Materials Literature
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We present a theoretical approach to calculate the {\it local} absorption spectrum of excitons confined in a semiconductor nanostructure. Using the density-matrix formalism, we derive a microscopic expression for the non-local susceptibility, both in the linear and non-linear regimes, which includes a three-dimensiona…
We reported a systematic change in the average magnetic relaxation rate, after the application and removal of a 5 T magnetic field, in a polycrystalline sample of La0.5Ca0.5MnO3. Magnetic relaxation measurements and magnetization versus field curves were taken from 10 K to 160 K. The long time behavior of the relaxati…
Coiled-coil motifs provide simple systems for studying molecular self-assembly. We designed two 28-residue peptides to assemble into an extended coiled-coil fiber. Complementary interactions in the core and flanking ion-pairs were used to direct staggered heterodimers. These had "sticky-ends" to promote the formation…
A novel molecular triad, representing an artificial reaction center, was synthesized via linking a fullerene moiety to an array of two porphyrins (i.e., a zinc tetraphenyl porphyrin (ZnP) and a free base tetraphenyl porphyrin (H 2 P)). In this ZnP−H 2 P−C 60 triad, the ZnP performs as an antenna molecule, transferring…
A new experimental method is presented using fluorescein dye to determine the spatial and temporal variations of the liquid volume fraction in aqueous foams. This method is used for quantitative studies of liquid redistribution ( drainage ) in three types of experiments: forced, free, and pulsed drainage. Characterist…
Photoinduced magnetization has been recently evidenced by Hashimoto et al. in CoFe Prussian blue analogues. We synthesized three compounds with a variable cobalt environment to point out the conditions required to observe the photoinduced magnetization. Structure and electronic structure of the compounds have been inv…
The deformation behavior of poly(styrene- b -butyl methacrylate) diblock copolymers, PS- b -PBMA, is studied by high-voltage electron microscopy (HVEM) with an in-situ tensile device. While in the first part the phase behavior of PS- b -PBMA diblock copolymers is investigated via small-angle neutron scattering (SANS),…
Full-potential linear-muffin-tin-orbital molecular-dynamics calculations have been performed to investigate the structures and energies of ${\mathrm{Si}}_{20}$ clusters. Among the selected 15 stable structures for ${\mathrm{Si}}_{20},$ the most stable structure is constructed by stacking ${\mathrm{Si}}_{9}$ tricapped…
As part of the U.S. nonproliferation effort, we are investigating the conversion of the production of fission-product 99 Mo from use of high-enriched uranium (HEU) to low-enriched uranium (LEU). Successful conversion from HEU to LEU (<20% 235 U) requires an irradiation target that contains 5 times more uranium but min…
We report the frequency dependence of linear and nonlinear optical susceptibilities of H−silsesquioxanes of various cage sizes and conformations using the INDO/CI method coupled with the SOS method. The average dynamic refractive index of silsesquioxanes is found to decrease as the cage size increases, and its variati…
Different types of polymers can be intercalated into α-RuCl 3 with different synthetic methodologies. Polyaniline/α-RuCl 3 nanocomposite was prepared by the in situ redox intercalative polymerization method, in which α-RuCl 3 was exposed to an aniline/acetonitrile solution in open air. Water-soluble polymers such as p…
Films containing soy protein and wheat gluten were exposed to simulated farmland soil mix over a period of 30 days and monitored for degradation. The simulated farmland soil mix (topsoil/sand/Sunshine compost/vermiculite, 59:6:25:10, wt %) was mixed and stored at ambient humidity (48-55%) and temperature (20-24 degree…
Several oligothiophenes with 2-mesitylthio (MesS) substituents have been prepared and studied by UV−visible spectroscopy and cyclic voltammetry. These compounds can be considered as models for thiol-terminated conjugated oligomers, which have attracted intense interest as materials for molecular-scale electronics. Thr…
A series of 6-substituted indolinobenzospiropyrans were resolved by chiral stationary phase HPLC and rate constants k rac for their thermal racemization were measured by circular dichroism spectropolarimetry at 60 °C in three different solvents: cyclohexane, 90:10 hexanes/2-propanol, and acetonitrile. Results show tha…
Hydrogen adsorption in porous materials is one of the methods actively being studied to store hydrogen on board vehicles driven by fuel cells. Recent experiments and numerical simulations have shown that adsorbent materials appropriate to hydrogen storage could be made up of carbon nanotubes. In this work we study the…
A Fano resonance mechanism is evidenced to control the formation of optical Fermi-edge singularities in multi-subband systems such as remotely doped AlxGa1-xAs heterostructures. Using Fano parameters, we probe the physical nature of the interaction between Fermi-sea electrons and empty conduction subbands. We show tha…
An analysis of the morphological behavior of substrate-supported diblock copolymer films for thicknesses t below the equilibrium period L 0 of the copolymer is presented. Substrate-supported films generally exhibit dissimilar interactions between the copolymer block components and the free and substrate surfaces. Acco…
Micropatterned thin films have received increased interest in the past few years. Besides preparation by conventional lithography, self-assembly of materials around a template can be used for patterning. Recently a method that utilizes the condensation of micrometer-size water droplets on solutions of block copolymers…
Gelatin samples, native and chemically crosslinked with three different diisocyanates, were studied by bending-creep measurements. These samples were characterized by the number-average molecular weight of a chain segment between two points of crosslinkage Mc. The chemical network was found to contribute to a marked e…
Different modified polyamide (MPA) and modified polyethylene (MPE) resins were prepared by reactive extrusion of different contents of a compatibilizer precursor (CP) with either polyamide (PA) or polyethylene (PE). The MPE and MPA resins were then blow-molded with designed amounts of PA or PE resins to prepare four d…