40 research outputs found
Additional file 1 of Quantitative proteomics identified circulating biomarkers in lung adenocarcinoma diagnosis
Additional file 1: Table S1. Differentially expressed proteins identified in plasma samples
Choses et gens de la Martinique, ce que la Martinique demande à la France / André Delaunay-Belleville
Contient une table des matièresAvec mode text
Unravelling Thiol’s Role in Directing Asymmetric Growth of Au Nanorod–Au Nanoparticle Dimers
Asymmetric nanocrystals
have practical significance in nanotechnologies but present fundamental
synthetic challenges. Thiol ligands have proven effective in breaking
the symmetric growth of metallic nanocrystals but their exact roles
in the synthesis remain elusive. Here, we synthesized an unprecedented
Au nanorod–Au nanoparticle (AuNR–AuNP) dimer structure
with the assistance of a thiol ligand. On the basis of our experimental
observations, we unraveled for the first time that the thiol could
cause an inhomogeneous distribution of surface strains on the seed
crystals as well as a modulated reduction rate of metal precursors,
which jointly induced the asymmetric growth of monometallic dimers
Atomic Resolution Imaging of Nanoscale Structural Ordering in a Complex Metal Oxide Catalyst
The determination of the atomic structure of a functional
material
is crucial to understanding its “structure-to-property”
relationship (e.g., the active sites in a catalyst), which is however
challenging if the structure possesses complex inhomogeneities. Here,
we report an atomic structure study of an important MoVTeO complex
metal oxide catalyst that is potentially useful for the industrially
relevant propane-based BP/SOHIO process. We combined aberration-corrected
scanning transmission electron microscopy with synchrotron powder
X-ray crystallography to explore the structure at both nanoscopic
and macroscopic scales. At the nanoscopic scale, this material exhibits
structural and compositional order within nanosized “domains”,
while the domains show disordered distribution at the macroscopic
scale. We proposed that the intradomain compositional ordering and
the interdomain electric dipolar interaction synergistically induce
the displacement of Te atoms in the Mo–V–O channels,
which determines the geometry of the multifunctional metal oxo-active
sites
Cu-TDPAT, an <i>rht</i>-Type Dual-Functional Metal–Organic Framework Offering Significant Potential for Use in H<sub>2</sub> and Natural Gas Purification Processes Operating at High Pressures
The separations of CO<sub>2</sub>/CO/CH<sub>4</sub>/H<sub>2</sub>, CO<sub>2</sub>/H<sub>2</sub>, CH<sub>4</sub>/H<sub>2</sub>, and
CO<sub>2</sub>/CH<sub>4</sub> mixtures at pressures ranging to 7 MPa
are important in a variety of contexts, including H<sub>2</sub> production,
natural gas purification, and fuel-gas processing. The primary objective
of this study is to demonstrate the selective adsorption potential
of an <i>rht</i>-type metal–organic framework [Cu<sub>3</sub>(TDPAT)Â(H<sub>2</sub>O)<sub>3</sub>]·10H<sub>2</sub>O·5DMA
(Cu-TDPAT), possessing a high density of both open metal sites and
Lewis basic sites. Experimental high pressure pure component isotherm
data for CO<sub>2</sub>, CO, CH<sub>4</sub>, and H<sub>2</sub> are
combined with the Ideal Adsorbed Solution Theory (IAST) for estimation
of mixture adsorption equilibrium. The separation performance of Cu-TDPAT
is compared with four other microporous materials, specifically chosen
in order to span a wide range of physicochemical characteristics:
MgMOF-74, MIL-101, LTA-5A, and NaX. For all mixtures investigated,
the capacity of Cu-TDPAT to produce the desired product, H<sub>2</sub> or CH<sub>4</sub>, satisfying stringent purity requirements, in
a fixed bed operating at pressures exceeding about 4 MPa, is either
comparable to, or exceeds, that of other materials
Investigating the Influence of Mesoporosity in Zeolite Beta on Its Catalytic Performance for the Conversion of Methanol to Hydrocarbons
Hierarchically porous zeolite Beta
(Beta-MS) synthesized by a soft-templating
method contains remarkable intracrystalline mesoporosity, which reduces
the diffusion length in zeolite channels down to several nanometers
and alters the distribution of Al among distinct crystallographic
sites. When it was used as a catalyst for the conversion of methanol
to hydrocarbons (MTH) at 330 °C, Beta-MS exhibited a 2.7-fold
larger conversion capacity, a 2.0-fold faster reaction rate, and a
remarkably longer lifetime in comparison to conventional zeolite beta
(Beta-C). The superior catalytic performance of Beta-MS is attributed
to its hierarchical structure, which offers full accessibility to
all catalytically active sites. In contrast, Beta-C was easily deactivated
because a layer of coke quickly deposited on the outer surfaces of
the catalyst crystals, impeding access to interior active sites. This
difference is clearly demonstrated by using electron microscopy combined
with electron energy loss spectroscopy to probe the distribution of
coke in the deactivated catalysts. At both low and high conversions,
ranging from 20% to 100%, Beta-MS gave higher selectivity toward higher
aliphatics (C<sub>4</sub>–C<sub>7</sub>) but lower ethene selectivity
in comparison to Beta-C. Therefore, we conclude that a hierarchical
structure decreases the residence time of methylbenzenes in zeolite
micropores, disfavoring the propagation of the aromatic-based catalytic
cycle. This conclusion is consistent with a recent report on ZSM-5
and is also strongly supported by our analysis of soluble coke species
residing in the catalysts. Moreover, we identified an oxygen-containing
compound, 4-methylbenzaldehyde, in the coke, which has not been observed
in the MTH reaction before
Synthesis and Gas Transport Properties of Hydroxyl-Functionalized Polyimides with Intrinsic Microporosity
A newly designed diamine monomer, 3,3,3′,3′-tetramethyl-1,1′-spirobisindane-5,5′-diamino-6,6′-diol,
was successfully used to synthesize two types of polyimides for membrane-based
gas separation applications. The novel polymers integrate significant
microporosity and polar hydroxyl groups, showing the combined features
of polymers of intrinsic microporosity (PIMs) and functional polyimides
(PIs). They possess high thermal stability, good solubility, and easy
processability for membrane fabrication; the resulting membranes exhibit
good permeability owing to the intrinsic microporosity introduced
by the highly contorted PIM segments as well as high CO<sub>2</sub>/CH<sub>4</sub> selectivity that arises from the hydroxyl groups.
