Polymer‐Coated PtCo Nanoparticles Deposited on Diblock Copolymer Templates: Chemical Selectivity versus Topographical Effects

Metal–polymer hybrid films are prepared by deposition of polymer‐coated PtCo nanoparticles onto block copolymer templates. For templating, a thin film of the lamella‐forming diblock copolymer poly(styrene‐b‐methyl methacrylate) P(S‐b‐MMA) is chemically etched and a topographical surface relief with 3 nm height difference is created. Two types of polymer‐grafted PtCo nanoparticles are compared to explore the impact of chemical selectivity versus the topographical effect of the nanotemplate. A preferable wetting of the polystyrene (PS) domains with poly(styrenesulfonate) (PSS)‐coated PtCo nanoparticles (instead of residing in the space between the domains) is observed. Our investigation reveals that the interaction between PSS‐coated nanoparticles and PS domains dominates over the topographical effects of the polymer surface. In contrast, a non‐selective deposition of poly(N‐vinyl‐2‐pyrrolidone) (PVP)‐coated PtCo nanoparticles and the formation of large metal‐particle aggregates on the film is observed.     

Surface-induced breakout crystallization in cylinder-forming P(I-b-EO) diblock copolymer thin films

We have found very slow crystallization in thin films of cylinder-forming poly(isoprene-b -ethyleneoxide) (P(I-b -EO)) diblock copolymers with PEO being the minority block. The film was crystallized at room temperature after melting at 62 ^°C . Imaging methods were combined with X-ray reflectometry and grazing-incidence small-angle X-ray scattering and diffraction. Initially, hexagonally packed, amorphous PEO cylinders lie in the film plane. After 148 days, crystallized, finger-like terraces were observed over the entire film surface. The terrace height is 20% higher than the repeat distance in the as-prepared film. Thus, at the film surface, the cylinders have been destroyed by crystalline lamellae lying in the film plane. The PEO chain stems are perpendicular to the substrate surface and are once-folded and fully interdigitated. The substrate-near layers still consist of the hexagonally packed, amorphous PEO cylinders within the PI matrix.     

Lithium‐Salt‐Containing High‐Molecular‐Weight Polystyrene‐block‐Polyethylene Oxide Block Copolymer Films

Ionic conductivity in relation to the morphology of lithium‐doped high‐molecular‐weight polystyrene‐block‐polyethylene oxide (PS‐b‐PEO) diblock copolymer films was investigated as solid‐state membranes for lithium‐ion batteries. The tendency of the polyethylene (PEO) block to crystallize was highly suppressed by increasing both the salt‐doping level and the temperature. The PEO crystallites completely vanished at a salt‐doping ratio of Li/EO>0.08, at which the PEO segments were hindered from entering the crystalline unit of the PEO chain. A kinetically trapped lamella morphology of PS‐b‐PEO was observed, due to PEO crystallization. The increase in the lamella spacing with increasing salt concentration was attributed to the conformation of the PEO chain rather than the volume contribution of the salt or the previously reported increase in the effective interaction parameter. Upon loading the salt, the PEO chains changed from a compact/highly folded conformation to an amorphous/expanded‐like conformation. The ionic conductivity was enhanced by amorphization of PEO and thereby the mobility of the PEO blocks increased upon increasing the salt‐doping level.     

Layered TiO2 :PVK nano-composite thin films for photovoltaic applications

The influence of the solvent used for spin-coating on the homogeneity of poly(N-vinylcarbazole) (PVK) films is investigated. Homogenous films are obtained only by the use of toluene, solution in tetrahydrofuran (THF) and chloroform results in radially oriented inhomogeneities and films prepared by use of N-methylpyrrolidone and dimethylacetamide show particle formation during spin-coating. Layered nano-composite thin films are prepared by spin-coating a PVK film on top of a nano-structured titanium dioxide ( TiO2) layer. The TiO2 thin films are prepared by a sol-gel process using an amphiphilic copolymer as structure-directing agent. Structural characterisation of the TiO2 :PVK nano-composite films is done by field emission scanning electron microscopy (FESEM) and grazing-incidence small-angle scattering (GISAXS). Bare TiO2 films are probed for comparison. Light is basically only absorbed in the ultraviolet regime and absorption slightly increases upon addition of PVK, which makes the layered TiO2 :PVK nano-composite thin films good candidates for UV photovoltaic devices. Furthermore, absorption remains stable over a period of several days.     

