7 research outputs found
Enhance Hydrogen Isotopes Separation by Alkali Earth Metal Dopant in Metal–Organic Framework
Kinetic quantum sieving (KQS) based on pore size and
chemical affinity
quantum sieving (CAQS) based on adsorption site are two routes of
porous materials to separate hydrogen isotope mixtures. Alkali earth
metals (Be, Mg, and Ca) were doped into UiO-67 to explore whether
these metal sites can promote H2/D2 separation.
Based on the zero-point energy and adsorption enthalpy calculated
by density functional theory calculations, the Be dopant shows better
H2/D2 separation performance than other alkali
earth metal dopants and unsaturated metal sites in metal–organic
frameworks based on CAQS. Orbital interaction strongly relates to
the chemical affinity and further influences the D2/H2 selectivity. Moreover, the predicted D2/H2 selectivity of Be-doped sites (49.4) at 77 K is even larger
than the best experimental result (26). Finally, the different dynamic
behaviors of H2 and D2 on Be-doped UiO-67 indicate
its strong H2/D2 separation performance via
KQS
Synthesis and Self-Assembly of Large-Area Cu Nanosheets and Their Application as an Aqueous Conductive Ink on Flexible Electronics
Large-area Cu nanosheets are synthesized
by a strategy of Cu nanocrystal
self-assembly, and then aqueous conductive Cu nanosheet ink is successfully
prepared for direct writing on the conductive circuits of flexible
electronics. The Cu nanocrystals, as building blocks, self-assemble
along the ⟨111⟩ direction and grow into large-area nanosheets
approximately 30–100 μm in diameter and a few hundred
nanometers in thickness. The laminar stackable patterns of the Cu
nanosheet circuits increase the contact area of the Cu nanosheets
and improve the stability of the conductor under stress, the result
being that the Cu nanosheet circuits display excellent conductive
performance during repeated folding and unfolding. Moreover, heterostructures
of Ag nanoparticle-coated Cu nanosheets are created to improve the
thermal stability of the nanosheet circuits at high temperatures
Vacuum-Dried Synthesis of Low-Density Hydrophobic Monolithic Bridged Silsesquioxane Aerogels for Oil/Water Separation: Effects of Acid Catalyst and Its Excellent Flexibility
Low-density
hydrophobic monolithic bridged silsesquioxane aerogels
were prepared by vacuum drying using terephthalaldehyde (TPAL) and
3-aminopropyl-triethoxysilane (APTES) as precursors and acetic acid
as catalyst. The effects of acid on the vacuum-dried synthesis of
bridged silsesquioxane aerogels were investigated. The results indicate
that the growth mechanism changes from cluster–cluster to monomer–cluster
when acid is added, which induces the formation of the low-density
monolithic aerogels with increased pore size. The methyltrimethoxysilane
(MTMS) co-precursor could endow the aerogels with good hydrophobicity.
The densities, pore structure, hydrophobicity, and mechanical properties
of the obtained bridged silsesquioxane aerogels were investigated
in detail. The results show that the monolithic aerogels possess low
density (0.071 g/cm<sup>3</sup>), high hydrophobicity (contact angle,
>140°), and excellent flexibility (Young’s modulus,
0.029
MPa). All of these characteristics make the hydrophobic aerogels competitive
candidates for oil/water separation
Vacuum-Dried Synthesis of Low-Density Hydrophobic Monolithic Bridged Silsesquioxane Aerogels for Oil/Water Separation: Effects of Acid Catalyst and Its Excellent Flexibility
Low-density
hydrophobic monolithic bridged silsesquioxane aerogels
were prepared by vacuum drying using terephthalaldehyde (TPAL) and
3-aminopropyl-triethoxysilane (APTES) as precursors and acetic acid
as catalyst. The effects of acid on the vacuum-dried synthesis of
bridged silsesquioxane aerogels were investigated. The results indicate
that the growth mechanism changes from cluster–cluster to monomer–cluster
when acid is added, which induces the formation of the low-density
monolithic aerogels with increased pore size. The methyltrimethoxysilane
(MTMS) co-precursor could endow the aerogels with good hydrophobicity.
