Materials Literature
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We investigate the low-frequency end of the vibrational spectrum in small (nanometric) disordered systems. Using numerical simulation and exact diagonalization for simple two-dimensional models, we show that continuum elasticity, applied to these systems, actually breaks down below a length scale of typically 30 to 50…
Polymer chains in colloid−polymer mixtures can be coarse-grained by replacing them with single soft particles interacting via effective polymer−polymer and polymer−colloid pair potentials. Here we describe in detail how Ornstein−Zernike inversion techniques, originally developed for atomic and molecular fluids, can be…
The 93Nb and 45Sc NMR spectra in PbSc_1/2Nb_1/2O_3 (PSN) and PbMg_1/3Nb_2/3O_3 (PMN) disordered relaxor ferroelectrics at the temperature T > T_0 (T_0 is the temperature of the dielectric susceptibility maximum) have been studied. Spectra analysis was performed on the base both of the analytical description of NMR lin…
The maximum current-perpendicular-to-plane giant magnetoresistance is searched for in magnetic multilayers made of Co, Ni, and Cu with disorder levels similar to those found in room temperature experiments. The calculation is made possible by a highly optimized linear response code, which uses the impurity averaged Gr…
The new salts trans-4′-(dimethylamino)-N-R-4-stilbazolium hexafluorophosphate (R = methyl, Me 1, phenyl, Ph 2, 2,4-dinitrophenyl, DNPh 3, 2-pyrimidyl, Pym 4, Scheme 1) have been prepared. Their electronic absorption spectra show intense, visible intramolecular charge-transfer bands, the energy (Emax) of which decrease…
We explore the distance fluctuation criterion (“Lindemann criterion”) for melting transitions. Distances from average positions in accord with Lindemann, or interparticle distances, in accord with Jellinek and Berry or Etters and Kaelberer, are examined. The primary goal is to determine which of these offers the more…
In situ rheo-optical techniques are combined with synchrotron wide-angle X-ray diffraction (WAXD) to investigate the oriented crystallization precursors that develop upon strongly shearing an isothermal melt of polydisperse isotactic polypropylene (iPP). The “short-term shearing” experimental protocol, developed by Ja…
gamma-Al2O3 is one of the most extensively utilized metal oxides in heterogeneous catalysis. Conventional forms of this oxide typically exhibit a surface area and pore volume less than 250 m2/g and 0.5 cm3/g, respectively. Previous efforts to prepare mesostructured forms of alumina resulted only in structurally unstab…
Advanced materials with large and dynamic variation in thermal properties, sought for urgent defense and space applications, have heretofore been elusive. Conducting polymers (CPs) have shown some intrinsic variation of mid- to far-infrared (IR) signature in this respect, but the practical utilization of this has rema…
Optically active metallosalens are currently one of the most widely used catalysts for asymmetric synthesis. This is mainly due to the following reasons: various salen [N,N′-ethylenebis(salicyldeneaminato)] ligands form complexes with many metal ions and the resulting metallosalens adopt versatile structures, therefor…
Transparent and conductive ZnO thin films have been prepared by a method derived from chemical vapor deposition using Zn (C5H7O2)2 as Zn source. The deposited thin ZnO layers of ∼0.1 μm thickness on Si and InP semiconductor substrates, have been investigated with respect to the crystalline phase by X-ray diffraction (…
Bulk polymerizations of ε-caprolactone (CL) were conducted at 130 °C, in which the structure and amount of initiator were varied. Polymerization induction periods were observed and attributed to slow heat transfer and to the type of alcohol used as initiator. Induction periods persisted until virtually complete consum…
The occurrence of metallic conductivity in SrTiO3 single crystals is reported for reduction under low partial pressure of oxygen at 800 degrees C. This transition is shown to result from the formation of a high concentration of vacancy defects along a network of extended defects within the skin region. A self-healing…
Many biological organisms contain specialized structures composed of inorganic materials. Cellular processes in vivo facilitate the organized assembly of mineral building blocks into complex structures. The structural hierarchy and complexity across a range of length scales are providing new ideas and concepts for mat…
The first report of the full-length structure of the collagen-like polypeptide [(Pro-Pro-Gly)(10)](3) is given. This structure was obtained from crystals grown in a microgravity environment, which diffracted up to 1.3 A, using synchrotron radiation. The final model, which was refined to an R(factor) of 0.18, is the hi…
The synthesis and applications of organic-inorganic nanostructured colloids and colloidal-based materials are reviewed here. Emphasis is placed on the strategies and synthetic methods developed to organize organic-inorganic architectures. The article begins with a description and a general hierarchical classification…
We have studied the effect of weak solute−solvent attractions on the solvation of nonpolar molecules in water at ambient conditions using an extension and improved parameterization of the theory of solvation due to Lum, Chandler, and Weeks [ J. Phys. Chem. B 1999, 103, 4570]. With a reasonable strength of alkane−water…
The effects of the deacetylation degree (DD) and preparation methods for chitosan on antimicrobial activity were evaluated. Chemically prepared chitin (CH-chitin) and microbiologically prepared chitin (MO-chitin) were obtained from shrimp shells. The CH-chitin and MO-chitin were further chemically deacetylated to obta…
Erbium-doped ZrO 2 nanoparticles are prepared by a sol−emulsion−gel technique. The effects of the Er 3+ concentration and different codopants (Yb 3+ and Y 3+ ) in the ZrO 2 matrix on the upconverted emission are reported. Green and red upconversion emission at 550 and 670 nm were observed from these oxide nanocrystals…
This paper is intended to show how the control of the optical response of regular arrays of gold nanoparticles allows to improve our understanding of surface-enhanced Raman scattering (SERS). Regular particle arrays, designed by electron-beam lithography, exhibit remarkable optical properties and appear to be suitable…