1,748,100 research outputs found
Atomic and Electronic Structure of Graphene and Graphene Intercalation Compounds. X-Ray Standing Wave and Scanning Tunnelling Microscopy Studies
No full textThe morphology of graphene/Iridium(111) was studied by x-ray standing wave (XSW) measurements. A dependence of the moire corrugation on the graphene coverage is observed. A comparison with density functional theory (DFT) reveals a discrepancy on the corrugation caused by stress appearing from the cool down from the preparation temperature. The model of rehybridised graphene due to cluster adsorption is supported by a structure analysis. Graphene intercalation compounds were investigated by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), and XSW. It is shown that intercalation takes place via cracks and holes at wrinkles and wrinkle crossings. The superstructures of caesium intercalated graphene are resolved. For intercalants interacting mainly via van der Waals forces it could be shown that the graphene-intercalant
distance is dependent on the charge transfer. Moreover, the structure analysis supports that oxygen intercalation leads to quasi freestanding graphene. A rigid-band model is introduced and applied to graphene intercalation compounds. Scanning tunnelling microscopy measurements reveal clear indications for Dirac electron scattering at defects. In these processes the pseudo-spin is not conserved leading to both inter- and intravalley scattering
Single stage electrochemical exfoliation method for the production of few-layer graphene via intercalation of tetraalkylammonium cations
Full text linkWe present a non-oxidative production route to few layer graphene via the electrochemical intercalation of tetraalkylammonium cations into pristine graphite. Two forms of graphite have been studied as the source material with each yielding a slightly different result. Highly orientated pyrolytic graphite (HOPG) offers greater advantages in terms of the exfoliate size but the source electrode set up introduces difficulties to the procedure and requires the use of sonication. Using a graphite rod electrode, few layer graphene flakes (2 nm thickness) are formed directly although the flake diameters from this source are typically small (ca. 100–200 nm). Significantly, for a solvent based route, the graphite rod does not require ultrasonication or any secondary physical processing of the resulting dispersion. Flakes have been characterized using Raman spectroscopy, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS)
Intercalation-Driven Formation of siRNA Nanogels for Cancer Therapy
No full textRNA
interference (RNAi) is a powerful approach in the treatment
of various diseases including cancers. The clinical translation of
small interfering RNA (siRNA)-based therapy requires safe and efficient
delivery vehicles. Here, we report a siRNA nanogels (NG)-based delivery
vehicle, which is driven directly by the intercalation between nucleic
acid bis-intercalator and siRNA molecules. The intercalation-based
siRNA NG exhibits good physiological stability and can enter cells
efficiently via different endocytosis pathways. Furthermore, the siRNA
NG can not only silence the target genes in vitro but also significantly inhibit the tumor growth in vivo. Therefore, this study provides an intercalation-based strategy
for the development of a siRNA delivery platform for cancer therapy.
To the best of our knowledge, this is the first report of the intercalation-driven
siRNA NG
Enhancing Metallicity and Basal Plane Reactivity of 2D Materials via Self-Intercalation
No full textIntercalation (ic) of metal atoms into the van der Waals
(vdW)
gap of layered materials constitutes a facile strategy to create materials
whose properties can be tuned via the concentration of the intercalated
atoms. Here we perform systematic density functional theory calculations
to explore various properties of an emergent class of crystalline
2D materials (ic-2D materials) comprising vdW homobilayers with native
metal atoms on a sublattice of intercalation sites. From an initial
set of 1348 ic-2D materials, generated from 77 vdW homobilayers, we
find 95 structures with good thermodynamic stability (formation energy
within 200 meV/atom of the convex hull). A significant fraction of
the semiconducting host materials are found to undergo an insulator
to metal transition upon self-intercalation, with only PdS2, PdSe2, and GeS2 maintaining a finite electronic
gap. In five cases, self-intercalation introduces magnetism. In general,
self-intercalation is found to promote metallicity and enhance the
chemical reactivity on the basal plane. Based on the calculated H
binding energy, we find that self-intercalated SnS2 and
Hf3Te2 are promising candidates for hydrogen
evolution catalysis. All the stable ic-2D structures and their calculated
properties can be explored in the open C2DB database
Intercalation- and Vacancy-Enhanced Internal Electric Fields in ZnIn2S4 for Highly Efficient Photocatalytic H2O2 Production
No full textDefect engineering and intercalation modification are
feasible
strategies to enhance the internal electric field (IEF), which is
an effective way for steering photogenerated charge kinetics. Herein,
ethylene glycol (EG) and Zn vacancy (VZn) are successfully
introduced into the intra- and interlayers of ZnIn2S4, respectively, based on the two-dimensional layered structure
characteristic of ZnIn2S4 and the special coordination
effect between ethylene glycol and Zn2+. Comprehensive
experimental analysis and theoretical calculations demonstrate that
the synergistic effect of EG intercalation and VZn not
only increases the dipole moment inside the unit cell resulting in
the enhancement of IEF but also facilitates the kinetics of the 2e– oxygen reduction reaction. Consequently, ZnIn2S4 modified by EG intercalation and VZn achieves the desired photocatalytic H2O2 production
capability (1145.6 μmol/g/h), which is about 4 times that of
pristine ZnIn2S4 (294.4 μmol/g/h). This
work provides a reference for enhancing the IEF of ZnIn2S4 through intercalation strategies and defect engineering
to improve its photocatalytic performance
Polymer-clay Nanocomposites
No full textPhDPolymer-clay nanocomposites are attracting global interest principally because
property enhancements are obtained at low clay particle loadings (1-5 wt%).
