Materials Literature
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The spin-polarization patterns of a weakly coupled triplet−doublet spin pair are studied in a covalently linked copper (II)−free base porphyrin dimer partially oriented in a liquid crystalline solvent. The triplet−doublet pair is generated in the dimer by either spin−orbit intersystem crossing (ISC) within the free-ba…
The identity of reactive intermediates and of active sites and the details of redox cycles and oxygen removal pathways during NO decomposition on well-characterized Cu−ZSM5 were examined by combining previous spectroscopic and steady-state kinetic studies with measurements of the rate of evolution of NO, N 2 O, NO 2,…
Abstract The crystallization of polymer films in a temperature gradient was simulated. The curvature of lamella growth directions observed experimentally was taken into account. The computer simulation permitted the visualization of the evolution of the spherulitic pattern and also the calculation of the conversion of…
We report a detailed experimental study of the aging of the (initial) random hexagonal close-packed (rhcp) crystals formed in suspensions of hard-sphere colloids near the melting point. By suspending the same colloidal particles in two different mixtures of solvents we are able to tune the strength of the gravitationa…
[structure: see text] Oligothienyl-substituted paracyclophanes bearing alpha-thienyl substituents, which block polymerization at these sites, undergo oxidation to form stable radical cations and dications. Splitting of the first voltammetric oxidation wave of stacked dimers into two single-electron processes correspon…
Diamond is impressive because of its wide range of extreme properties. By most measures, diamond is ‘the biggest and best’: it is the hardest known material, has the lowest coefficient of thermal expansion, is chemically inert and wear resistant, offers low friction, has high thermal conductivity, and is electrically…
The switching behavior of 1,2-bis(5-phenyl-2-methylthien-3-yl)cyclopentene is studied by means of polarization selective nonlinear optical spectroscopy and time-dependent density functional theory. The combined information from the observed population and orientational dynamics together with the results of theoretical…
Abstract The effect of thermal treatment on the crystalline and supermolecular structure of polylactide was investigated. The samples were isothermally crystallized by two methods, the crystallization temperature being reached (1) via cooling from the melt and (2) via heating from the glassy, amorphous state. The samp…
Abstract New bisphenol monomers, (3‐methyl)phenylhydroquinone and (3‐trifluoromethyl)phenylhydroquinone, were prepared in a two‐step synthesis. A series of poly(aryl ether ketone)s were derived from these bisphenols via a nucleophilic aromatic substitution polycondensation with various bisfluoro compounds. The polycon…
Three-dimensionally ordered mesoporous niobium oxide was prepared by a neutral templating route with the addition of a trace amount of cations, which have 5- and 2-nm pore diameter and wall thickness, respectively.
Abstract We have been investigating the synthesis of quantum dots of CdSe, CuInS 2 , and CuInSe 2 for use in an intermediate bandgap solar cell. We have prepared a variety of quantum dots, using the typical organometallic synthesis routes pioneered by Bawendi et al. in the early 1990s. However, unlike previous work in…
We develop a general theory of electron--hole recombination in organic light emitting diodes that leads to formation of emissive singlet excitons and nonemissive triplet excitons. We briefly review other existing theories and show how our approach is substantively different from these theories. Using an exact time-dep…
The effect that an additional energy barrier E_{kr} for step adatoms moving around kinks has on equilibrium step edge fluctuations is explored using scaling arguments and kinetic Monte Carlo simulations. When mass transport is through step edge diffusion, the time correlation function of the step fluctuations behaves…
The Hall resistivity, magnetoresistance, and magnetization of La_{1-x}Ca_{x}CoO_{3} epitaxial films with x between 0.25 and 0.4 grown on lanthanum aluminate were measured in fields up to 7 T. The x=1/3 film, shows a reentrant metal insulator transition. Below 100 K, the x=1/3 and 0.4 films have significant coercivity…
Human malaria, one of the most striking, reemerging infectious diseases, is caused by several types of Plasmodium parasites. As the parasite digests hemoglobin in human red blood cells, the heme byproduct crystallizes into micron-sized malaria-pigment (hemozoin). Making use of a recently reported powder-crystal struct…
We present an experimental and theoretical study of the conduction states of crystalline Si films confined within amorphous SiO_2 barriers, using the Si-2p core-level excitations. The spectral peaks near the conduction band minimum are compared with the bulk silicon spectrum. In the Si quantum wells, it is found that…
Performing light scattering experiments we show that introducing short-ranged attraction to a colloid suspension of nearly hard spheres by addition of a free polymer produces new glass-transition phenomena. We observe a dramatic acceleration of the density fluctuations amounting to the melting of a colloidal glass. Up…
The science of surface and colloid chemistry has been expanding at a rapid pace, resulting in new areas of development, additional applications, and more theoretical and experimental information on related systems. Completely revised and expanded to reflect the very active worldwide research on this subject, this is t…
Temperature-dependent measurements of luminescent intensity and lifetimes of the ${4f}^{2}{[}^{1}{\stackrel{\ensuremath{\rightarrow}}{{S}_{0}}}^{1}{I}_{6}]$ and ${4f}^{1}{5d}^{1}\ensuremath{\rightarrow}{4f}^{2}$ emission for ${\mathrm{BaSO}}_{4}:{\mathrm{Pr}}^{3+}$ were performed. It was found that the intensity of th…
We investigate the electromagnetic mechanism in surfaceenhanced Raman scattering (SERS) from randomly rough metal surfaces with Gaussian statistics and Gaussian correlation function. By means of rigorous numerical calculations, large average SERS enhancement factors (above 104) are encountered when the correlation len…