37 research outputs found
One-Pot Synthesis of Water-Swellable MgâAl Layered Double Hydroxides and Graphene Oxide Nanocomposites for Efficient Removal of As(V) from Aqueous Solutions
In this Article,
we report a remarkably simple and efficient method for the preparation
of layered double hydroxides and graphene oxide (LDHs/GO) nanocomposites
with varying GO amounts via a hydrothermal process. The graphene nature
in the resulting LDHs/GO nanocomposites was confirmed by X-ray diffraction
(XRD), Fourier transformed infrared (FTIR) spectroscopy, field-emission
scanning electron microscopy (FE-SEM), transmission electron microscopy
(TEM), N<sub>2</sub> adsorption-desorption, and X-ray photoelectron
spectroscopy (XPS). The LDHs/GO nanocomposites exhibited swelling
behavior in water and forming a gel. The adsorption performance of
the LDHs/GO nanocomposites was evaluated for the removal of arsenate
(AsÂ(V)) from aqueous solutions, and the results showed that the ratio
of GO to LDHs in the nanocomposites significantly affected the adsorption
capacity. Higher and lower amounts of GO in LDHs/GO nanocomposites
showed lower adsorption capacity of AsÂ(V). A maximum adsorption capacity
of 183.11 mg/g (2.44 mmol/g) was achieved on the LDHs/GO containing
6.0% GO due to the higher BrunauerâEmmettâTeller (BET)
surface area than other samples. Owing to their high uptake capability
of AsÂ(V), water-swellable LDHs/GO nanocomposites are expected to have
potential applications as adsorbents for AsÂ(V) polluted water cleanup
Big Groundwater Data Sets Reveal Possible Rare Contamination Amid Otherwise Improved Water Quality for Some Analytes in a Region of Marcellus Shale Development
Eleven thousand groundwater samples
collected in the 2010s in an
area of Marcellus shale-gas development are analyzed to assess spatial
and temporal patterns of water quality. Using a new data mining technique,
we confirm previous observations that methane concentrations in groundwater
tend to be naturally elevated in valleys and near faults, but we also
show that methane is also more concentrated near an anticline. Data
mining also highlights waters with elevated methane that are not otherwise
explained by geologic features. These slightly elevated concentrations
occur near 7 out of the 1,385 shale-gas wells and near some conventional
gas wells in the study area. For ten analytes for which uncensored
data are abundant in this 3,000 km<sup>2</sup> rural region, concentrations
are unchanged or improved as compared to samples analyzed prior to
1990. Specifically, TDS, Fe, Mn, sulfate, and pH show small but statistically
significant improvement, and As, Pb, Ba, Cl, and Na show no change.
Evidence from this rural area could document improved groundwater
quality caused by decreased acid rain (pH, sulfate) since the imposition
of the Clean Air Act or decreased steel production (Fe, Mn). Such
improvements have not been reported in groundwater in more developed
areas of the U.S
Additional file 2: Figure S2. of Extracellular histones are clinically relevant mediators in the pathogenesis of acute respiratory distress syndrome
Extracellular histones among ARDS patients with different etiologies. (TIFF 58ĂÂ kb
Anisotropic Photophysical Properties of Highly Aligned Crystalline Structures of a Bulky Substituted Poly(thiophene)
The photophysical properties of a
phenyl-substituted polyÂ(thiophene),
polyÂ(3-(2,5-dioctylphenyl)Âthiophene) (PDOPT), were studied as a function
of polarization and degree of orientation of the crystalline structure.
