Materials Literature
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We report on quantitative calculations of the upper critical field $H_{c2}$ for clean type-II superconductors Nb, NbSe$_{2}$, and MgB$_{2}$ using Fermi surfaces from {\em ab initio} electronic structure calculations. The results for Nb and NbSe$_2$ excellently reproduce both temperature and directional dependences of…
Recently it has been predicted that a spin-polarized electrical current perpendicular-to-plane (CPP) directly flowing through a magnetic element can induce magnetization switching through spin-momentum transfer. In this letter, the first observation of current-induced magnetization switching (CIMS) in exchange-biased…
This article presents a new and efficient alternative to well established algorithms for molecular geometry optimization. The new approach exploits the approximate decoupling of molecular energetics in a curvilinear internal coordinate system, allowing separation of the 3N-dimensional optimization problem into an O(N)…
In the vapor−liquid−solid (VLS) growth of 1D nanostructures, the electronic structure of the substrate surface may critically affect the morphology of the grown nanowires/nanorods. In this paper, using a model system of the Sn-catalyzed growth of ZnO nanostructures on a single-crystal ZnO substrate, we demonstrate the…
In conjugated polymers the concept of spectroscopic units belonging to different spatial segments of the chain, which are responsible for the spectroscopic properties of the polymer, has been used to explain the spectral heterogeneity and the excitation migration by (Förster type) hopping transfer. In the present work…
The temporal evolution of fluorescence from isolated single-wall carbon nanotubes (SWNTs) has been investigated using optical Kerr gating. The fluorescence emission is found to decay on a time scale of 10 ps. This fast relaxation arises from nonradiative processes, the existence of which explains the relatively low ob…
Synthetic giant multiporphyrin arrays with well-defined architectures are reviewed in terms of artificial light-harvesting materials. Meso,meso-linked porphyrin arrays and multiporphyrin dendrimers have successfully mimicked the light-harvesting function of bacterial photosynthetic systems. We have also developed nove…
Differential pulse voltammetry (DPV) of TOPO-capped CdTe nanoparticles (NPs) in dichloromethane and a mixture of benzene and acetonitrile showed two anodic and one cathodic peaks of the NPs themselves and an additional anodic peak resulting from the oxidation of reduced NPs. The electrochemical band gap (∼2.1 eV) betw…
This paper describes electrochemical and spectroscopic properties of a well-characterized, synthetically accessible, 1.1 nm diam Au nanoparticle, Au(38)(PhC(2)S)(24), where PhC(2)S is phenylethylthiolate. Properties of other Au(38) nanoparticles made by exchanging the monolayer ligands with different thiolate ligands…
Poly(dimer acid-brassylic acid) [P(DA-BA)] copolymers and poly(dimer acid-pentadecandioic acid) [P(DA-PA)] copolymers were prepared by melt polycondensation of the corresponding mixed anhydride prepolymers. The copolymers were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), dif…
Abstract The tensile stress relaxation behavior subsequent to different imposed strains of poly(1‐butene) was studied at room temperature. The plastic and elastic strains after a stress relaxation practically agree with those found for an immediate unloading. This indicates that the same decomposition of the total str…
The dielectric permittivity of the orientational glass $\mathrm{methanol}(x=0.73)\ensuremath{-}\ensuremath{\beta}$-hydroquinone-clathrate has been studied as function of temperature and waiting time using different temperature-time protocols. We study aging, rejuvenation, and memory effects in the glassy phase and dis…
Abstract A series of phosphorus‐containing dendrons is synthesized starting from a unique precursor (EtO) 2 P(O)CH=CHC 6 H 4 PPh 2 ( 3‐G 0 ), whose X‐ray crystal structure shows an extended planarity between both phosphorus. Staudinger reactions with functionalized azides on the phosphino group are the first step for…
We study the formation of engineered ferroelectric domains in two dimensions based on a continuum approach that incorporates the long-range elastic and electrostatic interactions. The model is also used to simulate the piezoelectric properties of the engineered domain configurations and the response is compared with t…
Quadrupole resonance (QR) technology for the detection of explosives is of crucial importance in an increasing number of applications. For landmine detection, where the detection system cannot be shielded, QR has proven to be highly effective if the QR sensor is not exposed to radio-frequency interference (RFI). Howev…
We present an electron energy-loss study of the nature of the low-lying singlet excitations in quasi-one-dimensional copper phthalocyanine molecular crystals. The observed variation of the spectral weight at different excitation energies strongly indicates the presence of two types of excitations near the excitation o…
We have designed, fabricated, and tested laser mirrors made entirely from porous silicon (PSi). PSi high reflectors and output couplers were designed for continuous-wave and mode-locked Ti:Sapphire lasers that were tuned between 730 nm and 940 nm. The mode-locked version of this laser produced 80 fs pulses at 85 MHz,…
Abstract The solution reaction of orotic acid (2,6‐dioxo‐1,2,3,6‐tetrahydropyrimidine‐4‐carboxylic acid, H 3 dtpc) and Ln(NO 3 ) 3 ·6H 2 O (Ln = La, Ce) or Ln 2 O 3 (Ln = Pr, Nd) yielded five complexes [{Ln( a H 2 dtpc) 2 ( b H 2 dtpc)(H 2 O) 4 }·H 2 O] n (Ln = La 1 , Ce 3 ), [La( a H 2 dtpc) 2 ( c H 2 dtpc)(H 2 O) 6…
In this study, we have extended the knowledge of the dynamics of polycarbonate (PC) far below ${T}_{g}$ by means of positron annihilation lifetime spectroscopy (PALS), which is able to detect the isothermal relaxation of the free volume after rejuvenation above ${T}_{g}.$ The free volume relaxation patterns at differe…
Abstract Various dinucleating pyrazole ligands with chelating side arms in the 3‐ and 5‐positions of the heterocycle have been shown to form Ni II /azido complexes, where the metal ions are spanned by the pyrazolate, and an azido bridge. Four new complexes have been characterized by X‐ray crystallography and variable‐…