113 research outputs found
How other Europeans assess the dangers of leaving the EU
Public support for the EU rose after the referendum, while Jean-Claude Juncker has painted a starry picture of the Union's prospects without Britain. In effect, writes Catherine E De Vries, the UK is a guinea pig for Eurosceptics on the rest of the continent. Consequently, national leaders have every incentive to make Brexit as arduous as possible for the UK. Parties like the AfD are watching
Th<sub>3</sub>[Th<sub>6</sub>(OH)<sub>4</sub>O<sub>4</sub>(H<sub>2</sub>O)<sub>6</sub>](SO<sub>4</sub>)<sub>12</sub>(H<sub>2</sub>O)<sub>13</sub>: A Self-Assembled Microporous Open-Framework Thorium Sulfate
A neutral-framework thorium oxohydroxosulfate
hydrate has been
isolated from aqueous solution. This microporous structure, which
self-assembles without a templating agent, is built from [Th<sub>6</sub>(OH)<sub>4</sub>O<sub>4</sub>(H<sub>2</sub>O)<sub>6</sub>]<sup>12+</sup> hexamers and thoriumĀ(IV) monomers linked through bridging sulfates.
Solution conditions were chosen to enable an active competition between
sulfate and hydroxide for thorium coordination. Synthetic requirements
are discussed for this rare example of a thoriumĀ(IV) polynuclear complex
containing mixed oxo-, hydroxo-, and sulfato-bridging moieties
A robust seismic phase unwrapping method
Primary GO categorisation, KEGG and BIOCARTA pathway analyses (Target gene (cis, trans and co-expression) of lncRNAs were predicted based on differentially expressed mRNAs in IBDV-stimulated chicken DCs). (XLSX 335 kb
Tailoring the Olefin Selectivity in Catalytic Oxidative Dehydrogenation of Light Alkane by the Isolation Strategy
Olefins are important building blocks
that have been
extensively
used to produce diverse consumer products in petrochemical industry.
Owing to the requirement of low-carbon-footprint processes and the
increasing use of light alkanes sourced from shale gas, an environmentally
friendly and economic route alternative to the state-of-the-art steam
cracking of crude oil has been investigated for olefin production.
The oxidative dehydrogenation (ODH) of alkanes to olefins has attracted
wide attention due to the absence of thermodynamic limitations and
coke formation. However, excessive oxidation of olefin is prone to
occur in this process. Developing a suitable ODH catalyst with high
performance, particularly with enhanced selectivity, is more and more
urgent but still remains a challenge. In this Review, we talk about
the representative currently developed isolation strategies to optimize
the selectivity of olefins via the ODH process, particularly for the
conversion of ethane to ethylene, which include the dispersion regulation
of metal oxide, the isolation of metal and nonmetal sites, the construction
of dual functional sites to isolate dehydrogenation and oxidation
steps, and the adoption of selective oxygen species with the promotion
of soft oxidants as reactants. Furthermore, the mechanistic aspects
about the activation of ethane and the participation of oxygen species
for tailoring the selectivity are then classified and discussed in
detail. Finally, the perspectives and the emerging technologies for
the ODH process are listed and evaluated
Exploring Second-Order Nonlinear Optical Properties and Switching Ability of a Series of Dithienylethene-Containing, Cyclometalated Platinum Complexes: A Theoretical Investigation
The second-order nonlinear optical
(NLO) properties of a series of dithienylethene- (DTE-) containing
PtĀ(II) complexes have been investigated by density functional theory
calculations. The first hyperpolarizabilities Ī² of studied systems
can be greatly enhanced by simple ligand substitutions. Because of
the nature of DTE units, the Ī² values also can be varied by
the use of lights in the studied systems. The highest Ī² difference
between photoisomers can over 1000 Ć 10<sup>ā30</sup> esu,
with the contrast around five times. Thus, the studied systems can
act as effective photoswitchable second-order NLO materials. The time-dependent
density functional theory calculations revealed that the charge transfer
patterns of studied systems have special characters compared to other
reported DTE-containing NLO switched chromogens, the DTE units mainly
act as electron-donors in studied systems, and the variation of Ī²
can be viewed as alternation of donor abilities of DTE units; thus,
our work also proposed a new mechanism for designing photoswitched
NLO multifunctional materials
Influence of Countercation Hydration Enthalpies on the Formation of Molecular Complexes: A ThoriumāNitrate Example
The influence of
countercations (A<sup><i>n</i>+</sup>) in directing the
composition of monomeric metalāligand (ML)
complexes that precipitate from solution are often overlooked despite
the wide usage of A<sup><i>n</i>+</sup> in materials synthesis.
Herein, we describe a correlation between the composition of ML complexes
and A<sup>+</sup> hydration enthalpies found for two related series
of thorium (Th)ānitrate molecular compounds obtained by evaporating
acidic aqueous Thānitrate solutions in the presence of A<sup>+</sup> counterions. Analyses of their chemical composition and solid-state
structures demonstrate that A<sup>+</sup> not only affects the overall
solid-state packing of the Thānitrato complexes but also influences
the composition of the Thānitrato monomeric anions themselves.