Under well-chosen controlled conditions, large-sized spherulitic crystals
of PDOPT were successfully prepared from the melt. From polarized
optical microscopy and X-ray diffraction, the molecular orientation
of PDOPT within the spherulite was determined, indicating that the
fastest growth direction of the spherulite was the <i>a</i>-axis. This implied that crystallization of PDOPT was directed by
the packing of the side chains rather than the backbones, which are
significantly separated. As the crystalline lamellae were all radially
oriented, the local absorbance strongly depended on the polarization
of the incoming light. Compared to randomly oriented crystals in a
quenched and thus rapidly crystallized sample, PDOPT spherulites displayed
red-shifted absorption and emission spectra, combined with a reduced
photoluminescence quantum yield. Even for these markedly separated
polymer backbones (1.47 nm), the reduced photoluminescence suggests
an enhancement of interchain interactions of highly ordered bulky
substituted polythiophene induced by crystallization
High-strength Alâ5Mg<sub>2</sub>Siâ2Mgâ2Fe alloy with extremely high Fe content for green industrial application through additive manufacturing
Achieving superior mechanical properties of Al alloys with high content of Fe impurities is very challenging. Here, a feasible method was applied to accommodate high Fe content (âŒ2.2 wt.%) and obtain superior strength in an Alâ5Mg2Siâ2Mgâ2Fe alloy by using additive manufacturing. Heterogeneous distribution of Fe, including a high number density of α-Al12(Fe,Mn)3Si particles distributed at the melting pool boundary and excessive Fe segregated along the cell boundaries that divided by Mg2Si eutectics, was verified as the beneficial factor for the alloy design and strength enhancement. In addition to the heterogeneous grains that contain fine cells, the interactions between dislocations and coherent Mg2Si eutectics and the α-Al12(Fe,Mn)3Si particles played an important role in improving the mechanical properties. This work represents a breakthrough in recycling high-strength Al alloys with extremely high Fe doping for green industrial application through additive manufacturing.</p
Integration of a Superparamagnetic Scaffold and Magnetic Field To Enhance the Wound-Healing Phenotype of Fibroblasts
Most
of the existing scaffolds for guiding tissue regeneration do not provide
direct mechanical stimulation to the cells grown on them. In this
work, we used nanofibrous superparamagnetic scaffolds with applied
magnetic fields to build a âdynamicâ scaffold platform
and investigated the modulating effects of this platform on the phenotypes
of fibroblasts. The results of enzyme-linked immunosorbent and transwell
assays indicated that fibroblasts cultivated in this platform secreted
significantly higher type I collagen, vascular endothelial growth
factor A, and transforming growth factor-ÎČ1 and did so in a
time-dependent manner. At the same time, they produced fewer pro-inflammatory
cytokines, including interleukin-1ÎČ and monocyte chemoattractant
protein-1; this, in turn, accelerated the osteogenesis of preosteoblasts
with the help of increased basic fibroblast growth factor as well
as balanced extracellular matrix components. Mechanistic studies revealed
that the platform modulated the phenotypic polarization of fibroblasts
through the activation of components of integrin, focal adhesion kinase,
and extracellular signal-regulated kinase signaling pathways and the
inhibition of the activation of Toll-like receptor-4 and nuclear factor ÎșB.
Overall, the platform promoted the wound-healing phenotype of fibroblasts,
which would be of great benefit to the scaffold-guided tissue regeneration
Copper-Ion-Assisted Growth of Gold Nanorods in Seed-Mediated Growth: Significant Narrowing of Size Distribution via Tailoring Reactivity of Seeds
In the well-developed seed-mediated growth of gold nanorods
(GNRs), adding the proper amount of Cu<sup>2+</sup> ions in the growth
solution leads to significant narrowing in the size distribution of
the resultant GNRs, especially for those with shorter aspect ratios
(corresponding longitudinal surface plasmon resonance (LSPR) peaks
shorter than 750 nm). Cu<sup>2+</sup> ions were found to be able to
catalyze the oxidative etching of gold seeds by oxygen, thus mediating
subsequent growth kinetics of the GNRs. At proper Cu<sup>2+</sup> concentrations, the size distribution of the original seeds is greatly
narrowed via oxidative etching. The etched seeds are highly reactive
and grow quickly into desired GNRs with significantly improved size
distribution. A similar mechanism can be employed to tune the end
cap of the GNRs. Except for copper ions, no observable catalytic effect
is observed from other cations presumably due to their lower affinity
to oxygen. Considering the widespread use of seed-mediated growth
in the morphology-controlled synthesis of noble metal nanostructures,
the tailoring in seed reactivity we presented herein could be extended
to other systems
Handedness of Twisted Lamella in Banded Spherulite of Chiral Polylactides and Their Blends
Banded spherulite resulting from
lamellar twisting due to the imbalanced
stresses at opposite fold surfaces can be formed by isothermal crystallization
of chiral polylactide and its blends with polyÂ(ethylene glycol) (PEG).
Using a polarized light microscope, the handedness of the twisted
lamella in banded spherulite is determined. With the same growth axis
along the radial direction as evidenced by wide-angle X-ray diffraction
(WAXD) for isothermally crystallized samples at different temperatures,
the twisted lamellae of chiral polylactides (polyÂ(l-lactide)
(PLLA) and polyÂ(d-lactide) (PDLA)) display opposite handedness.
The split-type Cotton effect on the Cî»O stretching motion of
vibrational circular dichroism (VCD) spectra helps determine the helix
handedness (i.e., conformational chirality). The results indicate
that the conformational chirality can be defined by the molecular
chirality through intramolecular chiral interactions. Moreover, the
preferred sense of the lamellar twist in the banded spherulite corresponds
to the twisting direction identified by the CâOâC vibration
motion of VCD spectra, reflecting the role of intermolecular chiral
interactions in the packing of polylactide helices. Similar results
are obtained in the blends of chiral polylactides and polyÂ(ethylene
glycol) (PEG, a polymer compatible with polylactide), indicating that
the impact of chirality is intrinsic irrespective of the specific
crystallization conditions. In contrast to the chiral polylactides,
the spectrum of the crystalline stereocomplex that associates PLLA
and PDLA shows VCD silence. The spectroscopic results are in line
with the morphological observations. No banded spherulites are observed
in the stereocomplex crystallites due to the symmetric packing of
mirror L- and D-chain conformations in the fold surfaces and the crystallites
core