40 research outputs found
Controllable Stearic Acid Crystal Induced High Hydrophobicity on Cellulose Film Surface
A novel, highly hydrophobic cellulose composite film
(RCS) with biodegradability was fabricated via solvent-vaporized controllable
crystallization of stearic acid in the porous structure of cellulose
films (RC). The interface structure and properties of the composite
films were investigated with wide-angle X-ray diffraction (WAXD),
scanning electron microscopy (SEM), differential scanning calorimetry
(DSC), FT-IR, solid-state <sup>13</sup>C NMR, water uptake, tensile
testing, water contact angle, and biodegradation tests. The results
indicated that the RCS films exhibited high hydrophobicity (water
contact angle achieved to 145°), better mechanical properties
in the humid state and lower water uptake ratio than RC. Interestingly,
the stearic acid crystallization was induced by the pore wall of the
cellulose matrix to form a micronano binary structure, resulting in
a rough surface. The rough surface with a hierarchical structure containing
micronanospace on the RCS film surface could trap abundant air, leading
to the high hydrophobicity. Moreover, the RCS films were flexible,
biodegradable, and low-cost, showing potential applications in biodegradable
water-proof packaging
Homoleptic Chiral Benzamidinate Complexes of the Heavier Alkaline Earth Metals and the Divalent Lanthanides
Reaction of the chiral amidine <i>N</i>,<i>N</i>′-bisÂ(1-phenylÂethyl)Âbenzamidine
((<i>S</i>)-HPEBA), KCHÂ(SiMe<sub>3</sub>)<sub>2</sub>, and
MI<sub>2</sub> (M
= Ca, Sr, Ba) or LnI<sub>2</sub> (Ln = Eu, Yb) in a 2:2:1 stoichiometric
ratio resulted in the chiral homoleptic monomeric alkaline earth metal
compounds [CaÂ(PEBA)<sub>2</sub>Â(THF)<sub>2</sub>] (<b>1</b>) and [SrÂ(PEBA)<sub>2</sub>Â(THF)<sub>2</sub>] (<b>2</b>), the dimeric barium complex [BaÂ(PEBA)<sub>2</sub>]<sub>2</sub> (<b>3</b>), and the monomeric divalent lanthanide compounds
[EuÂ(PEBA)<sub>2</sub>Â(THF)<sub>2</sub>] (<b>4</b>), and
[YbÂ(PEBA)<sub>2</sub>Â(THF)<sub>2</sub>] (<b>5</b>). The
solid-state structures of all compounds were established by single-crystal
X-ray diffraction. Three different structures are observed in the
solid state. Compounds <b>1</b>, <b>2</b>, <b>4</b>, and <b>5</b> form distorted coordination octahedra. For the
alkaline earth element complexes <b>1</b> and <b>2</b>, the two THF molecules are located in a <i>trans</i>-position,
whereas, for the lanthanide compounds <b>4</b> and <b>5</b>, they are arranged in a <i>cis</i>-position. In contrast,
the barium complex <b>3</b> is dimeric with two amidinate ligands
in an unusual “side-on” bridging mode. All five complexes
were used as catalysts for hydrophosphination reactions of styrene
and substituted analogues
Hydrophobic Modification on Surface of Chitin Sponges for Highly Effective Separation of Oil
A highly hydrophobic and oleophilic
chitin sponge was synthesized, for the first time, via a freeze-dried
method and then by using a thermal chemical vapor deposition of methyltrichlorosilane
(MTCS) at different relative humidity. Fourier-transform infrared,
energy-dispersive X-ray spectra, and scanning electron microscopy
confirmed that the silanization occurred on the pore wall surface
of the chitin sponge. The MTCS-coated chitin sponge had interconnected
open-cell structures with the average pore size from 20 to 50 ÎĽm,
and the MTCS nanofilaments immobilized on the chitin matrix, leading
to the high hydrophobicity, as a result of the existence of a solid/air
composite rough surface. Cyclic compression test indicated that the
hydrophobic chitin sponges exhibited excellent elasticity and high
mechanical durability. The sponges could efficiently collect organics
both on the surface and bottom from the water with the highest 58
times of their own weight absorption capacities through the combination
of the particular wettability and great porosity. Furthermore, the
biodegradation kinetics of the chitin sponge forecasted that the chitin
could be completely biodegraded within 32 days by the microorganisms
in the soil. This work provided a new pathway to prepare the chitin-based
materials for highly effective removal of oil from water, showing
potential application in the pollutant remediation field
Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries
Compared with artificial vascular grafts, bottom-up tubular
cell
sheets (TCSs) without scaffolds have shown promise for patients with
cardiovascular disease. However, TCS therapy also faces the challenges
of lengthy maturation time, elaborate operation, and weak mechanical
strength. In this work, a structured small-diameter vascular graft
(SDVG), consisting of three layers of TCSs, with different cell types
and arrangements, was fabricated using layer-by-layer assembly of
naturally formed TCSs and further cell culture. To this end, a surface-patterned
collagen-coated cylindrical substrate was designed for the efficient
harvesting of naturally formed and well-aligned TCSs. The patterned
collagen (type I) layer facilitated the adhesion and orientation of
cells, and a continuous tubular cell monolayer was naturally formed
after approximately 4 days in cell culture. Biocompatible near-infrared
(NIR) light was used to trigger the photothermal phase transition
of the collagen coated on the cylindrical substrate to dissociate
the collagen layer. As a result, an intact TCS could be harvested
within a few minutes. These naturally formed and well-aligned TCSs
exhibited outstanding free-standing performance without rugosity,
facilitating their operability and practical application. A ring tensile
test showed that orientation was critical for improving the mechanical
properties of TCSs. The layer-by-layer assembly of SDVGs not only
is easy to manipulate and has a short preparation time but also overcomes
the bottleneck of forming a hierarchically structured vascular graft.
