Materials Literature
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Near-infrared luminescence is observed from single crystals of K 2 PdCl 4 and K 2 PdBr 4 between 13 500 cm - 1 and 9000 cm - 1 (740 nm and 1100 nm). The emission spectrum of K 2 PdBr 4 shows vibronic structure involving both the totally symmetrical a 1g mode and the non-totally symmetrical b 1g mode ( D 4 h point grou…
A layered mercury telluride, Rb 2 Hg 3 Te 4, was discovered during an exploration of hydro(solvo)thermal synthesis of tellurides at temperatures somewhat above the boiling point of ethylenediamine. Crystals of Rb 2 Hg 3 Te 4 were grown from solvothermal reactions using ethylenediamine as a solvent. Single crystal X-ra…
Raman, X-ray diffraction (XRD), UV−visible reflectance, and 13 C and 109 Ag CPMAS NMR studies have been carried out on three different forms of the layered solid AgS(CH 2 ) 3 CH 3: a white all-trans compound, a bright yellow gauche C(1)−C(2) conformational isomer, and a phase containing both species. The structure of…
A new tungstoboric species, [BW 13 O 46 H 3 ] 8 -, which was identified in solution, is an intermediate between [BW 11 O 39 H] 8 - and the so-called hexagonal acid. This heteropolyacid was obtained in high yield by a new synthetic route. A single-crystal X-ray diffraction study showed that its formula is H 21 [B 3 W 3…
For a series of copper(II) porphyrins, we report EPR data from solid solutions as well as E 0 values for the first ring oxidation, emission spectra, and luminescence lifetimes in methylene chloride. Although the EPR parameters are fairly constant, the potentials vary by almost 700 mV, and the room-temperature lifetime…
The species resulting from a typical preparation for metal-substituted hybrids of the Keggin tridecamer, Al 13 or [AlO 4 Al 12 (OH) 24 (OH 2 ) 12 ] 7+, were examined by performing 27 Al NMR on the solutions during aging and by studying the precipitated sulfate salts via solid state 27 Al NMR and powder X-ray diffracti…
The discrete trinuclear complex [(NEt 4 ){Mn(H 2 O)(5-Cl-salen)} 2 {Fe(CN) 6 }]·H 2 O, 3, and a two-dimensional heterometal assembly [(NEt 4 ){Mn(5-Cl-salen)} 2 {Fe(CN) 6 }] n, 4, have been prepared (NEt 4 = tetraethylammonium, 5-Cl-salen = N, N ‘-ethylenebis(5-chlorosalicylidene)aminato) dianion). Compound 4 crystall…
An alternating di-(μ-(end-on)azido)−di-(μ-(end-to-end)azido) manganese(II) one-dimensional compound, with formula [Mn(bipy)(N 3 ) 2 ] (bipy = 2,2‘-bipyridine), has been synthesized and characterized. Its crystal structure has been solved at room temperature. The complex crystallizes in the triclinic P 1̄ space group,…
According to the Heisenberg uncertainty principle of quantum mechanics, particles which are localized in space by a bounding potential must have a finite distribution of momenta. This leads, even in the lowest-possible energy state, to vibrations, and thus, to the so-called zero-point energy. For chemically bound hydr…
X-ray diffraction, thermoconductivity and nuclear magnetic resonance experiments have been carried out in order to study the diffusion mechanism of N atoms in the lattice. These experiments reveal that a small number of N atoms which enter the lattice, but do not occupy the octahedral interstitial sites, are mobile at…
We have studied the oxidation of single crystalline Cr(110) films prepared by molecular beam epitaxy (MBE) in the temperature range from 400 K to 700 K. Epitaxial α-Cr 2 O 3 layers in [0001] orientation are formed over the whole temperature range. We monitor the oxidation by X-ray reflectivity measurements providing i…
We have observed ultraviolet upconversion fluorescence from the D3/24 and P3/22 levels of Nd3+ in fluoroindate glass under infrared pumping. It was found that the excitation of a large population in the F3/24 metastable level allows to achieve strong upconversion emissions at 354 and 382 nm. A simple rate equation mod…
Abstract The synthesis of three novel pyrazole‐containing complexing acids, N,N,N′,N ′‐{2, 6‐bis[3‐(aminomethyl)pyrazol‐1‐yl]‐4‐methoxypyridine}tetrakis(acetic acid)( 1 ), N,N,N ′, N ′‐{2, 6‐bis[3‐(aminomethyl)pyrazol‐1‐yl]pyrazine}‐tetrakis(acetic acid) ( 2 ), and N,N,N ′, N ′‐{6, 6′‐bis[3‐(aminomethyl)pyrazol‐1‐yl]‐…
The influence of ambient temperature and applied electric field on the electrical properties of high resistivity (1–30 kΩ cm), semi-insulating (>100 kΩ cm), and insulating (1011–1012 Ω cm) single-crystal 6H–SiC is reported. Current–voltage (I–V) characteristics of lateral metal-semiconductor-metal test structur…
The rheology of solvent-filled polymer brushes under steady and oscillatory shear is studied by Brownian dynamics simulation. The flow field is solved self-consistently with the polymer dynamics. We find that under steady flow the brushes are shear thinning in both normal forces and shear viscosity. During oscillatory…
We developed a dual frequency cholesteric light shutter which utilizes a cholesteric liquid crystal; the dielectric anisotropy of the material changes from positive to negative when the frequency of applied voltage is increased. The shutters are switched to the transparent homeotropic texture by low frequency voltages…
We present the results of comparative inelastic neutron scattering measurements of both amorphous and crystalline silicates. We demonstrate the presence of floppy modes in amorphous silica and potassium disilicate over the energy scale 0--5 meV. A peak is also observed at 5 meV in amorphous silica, which is traditiona…
The critical current of a thin film of the high- ${T}_{c}$ superconductor ${\mathrm{DyBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$, when incorporated in a heterostructure in which it is separated from a ferromagnetic underlayer of ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_{3}$ by an undoped ultrathin ${\math…
Magnetic entropy change larger than that of gadolinium has been observed in polycrystalline of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ ( $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.2$ and 0.33) perovskite-type manganese oxide. The large magnetic entropy change produced by the a…
We propose a model in which the time dependence of the photoluminescence intensity of a single nanosize quantum dot under cw excitation conditions shows a sequence of ``on'' and ``off'' periods similar to a random telegraph signal. In our model the off periods are the times when the dot is ionized and the luminescence…