1,220 research outputs found
Pulsed versus DC I-V characteristics of resistive manganites
We report on pulsed and DC I-V characteristics of polycrystalline samples of
three charge-ordered manganites, Pr_{2/3}Ca_{1/3}MnO_3, Pr_{1/2}Ca_{1/2}MnO_3,
Bi_{1/2}Sr_{1/2}MnO_3 and of a double-perovskite Sr_2MnReO_6, in a temperature
range where their ohmic resistivity obeys the Efros-Shklovskii variable range
hopping relation. For all samples, the DC I(V) exhibits at high currents
negative differential resistance and hysteresis, which mask a perfectly ohmic
or a moderately nonohmic conductivity obtained by pulsed measurements. This
demonstrates that the widely used DC I-V measurements are usually misleading.Comment: 6 pages, 4 figures. Accepted for publication to AP
Inter-grain tunneling in the half-metallic double-perovskites SrBB'O (BB'-- FeMo, FeRe, CrMo, CrW, CrRe
The zero-field conductivities () of the polycrystaline title
materials, are governed by inter-grain transport. In the majority of cases
their (T) can be described by the "fluctuation induced tunneling"
model. Analysis of the results in terms of this model reveals two remarkable
features: 1. For \emph{all} SrFeMoO samples of various microstructures,
the tunneling constant (barrier width inverse decay-length of the
wave-function) is 2, indicating the existence of an intrinsic insulating
boundary layer with a well defined electronic (and magnetic) structure. 2. The
tunneling constant for \emph{all} cold-pressed samples decreases linearly with
increasing magnetic-moment/formula-unit.Comment: 10 pages, 2 tables, 3 figure
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Selective photocatalytic CO reduction in water through anchoring of a molecular Ni catalyst on CdS nanocrystals
Photocatalytic conversion of CO into carbonaceous feedstock chemicals is a promising strategy to mitigate greenhouse gas emissions and simultaneously store solar energy in chemical form. Photocatalysts for this transformation are typically based on precious metals and operate in nonaqueous solvents to suppress competing H generation. In this work, we demonstrate selective visible-light-driven CO reduction in water using a synthetic photocatalyst system that is entirely free of precious metals. We present a series of self-assembled nickel terpyridine complexes as electrocatalysts for the reduction of CO to CO in organic media. Immobilization on CdS quantum dots allows these catalysts to be active in purely aqueous solution and photocatalytically reduce CO with >90% selectivity under UV-filtered simulated solar light irradiation (AM 1.5G, 100 mW cm, λ > 400 nm, pH 6.7, 25 °C). Correlation between catalyst immobilization efficiency and product selectivity shows that anchoring the molecular catalyst on the semiconductor surface is key in controlling the selectivity for CO reduction over H evolution in aqueous solution.Christian Doppler Research Association, OMV group, Isaac Newton Trust, the German Research Foundation, the World Premier International Research Center Initiative, MEXT, Japa
Plasmonic enhancement in BiVO4 photonic crystals for efficient water splitting.
Photo-electrochemical water splitting is a very promising and environmentally friendly route for the conversion of solar energy into hydrogen. However, the solar-to-H2 conversion efficiency is still very low due to rapid bulk recombination of charge carriers. Here, a photonic nano-architecture is developed to improve charge carrier generation and separation by manipulating and confining light absorption in a visible-light-active photoanode constructed from BiVO4 photonic crystal and plasmonic nanostructures. Synergistic effects of photonic crystal stop bands and plasmonic absorption are observed to operate in this photonic nanostructure. Within the scaffold of an inverse opal photonic crystal, the surface plasmon resonance is significantly enhanced by the photonic Bragg resonance. Nanophotonic photoanodes show AM 1.5 photocurrent densities of 3.1 ± 0.1 mA cm(-2) at 1.23 V versus RHE, which is among the highest for oxide-based photoanodes and over 4 times higher than the unstructured planar photoanode.UK Engineering and Physical Science Research Council. Grant Numbers: EP/H00338X/2, EP/G060649/1
European Community's Seventh Framework Programme. Grant Number: FP7/2007–2013
CARINHYPH project. Grant Number: 310184
Minstry of Science and Technology of Taiwan. Grant Number: 102-2218-E-006-014-MY2
Christian Doppler Research Association
OMV Group, a Marie Curie Intra-European Fellowship. Grant Number: FP7-PEOPLE-2011-IEF 298012
ERC. Grant Number: 320503This is the final published version currently under embargo. This will be updated once the publisher has granted a CC BY license
A simple approach to the correlation of rotovibrational states in four-atomic molecules
The problem of correlation between quantum states of four-atomic molecules in
different geometrical configurations is reviewed in detail. A general, still
simple rule is obtained which allows one to correlate states of a linear
four-atomic molecule with those of any kind of non-linear four-atomic molecule.Comment: 16 pages (+8 figures), Postscript (ready to print!
A Tool to Recover Scalar Time-Delay Systems from Experimental Time Series
We propose a method that is able to analyze chaotic time series, gained from
exp erimental data. The method allows to identify scalar time-delay systems. If
the dynamics of the system under investigation is governed by a scalar
time-delay differential equation of the form ,
the delay time and the functi on can be recovered. There are no
restrictions to the dimensionality of the chaotic attractor. The method turns
out to be insensitive to noise. We successfully apply the method to various
time series taken from a computer experiment and two different electronic
oscillators
Dichlorido[μ-10,21-dimethyl-2,7,13,18-tetraÂphenyl-3,6,14,17-tetraÂazaÂtricycloÂ[17.3.1.18,12]tetraÂcosa-1(23),2,6,8,10,12(24),13,17,19,21-decaÂene-23,24-diolato]dicopper(II) ethanol hemisolvate dihydrate
The dinuclear title complex, [Cu2(C46H38N4O2)Cl2]·0.5C2H5OH·2H2O, is located on crystallographic inversion centres with two half-molÂecules in the asymmetric unit. The two CuII atoms are coordinated by a hexaÂdentate dianionic ligand formed in situ from the condensation of two tridentate ligands by four imine N atoms and two bridging phenolate O atoms along with two Cl atoms at axial positions. The coordination geometry around the metal atoms is distorted square-pyramidal (Ï„ = 0.185 and 0.199). The non-bonding Cu⋯Cu distances are 2.9556 (12) and 2.9506 (12) Å in the two dimers. The packing is stabilized through solvent-mediated interÂmolecular O—H⋯O and O—H⋯Cl hydrogen bonds. The diamine chain of one of the dimers is disordered over two positions in a 0.680 (5):0.320 (5) ratio
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