Materials Literature
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Thick or thin? Hydrogen-bonded bis-urea forms two distinct rodlike assemblies—thick or thin filaments—in a variety of aromatic solvents. The stability of each is dependent on the size of the solvent molecules and a simple viscosity test (see figure) differentiates between them.
Branching out: Pd-catalyzed iterative triarylations of vinylboronate afford conjugated dendrimers with triarylethene branches (see picture) in a flexible and convergent manner. These highly branched dendrimers reveal good solubility in common organic solvents and exhibit high quantum yields of fluorescence, with the c…
A hierarchical structure of mesoporous−macroporous phosphated aluminum (oxyhydr)oxide (PAl) materials was prepared via a simple self-assembly process with the use of precursor aluminum sec -butoxide in a mixed solution of H 3 PO 4 and Na 2 HPO 4 . Direct phosphation resulted in the incorporation of phosphorus into the…
We report the resonant Raman spectra of individualized $(=debundled)$ single-walled carbon nanotubes (SWNTs) having diameters $d\ensuremath{\sim}0.8--1.3\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ subject to compression up to $10.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. Both SWNTs in water-surfactant dispersions as well…
A full range of ${\mathrm{SrRu}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}{\mathrm{O}}_{3}$ perovskite solid solutions $(0<x<1)$ has been prepared using high temperatures and pressures up to $10.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The structure changes from orthorhombic Pbnm at low $x$ through a previously unre…
We report experimental evidence for the charge-orbital ordering in magnetite below the Verwey transition temperature T(V). Measurements of O K-edge resonant x-ray scattering on magnetite reveal that the O 2p states in the vicinity of the Fermi level exhibit a charge-orbital ordering along the c axis with a spatial per…
The effect of specimen size on the uniaxial deformation response of planar single crystals and polycrystals is investigated using discrete dislocation plasticity. The dislocations are all of edge character and modelled as line singularities in a linear elastic material. The lattice resistance to dislocation motion, di…
Long-term memory aid: A one-handed helical poly(phenylacetylene) with positively charged pendant groups can serve as the template for supramolecular helical arrays of achiral porphyrins with opposite charges in acidic water. The supramolecular chirality induced in the porphyrin aggregates can be memorized even after t…
Natural inspiration: A lotus-leaf-like hierarchical structure is formed on a polycarbonate plate under mild conditions by successive plasticization and coagulation of the polymer surface. The resultant micron- and nanoscale rough structure, shown in the figure allows the common plastic to be superhydrophobic with a la…
Transition metal complexes involving the benzene-1,2-dithiol (L(2-)) and Sellmann's 3,5-di-tert-butylbenzene-1,2-dithiol(L(Bu 2-)) ligands have been studied by UV-vis, infrared (IR), and resonance Raman (rR) spectroscopies. Raman spectra were obtained in resonance with the intervalence charge transfer (IVCT) bands in…
In control: The secondary structure dependent self-assembly of β-peptides in solution proves that natural biopolymers are not unique in their highly structured conformational behavior. Stereochemically controlled secondary structural units of β-peptide strands and helices intrinsically self-associate into pleated-shee…
Two 2D supramolecular structures of macrocycle 1 and 1/C60 have been obtained on HOPG by self-assembly under ambient conditions and investigated by high-resolution STM. The monolayers of 1 are characterized by structures with perfect ordering over relatively large areas. In the case of 1/C60, the size of the macrocycl…
Tactics in polymerization: The molecular weight and the number, length, and placement of each stereoblock type in a polypropene were programmed to give discrete, multiblock, isotactic–atactic stereoblock microstructures. Several of these specifically designed stereoblock architectures give rise to thermoplastic elasto…
Single-molecule transistors provide a unique experimental tool to investigate the coupling between charge transport and the molecular degrees of freedom in individual molecules. One interesting class of molecules for such experiments are the single-molecule magnets, since the intramolecular exchange forces present in…
e have developed a simple process to obtain large magnetoresistance (MR) in perovskite manganite thin films by a combination of focused ion beam (FIB) milling and 120 keV H$_{2}^{+}$ ion implantation. Metal slits about 70 nm in width were printed by 30 kV focused Ga ion beam nanolithography on a 4 mm track, and the ma…
Investigations are reported into a range of defects causing partial discharge (PD) activity in high-voltage oil-insulated equipment. The aim is to explore the relationship between radiated ultra-high frequency (UHF) signals and electric charge in a PD current pulse for PD sources in oil insulation. Experiments are per…
We consider periodic domain structures which appear due to the magnetoelastic interaction if the antiferromagnetic crystal is attached to an elastic substrate. The peculiar behavior of such structures in an external magnetic field is discussed. In particular, we find the magnetic field dependence of the equilibrium pe…
We present a detailed discussion of extraordinary optoconductance (EOC). Experimental data was acquired via macroscopic metal-semiconductor hybrid structures composed of GaAs and In and subjected to illumination from an Ar ion laser. A drift diffusion model using the finite element method (FEM) provided a reasonable f…
We present a resonant x-ray scattering study of the octahedral tilt order between 50K and 310K in La_7/8Sr_1/8MnO_3. At the La L_II-edge the resonant (300) reflection probes cooperative tilts of the MnO_6-octahedra in this material, as verified by a model caclulation as well as a LDA+U study. The investigation of the…
Fundamental physical properties limiting the performance of spin field effect transistors are compared to those of ordinary (charge-based) field effect transistors. Instead of raising and lowering a barrier to current flow these spin transistors use static spin-selective barriers and gate control of spin relaxation. T…