Materials Literature
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A well-defined amine-functionalized silica surface displaying evidence of isolated amine sites is prepared using a molecular patterning technique. A tritylimine patterning agent is used to spatially position the amine sites a minimum distance from each other, resulting in an organic loading of 0.345 mmol of NH 2 /g of…
We have computed absorption and emission energies of silicon nanocrystals as a function of size and of surface passivants, using both density functional theory and quantum Monte Carlo calculations. We have found that the ionic rearrangements and electronic relaxations occurring upon absorption and emission are extreme…
Through manipulating crystal growth directions, we devised a versatile synthetic method to fabricate complex alpha-MoO(3) nanostructures with external bonding capacity for self-organization. Using four-armed forklike alpha-MoO(3) as nanobuilding blocks, we assembled more complex crystal morphologies, such as centrally…
Model polylactide-b-polyisoprene-b-polylactide (PLA-PI-PLA) triblock copolymers were prepared by an efficient protocol starting with alpha,omega-dihydroxy polyisoprene (HO-PI-OH). Using a moderately electrophilic Al(O-i-Pr)(3) catalyst and carefully controlling the ratio of Al to HO-PI-OH avoided gel formation and res…
We investigate strong-coupling superfluidity in a uniform gas of Fermi atoms attractively interacting via quasi-molecular bosons associated with a Feshbach resonance. This interaction is tunable by the threshold energy $2ν$ of the Feshbach resonance, becoming large as $2ν$ is decreased. In recent work, we showed that…
Electron spin polarizations of 32% are obtained in a GaAs quantum well via electrical injection through a reverse-biased Fe/AlGaAs Schottky contact. An analysis of the transport data using the Rowell criteria demonstrates that single step tunneling is the dominant transport mechanism. The current-voltage data show a c…
Fourteen titanium alkoxides were synthesized for comparison of their catalytic properties in the bulk and solution polymerization of lactide (LA). In bulk polymerizations, they are effective catalysts in terms of polymer yield and molecular weight. Titanatranes gave polylactides with significantly increased molecular…
Electron-hole (e-h) capture in luminescent conjugated polymers (LCPs) is modeled by the dissipative dynamics of a multilevel electronic system coupled to a phonon bath. Electroinjected e-h pairs are simulated by a mixed quantum state, which relaxes via phonon-driven internal conversions to low-lying charge-transfer (C…
Abstract We report comparisons of electron inelastic mean free paths (IMFPs) determined from our predictive IMFP equation TPP‐2M and reference IMFPs calculated from optical data. These comparisons were made for values of the parameter N v (the number of valence electrons per atom or molecule) that we have recommended…
Fluorescence and two-photon excitation (TPE) spectra are reported for a single crystal of the elpasolite, Cs2NaTbBr6, at low temperatures. Energy levels of the f8 Tb(III) manifold are located and assigned in the range up to 39 400 cm−1 A cubic to tetragonal phase transition occurs below ∼155K. Small spectral splitting…
Electron–phonon coupling and the normal and possible superconducting states in the monoanions of B, N-substituted acenes such as B3N3H6, B5N5H8, and B7N7H10 are studied. The results for B, N-substituted acenes are compared with those for acenes. The B–N stretching modes around 1500 cm−1 and the low-frequency modes, le…
The structural evolutions of glassy carbon (GC) and graphitized glassy carbon (GGC) treated under high temperatures and high pressures have been studied by energy-dispersive x-ray diffraction in a diamond anvil cell. The equations of state of GC and GGC are determined from x-ray density data. GC has a higher bulk modu…
The luminescence from conjugated polyelectrolytes that contain pendant metal complex units is quenched very efficiently by oppositely charged electron acceptors.
The intergrain magnetoresistance (IMR) of polycrystalline Sr2FeMoO6 is known to depend on its grain size and the tunnel barrier thickness formed during fabrication. Further enhancement of the IMR of Sr2FeMoO6 is found possible by further decreasing its grain size using high-energy ball milling, as well as by judicious…
We show experimentally that a layer of silicon nanocrystals, prepared by the Si-ion implantation (with the energy of 400 keV) into a synthetic silica slab and exhibiting room-temperature red photoluminescence, can serve simultaneously as a single-mode planar optical waveguide. The waveguide is shown to self-select gui…
I consider a brush of gradient polymers, with the chains anchored at their pure A ends with the chemical composition changing linearly along the chain up to the untethered chain tips whose composition is pure B. Demixing of the A and B monomers results in the creation of a thermally-controllable zone from which free e…
The relaxation dynamics of a rubbed polystyrene (PS) surface have been characterized using infrared-visible sum frequency generation spectroscopy (SFG). The SFG results were compared with previous relaxation of retardation measurements, and the results show that the rubbed PS surface has the same T(g) as the bulk wher…
Primary nucleation of poly(vinylidene fluoride) (pVDF) from bulk entangled amorphous polymer melts has been observed from molecular dynamics (MD) simulations. This is the first instance of spontaneous primary nucleation of an entangled bulk polymer in a MD simulation. The melt-to-crystal phase transition occurs via a…
Poly(L-lactic acid) samples of varying regio regularity were studied by static and dynamic laser light scattering in conjunction with Raman spectroscopy. Light scattering results allow an estimate of the characteristic ratio, C∞. Experimental values were compared to the characteristic ratio computed from structural pa…
We report Monte Carlo simulations of the melting of a single-polymer crystallite. We find that, unlike most atomic and molecular crystals, such crystallites can be heated appreciably above their melting temperature before they transform to the disordered “coil” state. The surface of the superheated crystallite is foun…