This approach shows promise for repairing damaged blood vessels
Deep-Learning Pipeline for Statistical Quantification of Amorphous Two-Dimensional Materials
Aberration-corrected transmission
electron microscopy enables imaging
of two-dimensional (2D) materials with atomic resolution. However,
dissecting the short-range-ordered structures in radiation-sensitive
and amorphous 2D materials remains a significant challenge due to
low atomic contrast and laborious manual evaluation. Here, we imaged
carbon-based 2D materials with strong contrast, which is enabled by
chromatic and spherical aberration correction at a low acceleration
voltage. By constructing a deep-learning pipeline, atomic registry
in amorphous 2D materials can be precisely determined, providing access
to a full spectrum of quantitative data sets, including bond length/angle
distribution, pair distribution function, and real-space polygon mapping.
Accurate segmentation of micropores and surface contamination, together
with robustness against background inhomogeneity, guaranteed the quantification
validity in complex experimental images. The automated image analysis
provides quantitative metrics with high efficiency and throughput,
which may shed light on the structural understanding of short-range-ordered
structures. In addition, the convolutional neural network can be readily
generalized to crystalline materials, allowing for automatic defect
identification and strain mapping
Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries
Compared with artificial vascular grafts, bottom-up tubular
cell
sheets (TCSs) without scaffolds have shown promise for patients with
cardiovascular disease. However, TCS therapy also faces the challenges
of lengthy maturation time, elaborate operation, and weak mechanical
strength. In this work, a structured small-diameter vascular graft
(SDVG), consisting of three layers of TCSs, with different cell types
and arrangements, was fabricated using layer-by-layer assembly of
naturally formed TCSs and further cell culture. To this end, a surface-patterned
collagen-coated cylindrical substrate was designed for the efficient
harvesting of naturally formed and well-aligned TCSs. The patterned
collagen (type I) layer facilitated the adhesion and orientation of
cells, and a continuous tubular cell monolayer was naturally formed
after approximately 4 days in cell culture. Biocompatible near-infrared
(NIR) light was used to trigger the photothermal phase transition
of the collagen coated on the cylindrical substrate to dissociate
the collagen layer. As a result, an intact TCS could be harvested
within a few minutes. These naturally formed and well-aligned TCSs
exhibited outstanding free-standing performance without rugosity,
facilitating their operability and practical application. A ring tensile
test showed that orientation was critical for improving the mechanical
properties of TCSs. The layer-by-layer assembly of SDVGs not only
is easy to manipulate and has a short preparation time but also overcomes
the bottleneck of forming a hierarchically structured vascular graft.
This approach shows promise for repairing damaged blood vessels
Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries
Compared with artificial vascular grafts, bottom-up tubular
cell
sheets (TCSs) without scaffolds have shown promise for patients with
cardiovascular disease. However, TCS therapy also faces the challenges
of lengthy maturation time, elaborate operation, and weak mechanical
strength. In this work, a structured small-diameter vascular graft
(SDVG), consisting of three layers of TCSs, with different cell types
and arrangements, was fabricated using layer-by-layer assembly of
naturally formed TCSs and further cell culture. To this end, a surface-patterned
collagen-coated cylindrical substrate was designed for the efficient
harvesting of naturally formed and well-aligned TCSs. The patterned
collagen (type I) layer facilitated the adhesion and orientation of
cells, and a continuous tubular cell monolayer was naturally formed
after approximately 4 days in cell culture. Biocompatible near-infrared
(NIR) light was used to trigger the photothermal phase transition
of the collagen coated on the cylindrical substrate to dissociate
the collagen layer. As a result, an intact TCS could be harvested
within a few minutes. These naturally formed and well-aligned TCSs
exhibited outstanding free-standing performance without rugosity,
facilitating their operability and practical application. A ring tensile
test showed that orientation was critical for improving the mechanical
properties of TCSs. The layer-by-layer assembly of SDVGs not only
is easy to manipulate and has a short preparation time but also overcomes
the bottleneck of forming a hierarchically structured vascular graft.
