site-selectively adsorbed TiO(2) nanocrystals for direct fabrication of copper circuit patterns on glass substrates. The nanocrystal monolayers absorbed on hydrophobic surface templates serve as an effective photocatalyst, producing metallic copper and formic acid via oxidation of methanol in solution. The formic acid generated has also been suggested to serve as an electron donor that accelerates copper deposition through a UV-mediated autocatalytic reaction, even after nanocrystals are embedded into the grown copper films.

SPR sensor chip for detection of small molecules using molecularly imprinted polymer with embedded gold nanoparticles.

Molecularly imprinted polymer gel with embedded gold nanoparticle was prepared on a gold substrate of a chip for a surface plasmon resonance (SPR) sensor for fabricating an SPR sensor sensitive to a low molecular weight analyte. The sensing is based on swelling of the imprinted polymer gel that is triggered by an analyte binding event within the polymer gel. The swelling causes greater distance between the gold nanoparticles and substrate, shifting a dip of an SPR curve to a higher SPR angle.

Controlling interparticle spacing among metal nanoparticles through metal-catalyzed decomposition of surrounding polymer matrix.

Systematic and reproducible control over average interparticle spacing of Pt, Ni, and Cu nanoparticles embedded in polyimide thin layers was achieved. The metal-catalyzed decomposition of polyimide matrixes surrounding metal nanoparticles causes a decrease in the composite layer thickness, while maintaining the size of nanoparticles. This ability provides an effective methodology for the preparation of metal/polymer nanocomposites with tailored microstructures and holds great promise toward the fundamental understanding of the physical interactions among metal nanoparticles.

Stereocontrolled synthesis and optical properties of all-cis poly(phenylene vinylenes) (PPVs): a method for direct patterning of PPVs.

Geometrically pure, all-cis poly(phenylene vinylenes) (PPVs) are synthesized by Suzuki-Miyaura-type polycondensation of 2,5-dioctyloxy-1,4-benzenediboronic acid with (Z,Z)-bis(2-bromoethenyl)benzenes, which are prepared by ruthenium-catalyzed (Z)-selective double hydrosilylation of diethynylbenzenes, followed by bromodesilylation of the resulting (Z,Z)-bis(2-silylethenyl)benzenes with N-bromosuccinimide. The all-cis PPVs thus obtained undergo one-way photoisomerization to the corresponding trans-PPVs both in solution and in the solid. This phenomenon is applied to direct microscale patterning of PPVs onto a quartz substrate.

Band gap engineering of CdTe nanocrystals through chemical surface modification.

We demonstrate band gap control of CdTe nanocrystals by selective surface modification using alkanethiol molecules. Both absorption and emission wavelengths can be tuned simply by mixing a dispersion of the nanocrystals with alkanethiol at room temperature, resulting in blue shifts in the optical spectra during reaction. The degree of blue shift depends on both the concentration of alkanethiols and the reaction time, thereby providing kinetic control over the emission peak wavelength of the nanocrystals in mild conditions.

Synthesis, surface modification, and multilayer construction of mixed-monolayer-protected CdS nanoparticles.

Herein, we describe a study aimed at synthesizing mixed-monolayer-protected CdS nanoparticles and investigating the reactivity of surface-bound functional groups in order to facilitate the immobilization of nanoparticles on a solid substrate as well as the construction of a three-dimensional nanocomposite. CdS nanoparticles initially prepared by the reverse micelle method were used to modify nanoparticle surfaces with 1-decanethiol molecules by ligand exchange. Subsequently, 11-mercapto-1-undecanol was partially incorporated by a place exchange reaction, thereby providing stable, mixed-monolayer-protected CdS nanoparticles.

Direct patterning of copper on polyimide using ion exchangeable surface templates generated by site-selective surface modification.

We demonstrate site-selective chemical surface modification by dispensing potassium hydroxide solution onto polyimide, which confines source metallic ions that can subsequently be used in resist- and mask-free fabrication of copper circuit patterns. Metallization can be achieved by a wet chemical method, providing control over metal/polymer interfacial structures. Because the approach is compatible with other existing printing technologies and much simpler than conventional lithography-based methods, we propose that the present surface template method may be of general application in fabrication of metallized polymers as well as in development of integrated circuits with a variety of electronic circuit elements.

Composite of Au nanoparticles and molecularly imprinted polymer as a sensing material.

A molecularly imprinted polymer with immobilized Au nanoparticles (Au-MIP) is reported as a novel type of sensing material. The sensing mechanism is based upon the variable proximity of the Au nanoparticles immobilized in the imprinted polymer, which exhibits selective binding of a given analyte accompanied by swelling that causes a blue-shift in the plasmon absorption band of the immobilized Au nanoparticles. Using adrenaline as the model analyte, it was shown that molecular imprinting effectively enhanced the sensitivity and selectivity, and accordingly, Au-MIP selectively detects the analyte at 5 microM.