The membranes show CO<sub>2</sub>/CH<sub>4</sub> selectivities of
>20 when tested with a 1:1 CO<sub>2</sub>/CH<sub>4</sub> mixture
for
feed pressures up to 50 bar. In addition, the incorporation of hydroxyl
groups and microporosity in the polymers enhances their affinity to
water, leading to remarkable water sorption capacities of up to 22
wt % at 35 °C and 95% relative humidity
Chiral Gold Nanowires with Boerdijk–Coxeter–Bernal Structure
A Boerdijk–Coxeter–Bernal
(BCB) helix is made of
linearly stacked regular tetrahedra (<i>tetrahelix</i>).
As such, it is chiral without nontrivial translational or rotational
symmetries. We demonstrate here an example of the chiral BCB structure
made of totally symmetrical gold atoms, created in nanowires by direct
chemical synthesis. Detailed study by high-resolution electron microscopy
illustrates their elegant chiral structure and the unique one-dimensional
“pseudo-periodicity”. The BCB-type atomic packing mode
is proposed to be a result of the competition and compromise between
the lattice and surface energy
Strong Metal–Support Interactions Achieved by Hydroxide-to-Oxide Support Transformation for Preparation of Sinter-Resistant Gold Nanoparticle Catalysts
The
strong metal–support interactions (SMSI) are well-known
but crucial for preparation of supported metal nanoparticle catalysts,
which generally occur by reduction and oxidation under harsh conditions.
Here, we delineate the example of constructing SMSI without reduction
and oxidation, where the key is to employ a hydroxide-to-oxide support
transformation. The covering of Au nanoparticles by oxides, electronic
interaction, and changes in CO adsorption tests of the catalyst are
identical to those of the classic SMSI. Owing to the SMSI with oxide
barriers on the Au nanoparticles, the supported Au catalysts are sintering-resistant
at high temperatures, which benefit long-life reactions, outperforming
the conventional supported catalysts
Site-Specific Growth of Au–Pd Alloy Horns on Au Nanorods: A Platform for Highly Sensitive Monitoring of Catalytic Reactions by Surface Enhancement Raman Spectroscopy
Surface-enhanced Raman scattering (SERS) is a highly sensitive
probe for molecular detection. The aim of this study was to develop
an efficient platform for investigating the kinetics of catalytic
reactions with SERS. To achieve this, we synthesized a novel Au–Pd
bimetallic nanostructure (HIF-AuNR@AuPd) through site-specific epitaxial
growth of Au–Pd alloy horns as catalytic sites at the ends
of Au nanorods. Using high-resolution electron microscopy and tomography,
we successfully reconstructed the complex three-dimensional morphology
of HIF-AuNR@AuPd and identified that the horns are bound with high-index
{11<i>l</i>} (0.25 < <i>l</i> < 0.43) facets.
With an electron beam probe, we visualized the distribution of surface
plasmon over the HIF-AuNR@AuPd nanorods, finding that strong longitudinal
surface plasmon resonance concentrated at the rod ends. This unique
crystal morphology led to the coupling of high catalytic activity
with a strong SERS effect at the rod ends, making HIF-AuNR@AuPd an
excellent bifunctional platform for <i>in situ</i> monitoring
of surface catalytic reactions. Using the hydrogenation of 4-nitrothiophenol
as a model reaction, we demonstrated that its first-order reaction
kinetics could be accurately determined from this platform. Moreover,
we clearly identified the superior catalytic activity of the rod ends
relative to that of the rod bodies, owing to the different SERS activities
at the two positions. In comparison with other reported Au–Pd
bimetallic nanostructures, HIF-AuNR@AuPd offered both higher catalytic
activity and greater detection sensitivity