This approach shows promise for repairing damaged blood vessels
Monodisperse Antimony Nanocrystals for High-Rate Li-ion and Na-ion Battery Anodes: Nano versus Bulk
We report colloidal synthesis of
antimony (Sb) nanocrystals with
mean size tunable in the 10–20 nm range and with narrow size
distributions of 7–11%. In comparison to microcrystalline Sb,
10 and 20 nm Sb nanocrystals exhibit enhanced rate-capability and
higher cycling stability as anode materials in rechargeable Li-ion
and Na-ion batteries. All three particle sizes of Sb possess high
and similar Li-ion and Na-ion charge storage capacities of 580–640
mAh g<sup>–1</sup> at moderate charging/discharging current
densities of 0.5–1C (1C-rate is 660 mA g<sup>–1</sup>). At all C-rates (0.5–20C, e.g. current densities of 0.33–13.2
Ag<sup>1–</sup>), capacities of 20 nm Sb particles are systematically
better than for both 10 nm and bulk Sb. At 20C-rates, retention of
charge storage capacities by 10 and 20 nm Sb nanocrystals can reach
78–85% of the low-rate value, indicating that rate capability
of Sb nanostructures can be comparable to the best Li-ion intercalation
anodes and is so far unprecedented for Na-ion storage
Ternary Oxides in the TiO<sub>2</sub>–ZnO System as Efficient Electron-Transport Layers for Perovskite Solar Cells with Efficiency over 15%
Perovskite
solar cells, which utilize organometal–halide
perovskites as light-harvesting materials, have attracted great attention
due to their high power conversion efficiency (PCE) and potentially
low cost in fabrication. A compact layer of TiO<sub>2</sub> or ZnO
is generally applied as electron-transport layer (ETL) in a typical
perovskite solar cell. In this study, we explored ternary oxides in
the TiO<sub>2</sub>–ZnO system to find new materials for the
ETL. Compact layers of titanium zinc oxides were readily prepared
on the conducting substrate via spray pyrolysis method. The optical
band gap, valence band maximum and conduction band minimum of the
ternary oxides varied significantly with the ratio of Ti to Zn, surprisingly,
in a nonmonotonic way. When a zinc-rich ternary oxide was applied
as ETL for the device, a PCE of 15.10% was achieved, comparable to
that of the device using conventional TiO<sub>2</sub> ETL. Interestingly,
the perovskite layer deposited on the zinc-rich ternary oxide is stable,
in sharp contrast with that fabricated on a ZnO layer, which will
turn into PbI<sub>2</sub> readily when heated. These results indicate
that potentially new materials with better performance can be found
for ETL of perovskite solar cells in ternary oxides, which deserve
more exploration
A General Synthesis Strategy for Monodisperse Metallic and Metalloid Nanoparticles (In, Ga, Bi, Sb, Zn, Cu, Sn, and Their Alloys) via in Situ Formed Metal Long-Chain Amides
We report a facile one-pot synthesis
of highly monodisperse nanoparticles
(5–30 nm in diameter, 5–10% in standard size distribution)
of various metals and metalloids such as In, Sn, Bi, Sb, Ga, Cu, Zn,
and their alloys (Cu<sub>6</sub>Sn<sub>5</sub>, Cu<sub>2</sub>Sb,
Bi<sub><i>x</i></sub>Sb<sub>1–<i>x</i></sub>, etc.) using inexpensive commercial precursors. Several of these
metals and alloys had not been previously obtained in the form of
uniform nanoparticles. The proposed reaction mechanism has been elucidated
with multinuclear (<sup>1</sup>H, <sup>7</sup>Li, <sup>119</sup>Sn)
NMR spectroscopy combined with DFT and molecular dynamics simulations.
Metal chloride is reacted with long-chain primary or secondary amine
such as oleylamine and dioctylamine in the presence of a strong Brønsted
base that deprotonates the amine and thus promotes the formation of
metal long-chain amide. The in situ formed amide is then reduced or
thermally decomposed into corresponding metal nanoparticles. This
simple methodology eliminates elaborate preparation, storage, and
handling of highly reactive, moisture and oxygen sensitive molecular
precursors of these metals, while providing a compelling quality of
nanomaterials