Materials Literature
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The nanoenvironment provided by the neighboring dendra characteristically influences the redox potentials and the photophysical properties of the tetraphenylporphyrin–zinc (Zn-TPP; denoted as P in Figure) chromophore within the dendrimers 1, which are based on C60 as a structure-determining core. Such functional dendr…
Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was utilized to study simple poly(ethylene glycol)s (PEG) and a series of amphiphilic copolymers prepared from PEG and dendritic molecules. For the amphiphilic copolymers with branched dendritic structures, MALDI-TOF spectrometry…
Despite the relevance to most aspects of crystallization, a comprehensive understanding of the kinetics of heterogeneous nucleation has not been well established yet. In this paper, a new kinetic model based on the “steady-state” approach will be put forward to describe both heterogeneous and homogeneous nucleation. A…
A method, using a Corbino disk sample geometry, is described and applied to study of resistive tails of sintered $YBCO$. When the transport current passes radially from the rim of the disk sample to its center, the two component potential drop signal is detected below $T_c$, which is due to (i) quasiparticles $W_q$ an…
We measured the temperature dependence of the linear high field Hall resistivity of La_0.67Ca_0.33MnO_3 (T_C=232K) and La_0.67Sr_0.33MnO_3 (T_C=345K) thin films in the temperature range from 4K up to 360K in magnetic fields up to 20T. At low temperatures we find a charge carrier density of 1.3 and 1.4 holes per unit c…
Orange− or yellow−orange-colored aqueous dispersions of ultrafine gold particles (∼2 nm) result from the γ-irradiation of deaerated solutions containing hydrolyzed AuCl 4 - and poly(vinyl alcohol) or poly(vinylpyrrolidone), respectively. The particles have a weak and very broad plasmon absorption band with maximum in…
The solvent-free condensation of pyrrole and pentafluorobenzaldehyde (and to a lesser extent other electron-poor aldehydes as well) leads to a variety of products, of which three have been isolated and fully characterized. The two main products (11% each) are an open-chain pentapyrrole and corrole, a tetrapyrrolic mac…
A homologous series of cellulose oligomers from two to eight repeating subunits have been isolated and size-fractionated from the hydrolysis products of microcrystalline cellulose. Chemical modification of cellotriose ( 1 ), cellotetraose ( 2 ), cellopentaose ( 3 ), and cellohexaose ( 4 ) to the corresponding β-methyl…
We conclude from 23Na and 51V NMR measurements in NaxV2O5(x=0.996) a charge ordering transition starting at T=37 K and preceding the lattice distortion and the formation of a spin gap Delta=106 K at Tc=34.7 K. Above Tc, only a single Na site is observed in agreement with the Pmmn space group of this first 1/4-filled l…
A continuum model of crystalline solid equilibrium is presented in which the underlying periodic lattice structure is taken explicitly into account. This model also allows for both point and line defects in the bulk of the lattice and at interfaces, and the kinematics of such defects is discussed in some detail. A Gib…
We develop a theoretical framework for the diffusion of a single unconstrained species of atoms on a crystal lattice that provides a generalization of the classical theories of atomic diffusion and diffusion-induced phase separation to account for constitutive nonlinearities, external forces, and the deformation of th…
Grand canonical Monte Carlo (GCMC) simulations of ethylene physisorption on the basal plane of graphite are reported. The calculated isotherms are compared with experimental results at several temperatures. The maximum surface coverage studied is close to one monolayer. The ethylene molecules are described as six Lenn…
A thermodynamic framework (UNIQUAC model with temperature dependent parameters) is applied to model the salt-induced protein crystallization equilibrium, i.e., protein solubility. The framework introduces a term for the solubility product describing protein transfer between the liquid and solid phase and a term for th…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTImproved Polypyrrole/Silicon Junctions by Surfacial Modification of Hydrogen-Terminated Silicon Using Organolithium ReagentsNamyong Y. Kim and Paul E. LaibinisView Author Information Departments of Chemistry and Chemical Engineering Massachusetts Institute of Technolog…
A stable aqueous lead sol (10 nm particles) is formed upon the γ-irradiation of Pb(ClO 4 ) 2 in the presence of (poly)ethyleneimine. Lead nanoparticles have an absorption band at 218 nm with ε = 3.2 × 10 4 M -1 cm -1; the band appears at the wavelength that is expected for a surface plasmon oscillation. The changes in…
The deformation behavior of poly(styrene- b -butyl methacrylate) diblock copolymers, PS- b -PBMA, is studied by high-voltage electron microscopy (HVEM) with in-situ deformation device and by TEM. This allows us to describe the craze growth and propagation in block copolymers with different morphologies. The influence…
Herein we introduce the concept of an “activated” monomer approach to the synthesis of convergent dendrimers. In this method a set of chemically orthogonal monomers, one of which is an “activated” analogue of the other, is used to rapidly synthesize large, perfect dendrimers with one additional generation being added…
The 364 nm negative ion photoelectron spectrum of WO 2 - is obtained. The spectrum reveals that four different electronic states are accessed in the neutral molecule following electron detachment. From the rich vibrational structure the vibrational frequencies of the bending and/or symmetric stretching vibrations are…
We report simulations of water confined between two parallel flat (hydrophobic) walls separated by 10.95 Å. Our results are consistent with the possibility of a liquid−liquid phase transition separating two phases of different densities. The low-density liquid phase displays tetrahedral “ice-like” local ordering, whil…
Several new Ni ( 7a − i ), Pd ( 8a − j ), and Pt ( 9a − j ) dithiolenes belonging to the general class [M(R,R‘timdt) 2 ] (R,R‘timdt = monoanion of di-substituted imidazolidine-2,4,5-trithione) have been synthesized by sulfuring the disubstituted imidazolidine-2-thione-4,5-diones ( 4 ) with Lawesson's reagent ( 5 ) in…