The densities, pore structure, hydrophobicity, and mechanical properties
of the obtained bridged silsesquioxane aerogels were investigated
in detail. The results show that the monolithic aerogels possess low
density (0.071 g/cm<sup>3</sup>), high hydrophobicity (contact angle,
>140°), and excellent flexibility (Young’s modulus,
0.029
MPa). All of these characteristics make the hydrophobic aerogels competitive
candidates for oil/water separation
Synthesis of Heparin-Immobilized, Magnetically Addressable Cellulose Nanofibers for Biomedical Applications
Magnetically responsive
heparin-immobilized cellulose nanofiber
composites were synthesized by wet-wet electrospinning from a nonvolatile,
room-temperature ionic liquid (RTIL), 1-methyl-3-methylimidazolium
acetate ([EMIM]Â[Ac]), into an aqueous coagulation bath. Superparamagnetic
magnetite (Fe<sub>3</sub>O<sub>4</sub>) nanoparticles were incorporated
into the fibers to enable the manipulation of both dry and wet nanofiber
membranes with an external magnetic field. Three synthetic routes
were developed to prepare three distinct types of nanocomposite fibers:
cellulose-Fe<sub>3</sub>O<sub>4</sub>–heparin monofilament
fibers, cellulose-Fe<sub>3</sub>O<sub>4</sub>–heparin core–shell
fibers with heparin covalently immobilized on the fiber surface, and
cellulose -Fe<sub>3</sub>O<sub>4</sub> core–shell fibers with
heparin physically immobilized on the fiber surface. These nanocomposite
fibers were characterized by electron microscopy to confirm their
coaxial structure and the fiber dimensions (fiber diameter 0.2–2.0
μm with 0.1–1.1 μm core diameter). Thermogravimetric
analysis, liquid chromatography–mass spectrometry, Fourier
transform infrared and X-ray diffraction spectroscopy provided detailed
compositional analysis for these nanocomposite fibers, confirming
the presence of each component and the surface accessibility of the
heparin. The anticoagulant activity of immobilized heparin on the
nanocomposite fiber surfaces was evaluated and confirmed by antifactor
Xa and antifactor IIa assays
A Facile in Situ Self-Assembly Strategy for Large-Scale Fabrication of CHS@MOF Yolk/Shell Structure and Its Catalytic Application in a Flow System
A hierarchical
yolk/shell copper hydroxysulfates@MOF (CHS@MOF, where MOF = metal–organic
frameworks) structure was fabricated from a homogeneous yolk/shell
CHS template composed of an active shell and a stabilized core via
a facile self-template strategy at room temperature. The active shell
of the template served as the source of metal ion and was in situ
transformed into a well-defined MOF crystal shell, and the relatively
stabilized core retained its own nature during the formation of the
MOF shell. The strategy of in situ transformation of CHS shell to
MOF shell avoided the self-nucleation of MOF in the solution and complex
multistep procedures. Furthermore, a flow reaction system using CHS@MOF
as self-supported stationary-phase catalyst was developed, which demonstrated
excellent catalytic performance for aldehyde acetalization with ethanol,
and high yields and selectivities were achieved under mild conditions
Biodegradable and Bioactive PCL–PGS Core–Shell Fibers for Tissue Engineering
PolyÂ(glycerol sebacate)
(PGS) has increasingly become a desirable
biomaterial due to its elastic mechanical properties, biodegradability,
and biocompatibility. Here, we report microfibrous core–shell
mats of polycaprolactone (PCL)–PGS prepared using wet–wet
coaxial electrospinning. The anticoagulant heparin was immobilized
onto the surface of these electrospun fiber mats, and they were evaluated
for their chemical, mechanical, and biological properties. The core–shell
structure of PCL–PGS provided tunable degradation and mechanical
properties. The slowly degrading PCL provided structural integrity,
and the fast degrading PGS component increased fiber elasticity. Young’s
modulus of PCL–PGS ranged from 5.6 to 15.7 MPa. The ultimate
tensile stress ranged from 2.0 to 2.9 MPa, and these fibers showed
elongation from 290 to 900%. The addition of PGS and grafting of heparin
improved the attachment and proliferation of human umbilical vein
endothelial cells. Core–shell PCL–PGS fibers demonstrate
improved performance as three-dimensional fibrous mats for potential
tissue-engineering applications