Copper redox behavior, structure and properties of copper lead borate glasses

Copper oxidation states, structure and properties of xCuO · (50-x)PbO · 50B₂O₃ glasses were investigated. Both infrared (IR) and ¹¹B magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies were employed to determine the tetrahedral BO₄ fraction in the glasses as a function of CuO content. IR study indicates that the replacement of Pb²⁺ by Cu²⁺ ions increases the BO₃ units by converting BO₄- containing groups into ring type metaborate groups. The oxidation states of copper ions in the glasses have been studied using both X-ray photoelectron spectroscopy (XPS) and the wet chemical method. For high CuO containing (?30 mol%) glasses, high Cu⁺ ion concentrations (Cu⁺/Cu_tot.>0.3) result in a relatively slow disproportionation of B⁴-containing groups because of the small coordination number of Cu⁺ compared to Cu²⁺ ions. Effects of both glass structure and redox states of copper ions on glass properties including density, Vickers’ hardness, coefficient of thermal expansion, and chemical durability have been discussed.     

Surface characterizations of mono-, di-, and tri-aminosilane treated glass substrates

The surface properties and structure of mono-, di-, and tri-aminosilane treated glass surfaces were investigated using surface analytical techniques including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM), and streaming potential. An optimized dip-coating process was demonstrated to produce roughly silane monolayer coverage on the glass surface. The surface charge measurements indicated that aminosilanization converts the glass surface from negative to positive potentials at neutral pH values. Higher positive streaming potential was observed for tri-compared with mono- and di-aminosilane treated glass surfaces. For all aminosilane treated glass samples, the high-resolution N 1s XPS spectra indicated a preferential orientation of the protonated amino-groups towards the glass surface whereas the free amino groups were protruding outward. This study aimed to obtain uniform, reproducibly thin, strongly adhering, internally cross-linked, and high positively charged aminosilane-coated glass surfaces for the attachment of DNA fragments used in microarraying experiments.     

Properties and structure of copper ultraphosphate glasses

The structures of xCuO · (1 − x)P₂O₅ glasses (0 ? x ? 0.50) prepared in vacuum sealed silica ampoules were investigated using vibrational spectroscopies. With the addition of CuO, both infrared and Raman spectra indicate a systematic transformation from a three-dimensional ultraphosphate network dominated by Q³ tetrahedra into a chain-like metaphosphate structure dominated by Q² tetrahedra. IR spectra clearly show two distinct Q³ sites with bands at 1378 and 1306 cm⁻¹, assigned to PO bonds on isolated Q³ tetrahedra and PO bonds on tetrahedra that participate in the coordination environments of the Cu-octahedra, respectively. As CuO content increases, the intensity of the PO band associated with the tetrahedra increases to a maximum x ∼ 0.33, then decreases with a concomitant increase of the intensity of the band at 1265 cm⁻¹, due to the asymmetric vibration of the PO₂ groups on Q² tetrahedra. When x > 0.33 the isolated Cu-octahedra begin to share common oxygens to form a sub-network in the phosphate matrix. The effects of glass structure on the glass properties, including density, refractive index, and glass transition temperature, are discussed.     

Determination of plastic stress-strain behavior by digital-image-processing techniques

This work explores the application of digitalimage-processing techniques to the measurement of large plastic strains. Two sample problems have been selected, namely the uniform tensile deformation of aluminum-sheet metal strips and the post-necking deformation of copper circular rods. Images of these gridded metallic test pleces were captured, digitized and analyzed in a fully computerized way to evaluate strain distributions, anisotropic parameters and plastic stress-strain flow curves. For post-necked test pieces, Bridgman stress correction has been easily applied by defining the neck profile contour from the automated processing of digitized images. Results compare satisfactorily with those based on displacements measured by conventional microscopy. The presented technique, with added improvements, can consititute a viable one for accurate and fully computerized measurement of large deformations.     

Quantification of terbutaline in pharmaceutical formulation and human serum by adsorptive stripping voltammetry at a glassy carbon electrode

The electrochemical oxidative behavior of terbutaline at the glassy carbon electrode was studied in a series of the Britton-Robinson buffer of pH 2--11. Cyclic and square-wave voltammograms of terbutaline at the pH values 相似文献