Trends in composition and structure are found to correlate with A<sup>+</sup> hydration enthalpies, such that the A<sup>+</sup> with smaller
hydration enthalpies associate with less hydrated and more anionic
Thānitrato complexes. This perspective, broader than the general
assumption of size and charge as the dominant influence of A<sup><i>n</i>+</sup>, opens a new avenue for the design and synthesis
of targeted metalāligand complexes
Identifying Size Effects of Pt as Single Atoms and Nanoparticles Supported on FeO<sub><i>x</i></sub> for the Water-Gas Shift Reaction
Identification
of size effects at an atomic level is essential
for designing high-performance metal-based catalysts. Here, the performance
of a series of FeO<sub><i>x</i></sub>-supported Pt catalysts
with Pt as nanoparticles (Pt-NP) or single atoms (Pt-SAC) are compared
for the low-temperature water-gas shift (WGS) reaction. A variety
of characterization methods such as adsorption microcalorimetry, H<sub>2</sub>-TPR, in situ DRIFTS, and transient analysis of product tests
were used to demonstrate that Pt nanoparticles exhibit much higher
adsorption strength of CO; the adsorbed CO reacts with the OH groups,
which are generated from activated H<sub>2</sub>O, to form intermediate
formates that subsequently decompose to produce CO<sub>2</sub> and
H<sub>2</sub> simultaneously. On the other hand, Pt single atoms promote
the formation of oxygen vacancies on FeO<sub><i>x</i></sub> which dissociate H<sub>2</sub>O to H<sub>2</sub> and adsorbed O
that then combines with the weakly adsorbed CO on these Pt sites to
produce CO<sub>2</sub>. The activation energy for the WGS reaction
decreases with the downsizing of Pt species, and Pt-SAC possesses
the lowest value of 33 kJ/mol. As a result, Pt-SAC exhibits 1 order
of magnitude higher specific activity in comparison to Pt-NP. With
a loading of only 0.05 wt % the Pt-SAC can achieve ā¼65% CO
conversion at 300 Ā°C, representing one of the most active catalysts
reported so far
Thermochromism, the Alexandrite Effect, and Dynamic JahnāTeller Distortions in Ho<sub>2</sub>Cu(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>
A 3dā4f
heterobimetallic material with mixed anions, Ho<sub>2</sub>CuĀ(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>, has been prepared
under hydrothermal conditions. Ho<sub>2</sub>CuĀ(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub> exhibits both thermochromism
and the Alexandrite effect. Variable temperature single crystal X-ray
diffraction and UVāvisāNIR spectroscopy reveal that
changes in the Cu<sup>II</sup> coordination geometry result in negative
thermal expansion of axial CuāO bonds that plays a role in
the thermochromic transition of Ho<sub>2</sub>CuĀ(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>. Magnetic studies reveal
an effective magnetic moment of 14.97 Ī¼B. which has a good agreement
with the calculated value of 15.09 Ī¼B
Challenges in the Search for Magnetic Coupling in 3d/4f Materials: Syntheses, Structures, and Magnetic Properties of the Lanthanide Copper Heterobimetallic Compounds, RE<sub>2</sub>Cu(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>
Twelve new lanthanide copper heterobimetallic
compounds, RE<sub>2</sub>CuĀ(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub> (RE = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and
Lu), with two
different structural topologies, have been prepared by hydrothermal
treatment. Both structure types crystallize in the triclinic space
group, <i>P</i>1Ģ
, but the unit cell parameters and
structures are quite different. The earlier RE<sub>2</sub>CuĀ(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub> (RE = Y, Nd, Sm,
Eu, Gd, Tb, Dy, Ho, Er, and Tm) share a common structural motif consisting
of edge-sharing LnO<sub>8</sub> chains and [CuĀ(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>]<sup>6ā</sup> units. The
later lanthanide version (Yb and Lu) is composed of edge-sharing LnO<sub>7</sub> dimers bridged by similar [CuĀ(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>]<sup>6ā</sup> units. The change
in the structure type can be attributed to the decreasing ionic radii
of the lanthanides. The compounds containing RE<sup>3+</sup> ions
with diamagnetic ground states (Y<sup>3+</sup> and Eu<sup>3+</sup>) exhibit antiferromagnetic ordering at 12.5 K and 15 K, respectively,
owing to the magnetic exchange between Cu<sup>2+</sup> moments. No
magnetic phase transition was observed in all the other phases. The
lack of magnetic ordering is attributed to the competing magnetic
interactions caused by the presence of paramagnetic RE<sup>3+</sup> ions. The magnetism data suggests that substantial 3dā4f
coupling only occurs in the Yb analogue
Cuprous Iodide Pseudopolymorphs Based on Imidazole Ligand and Their Luminescence Thermochromism
Two
cuprous iodide pseudopolymorphs, formulated as [(Cu<sub>4</sub>I<sub>4</sub>)Ā(MBI)<sub>2</sub>]<sub>ā</sub> (MBI = 1,1ā²-methylene-bisĀ(imidazole))
with an irregular cubane-like Cu<sub>4</sub>I<sub>4</sub> cluster
as tetrahedrally coordinated secondary building unit and imidazole
derivative as bridging ligand, have been synthesized and characterized
by single-crystal X-ray diffraction analysis. Both of two compounds
only exhibited a single broad low-energy cluster-centered (<sup>3</sup>CC) triplet emission band between room temperature and 77 K. Of particular
interest, these two Cu<sub>4</sub>I<sub>4</sub>-imidazole pseudopolymorphs
still displayed thermochromic luminescence originating from a red
shift of such tunable single cluster-centered triplet emission, being
different from that observed in the previously reported Cu<sub>4</sub>I<sub>4</sub>-pyridine system by balancing temperature-dependent
multiple emissions (high-energy and low-energy) derived from their
energetically distinct triplet states
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