Materials Literature
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Thin layer electrodes (0.2−0.5 μm) of highly organized nanotextured anatase were prepared by hydrolysis of TiCl 4 in the presence of poly(alkylene oxide) block copolymer, Pluronic P-123, acting as the structure-directing agent. Electrochemical properties of these layers were studied in KCF 3 SO 3 + propylene carbonate…
Palladium nanoparticles (2−3 nm in diameter) have been prepared within covalently functionalized poly(propylene imine) (PPI) dendrimers, and the resulting composite materials are shown to be effective for Heck coupling reactions. Two novel concepts are demonstrated in this report. The first concept involves the incorp…
The interrelation between particle size, crystal structure and optical properties in semiconductor quantum dots has elicited widespread interest. We report the first attempt at relating the size-induced transformation from a hexagonal to a cubic structure in CdS nanoparticles to a change in the band gap. CdS nanoparti…
Silver complexes of poly(amidoamine) (PAMAM) dendrimers as well as different {silver−PAMAM} dendrimer nanocomposite solutions have been tested in vitro against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli bacteria, using the standard agar overlay method. Both PAMAM silver salts and nanocomposite…
We demonstrate high-quality, highly fluorescent, ZnSe colloidal nanocrystals (or quantum dots) that are doped with paramagnetic Mn 2+ impurities. We present luminescence, magnetic circular dichroism (MCD), and electron paramagnetic resonance (EPR) measurements to confirm that the Mn impurities are embedded inside the…
Photoluminescence in the visible domain can be observed in amorphous silicon nitride (a-SiNx) alloys prepared by evaporation of silicon under a flow of nitrogen ions. A strong improvement of the photoluminescence intensity was obtained with annealing treatments in the range 500–1150 °C. Structural investigations were…
A first-principles-derived approach is used to study the properties of rocksalt-ordered and disordered Pb(Sc0.5Nb0.5)O3 (PSN) alloys. The paraelectric-to-ferroelectric transition temperature Tc is strongly dependent on the atomic configuration, while the piezoelectric response versus T/Tc is nearly independent of the…
It is demonstrated that the nonrelativistic high energy $\ensuremath{\omega}\ensuremath{\rightarrow}\ensuremath{\infty}$ behavior of the photoionization cross section of an $\mathrm{nl}$ atomic subshell, ${\ensuremath{\sigma}}_{\mathrm{nl}}(\ensuremath{\omega})$, for $l>0$ is independent of $l$ and is given by ${\e…
Benefitting from the long path inside planar waveguides, we have investigated the optical losses of porous silicon, in the continuous 0.8–1.6 μm (0.77–1.55 eV) range. The obtained values, typically a few cm−1, are 1 order of magnitude larger than “pure” absorption losses measured previously. The other main sources of…
Mössbauer and magnetic studies have shown that 1–2 wt % of SiO2 could be dissolved in the CoFe2O4 structure. Changes in magnetization and Curie temperature were observed. The presence of SiO2 might enhance magnetic anisotropy. Coercivity values of up to 3.5 kOe were measured for mechanically alloyed CoFe2O4/SiO2 powde…
We report on the growth of polarity-controlled ZnO films by plasma-assisted molecular-beam epitaxy. Different polar (Zn- and O-polar) ZnO films on unipolar (Ga-polar) GaN epilayers are selectively grown. Polarity of ZnO films is evaluated by coaxial impact collision ion scattering spectroscopy. Zn preexposure prior to…
We show that germanium dots can be directly grown by molecular beam epitaxy (MBE) on a silicon (001) surface covered by a thin (1.2-nm-thick) thermal silicon oxide layer. We describe the experimental procedure, which induces the growth of a high density (1011/cm2) of nanometric germanium dots on silicon oxide. Germani…
Longitudinal or transverse magnetic fields applied on a crystal of ${\mathrm{Mn}}_{12}$ acetate allows one to observe independent tunnel transitions between $m\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}S+p$ and $m\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}S\ensuremath{-}n\ensuremath{-}p$…
The crossover between thermally assisted and pure quantum tunneling has been studied in single crystals of high spin (S = 10) uniaxial molecular magnet Mn12 using micro-Hall-effect magnetometry. Magnetic hysteresis and relaxation experiments have been used to investigate the energy levels that determine the magnetizat…
The self-energy of the photohole in 2H-TaSe2 is measured by angle-resolved photoemission spectroscopy as a function of binding energy and temperature. In the charge-density wave (CDW) state, a structure in the self-energy is detected at approximately 65 meV that cannot be explained by electron-phonon scattering. A red…
Spin-dependent tunneling has been shown to occur through Ga2O3 as the insulating tunnel barrier. Magnetic tunnel junctions of the type Co/Ga2O3/Ni80Fe20 were prepared by oxidizing thin metal layer of Ga in oxygen plasma and characterized. The highest junction magnetoresistance observed was 18.2% at room temperature, i…
Ferroelectric intergrowth Bi4Ti3O12–SrBi4Ti4O15 has been demonstrated to have a large remanent polarization (2Pr) of 30 μC/cm2 and a high Curie temperature of 610 °C using bulk ceramics. The Rietveld analysis of the powder x-ray diffraction patterns showed that there are two kinds of Bi ions in Bi2O2 layers. One Bi io…
Carbon nanotube junctions are predicted to exhibit negative differential resistance, with very high peak-to-valley current ratios even at room temperature. We treat both nanotube p-n junctions and undoped metal-nanotube-metal junctions, calculating quantum transport through the self-consistent potential within a tight…
We study the response of an adsorbed monolayer under a driving force as a model of sliding friction phenomena between two crystalline surfaces with a boundary lubrication layer. Using Langevin-dynamics simulation, we determine the nonlinear response in the direction transverse to a high symmetry direction along which…
Effects of induced biaxial strain on the electrical transport and magnetic properties of epitaxial thin films of SrRuO3 and La0.67Sr0.33MnO3 by structural transitions of ferroelectric BaTiO3 substrates have been studied. Large jumps of electrical resistivity (∼5% in SrRuO3 and ∼12% in La0.67Sr0.33MnO3) and low field m…