Materials Literature
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We report a spectroscopic study of single colloidal $\mathrm{CdSe}/\mathrm{ZnS}$ nanocrystals at low temperature. We use photon-correlation Fourier spectroscopy, a technique based on measuring the correlations of the intensities detected at the outputs of a Michelson interferometer. Spectral diffusion over a few $\ens…
The recently proposed bipolaron model for large “organic magnetoresistance” (OMAR) at room temperature is extended to an analytically solvable two-site scheme. It is shown that even this extremely simplified approach reproduces some of the key features of OMAR, viz., the possibility to have both positive and negative…
The electromagnetic response of H-fractal structures, consisting of self-similar metallic lines or slits in metallic films deposited on silicon substrate, has been investigated in the terahertz region. The subwavelength fractal structure was observed to display electric resonances, with redshift in the resonant freque…
We investigate the spin state of $\mathrm{La}\mathrm{Co}{\mathrm{O}}_{3}$ using state-of-the-art photoemission spectroscopy and ab initio band structure calculations. The $\mathrm{GGA}+U$ calculations provide a good description of the ground state for the experimentally estimated value of electron correlation strength…
Raman spectra of single crystal ammonia borane, NH3BH3, were recorded as a function of temperature from 88 to 300 K using Raman microscopy and a variable temperature stage. The orthorhombic to orientationally disordered tetragonal phase transition at 225 K was clearly evident from the decrease in the number of vibrati…
A convenient 4-step (2-pot) approach for the synthesis of biocompatible, double hydrophilic linear-hyperbranched block copolymers based on poly(ethylene oxide) (PEO) and poly(glycerol) (PG) is described. The polymers consisting exclusively of an aliphatic polyether structure were prepared from linear PEO- b -( l -PG)…
A route to unravel and the complexities of polyoxometalates in solution using electrospray mass spectrometry is presented. This reveals the limited speciation of the clusters in organic solvent compared to that in aqueous solution and allows the unambiguous assignment of the protonation states of the cluster as a func…
We report the first experimental study of a model system of a two-dimensional colloidal crystal in a random pinning potential. The colloidal crystal consists of monodispersed charged polystyrene microspheres suspended in deionized aqueous media and confined near a rough charged surface. It is found that the static ori…
Abstract The study of the effect of the diisocyanate structure on the microstructure and macroscopic properties of polyurethanes was the main aim of this work. Biodegradable segmented thermoplastic elastomeric polyurethanes based on a poly(hexamethylene carbonate‐ co ‐caprolactone)diol (PHM‐ co ‐PCL) as soft segment w…
Abstract The deposition of micro‐ and nanocrystalline bismuth telluride thin films with tailored structure and composition is of interest in view of improving the well‐known material thermoelectric properties. Only a few works exist that discuss Raman scattering of Bi 2 Te 3 crystals and films, while a Raman character…
Abstract A method is presented to analyze XPS spectra recorded from thin (<5 nm) oxide layers with known thickness on corresponding metal substrates. With this method, the contribution of the oxide overlayer can be separated from the metal substrate for the metal core level line, even when the difference in binding…
A new route to bottom-up organic nanotechnology is presented. Molecular building blocks with specific optoelectronic properties are designed and grown via directed self-assembly arrays of morphologically controlled light-emitting organic nanofibers on template surfaces. The fibers can be easily transferred from the gr…
We investigate electronic and magnetic structures of the Mn chains supported on the CuN surface using first-principle LSDA and LDA+U calculations. The isotropic exchange integrals and anisotropic Dzyaloshinskii-Moriya interactions between Mn atoms are calculated using Green function formalism. It is shown that the acc…
Calculations using the (exact) fermionic functional renormalization group are usually truncated at the second order of the corresponding hierarchy of coupled ordinary differential equations. We present a method for the systematic determination of higher order vertex functions. This method is applied to a study of tran…
The quantum spin Hall (QSH) state is a topologically non-trivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells. In this work we pred…
We present results from ab initio calculations of the mechanical properties of the rhombohedral phase (beta) of vanadium metal reported in recent experiments, and other predicted high-pressure phases (gamma and bcc), focusing on properties relevant to dynamic experiments. We find that the volume change associated with…
The diamagnetic-paramagnetic and insulator-metal transitions in LnCoO3 perovskites (Ln=La,Y, rare earths) are reinterpreted and modeled as a two-level excitation process. In distinction to previous models, the present approach can be characterized as a low-high-intermediate spin LS-HS-IS scenario. The first level is t…
We consider the mutual effect of the electron-phonon and strong Coulomb interactions on each other by summing up leading logarithmic corrections via the renormalization group approach. We find that the Coulomb interaction enhances electron coupling to the intervalley ${A}_{1}$ optical phonons, but not to the intravall…
Die Biomineralisation von Siliciumdioxid in Diatomeen führt zu komplexen Zellwandstrukturen (siehe SEM-Bild) und hängt von strukturgebenden Matrizen ab, die durch die elektrostatische Zusammenlagerung positiv geladener Polyaminderivate und Polyanionen gebildet werden. Die untersuchten Peptide bilden eine Familie biolo…
Abstract Electrospinning was used to fabricate mats of poly(vinyl alcohol) (PVA; M w = 72,000 Da, degree of hydrolysis ≈ 97.5–99.5) nanofibers from PVA solutions in reverse osmotic water. The effects of solution concentration, applied electrical potential, sonication, and collection distance on morphological appearanc…