Materials Literature
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Without large investments in new clean-room facilities, the nano- and microstructures described here can be achieved by the combination of wet-chemistry with existing conventional lithographic techniques. One of the advantages of the method is that it allows the specific formation of aperiodic patterns, which are of s…
The reaction of Zr(OR)4 (OR = OnBu, OnPr) with methacrylic acid was monitored by extended X-ray absorption fine structure (EXAFS), 1H and 13C NMR, HPLC, and Raman measurements. The study revealed that the initial dimeric zirconium alkoxides react rapidly with the carboxylic acid and form higher aggregated multinuclear…
Enhanced photocurrents are detected in the presence of bipyridinium-modified CdS nanoparticles associated with electrodes. The enhanced photocurrents originate from vectorial electron transfer that retards recombination processes. The Figure shows different architectures for CdS nanoparticles on Au electrodes.
Moieties that can be cross-linked appear to be the necessary feature of dendrimers that can be used to make poled polymers displaying high chromophore density, excellent electrooptic properties, and good thermal and temporal stability. Such materials could find use in optical telecommunications and public networking.
Highly ordered boron nanowire multiple nanojunctions (see Figure) with unilateral feather-like morphology have been created via a simple magnetron sputtering method. These T- and Y-type nanojunctions stand freely in line to form uniform and well-oriented arrays on the substrate surface over areas of up to several tens…
A series of chiral phosphine-functionalized poly(propyleneimine) (PPI) dendrimers was synthesized by the reaction of carboxyl-linked C(2)-chiral pyrphos ligand (pyrphos=3,4-bis(diphenylphosphino)pyrrolidine) with zeroth-fourth generation PPI using ethyl-N,N-dimethylaminopropylcarbodiimide (EDC)/1-hydroxybenzotriazol a…
The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall, the studies show that the re…
One-step simultaneous immobilization of two enzymes, horseradish peroxidase (HRP) and glucose oxidase (GOx), was achieved in mesoporous materials. β-D-Glucose was the substrate of GOx to yield H2O2, which became the substrate of the second enzyme, HRP. The mesoporous biogels showed two to three orders of magnitude fas…
A general force field methodology is developed for description of molecular interactions in carbon-based materials. The method makes use of existing parameters of potential functions developed for sp(2) and sp(3) carbons and allows accurate representation of molecular forces in curved carbon environment. The potential…
A new technique of metal nanopowder production and in situ coating using a microarc discharge is proposed. The feasibility of this method is demonstrated and preliminary results are presented. The microarc discharge was operated at 1 atm in both pure Ar and natural gas environments. Respectively, aluminium nanoparticl…
It was proposed that nanoparticles of layered compounds are not stable in the planar form and they spontaneously fold into fullerene-like structures and nanotubes (IF phases). Considering the spherical topology of the IF nanoparticles, it was proposed that they could ideally suit tribological applications. In this pap…
Dielectric relaxation spectroscopy (1 Hz - 20 GHz) has been performed on supercooled glass-formers from the temperature of glass transition (T(g)) up to that of melting. Precise measurements particularly in the frequencies of MHz order have revealed that the temperature dependences of secondary beta relaxation times i…
Evaporation-driven surface templating by means of a vibrating orifice aerosol generator (VOAG), a device that produces microdroplets, has been used for the synthesis of non-hollow monodisperse mesoporous silica particles (see Figure for a TEM image). Particle and pore size as well as mesoscopic order are controllable…
“Smart dust”—small particles of optically encoded microporous Si—can detect organic vapors by measurement of the intensity of reflected light using a laser probe and a detector stationed 20 m away (see Figure and inside front cover). The porous particles absorb condensable vapors, producing a change in refractive inde…
The phase change from a charge- and orbital-ordered insulator to a ferromagnetic metal has been investigated for single crystals of ${\mathrm{Pr}}_{0.55}({\mathrm{Ca}}_{1\ensuremath{-}y}{\mathrm{Sr}}_{y}{)}_{0.45}{\mathrm{MnO}}_{3}$ with controlled one-electron bandwidth. At $0<~y<~0.2,$ the ground state is the…
Physical stabilization of triphenylene-based charge-transfer complexes by hexagonally aligned silica channels enables the preparation of color-tunable, highly transparent mesoporous silica films (see picture). The donor/acceptor molar ratio was varied over a wide range (1:1 to 9:1) with the included charge-transfer co…
Liquid crystallinity of layered niobate K4Nb6O17 colloidally dispersed via exfoliation has been achieved as evidenced by birefringence of the colloid (see Figure). Due to the large lateral size of the nanosheets, the liquid-crystalline state is stable down to low concentrations and macroscopic alignment is easily indu…
For the first time, silica nanofibres with diameters of 200–400 nm were prepared by using electrospun fibres of polyvinylalcohol/silica composite as precursor. The products were characterized by the scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and x-ray diffractometry (XRD) meth…
Thermal decomposition of the respective trisulfides in a reducing (H2/inert gas) atmosphere has enabled nanotubes of HfS2, ZrS2, and TiS2 to be synthesized and characterized. The dimensions of the nanotubes formed depend on the Group 4 metal used. The transmission electron micrograph image shows nanotubular structures…
Casting silica nets: By repeated “nanocasting” it is possible to first obtain a negative of the SBA-15 structure, known as CMK-3, which is then used to produce another nanocast by impregnation with tetraethoxysilane and condensation. After calcination to remove the carbon, an ordered mesoporous silica is obtained, cal…