However there is lack of fundamental understanding of such composites. The aim
of this work is to provide an insight into the interaction between polymer and clay.
This includes the driving force for intercalation, the reinforcement mechanisms and
property-volume fraction relationships.
Functionalised poly(ethylene glycol)-clay, poly(c-caprolactone)-clay and
thermoplastic starch-clay nanocomposites with a range of polymer molecular
weights, clay volume fractions and with different clays were prepared using
solution methods, melt-processing methods, and in situ polymerisation. A reliable
X-ray diffraction technique for low angle basal plane spacing of clay, the essential
parameter for structure determination, was established obtaining ±0.005 Mn
between three diffractometers. The basal plane spacing was found to be unaffected
by polymer molecular weight and preparation method but was affected by the
nature of the polymer and clay. Increasing clay loading could lead to a lower
spacing. As a cautionary observation, poly(ethylene glycol) with high molecular
weight (2: 10,000) was found to undergo degradation readily during preparation of
nanocomposites with and without clay.
Competitive sorption experiments for molecular weight showed that high
molecular weight fractions of polymer intercalate preferentially into clay during
solution preparation. Thermodynamic studies on the intercalation process found
that significant enthalpic change occurred during intercalation, which is coincident
with the observation that heat-treated clays without interlayer water can intercalate
polymer. The calculation of true volume fraction against nominal volume fraction
provided reasonable explanation of property enhancement and helps understand the
relation between nanocomposites and conventional composites. At a given clay
loading, nanocomposites with better dispersion gave more property enhancement
than those with lower dispersion or conventional composites. The crystallinity of
semicrystalline polymer was also affected by varying extents of dispersion of clay.
The use of X-ray diffraction with an internal standard was explored for quantitative
analysis of intercalation and exfoliation
Intercalation-Driven Reversible Switching of 2D Magnetism
No full textThe recent discovery of magnetism in atomically thin
chromium triiodide
has initiated the quest for two-dimensional magnetic materials. In
an alternate route, here we explore the reversible switching of magnetism
in naturally antiferromagnetic monolayer ferrous dioxide. Our high-throughput
spin-polarized density functional theory calculations reveal antiferromagnetic
to ferrimagnetic switching through the manipulation of the local magnetic
moments mediated by lithium and magnesium ion intercalation. Hardware-accelerator-assisted
rigorous ab initio computations involving structure searching, molecular
dynamics, adaptive kinetic Monte Carlo, and hybrid functionals ensure
sustainability of such switching amid randomness, structural deformation,
thermal vibrations, and environmental conditions. The proposed technique
along with conventional lithography may be used to create selective
magnetic zones in a macroscopically nonmagnetic material for spintronics
and memory devices
Intercalation-Induced Ordered Nanostructure in the Interlayer Modified with Methylviologen by Molecular Dynamics Simulation
No full textIntercalation
of phenol in montmorillonite, a representative layered
material, has historically been investigated, and modification of
the interlayer with methylviologen (Mont-MV) results in color change
due to formation of a charge-transfer complex. Its detailed nanostructure,
however, has yet been revealed owing to its small gallery height and
poor crystallinity. In the present study, we performed molecular dynamics
simulation to investigate structural changes in Mont-MV by the intercalation
of phenol. The value of the basal spacing of Mont-MV was well consistent
with that reported experimentally, and the MV cations were distributed
horizontally. Successive intercalation of phenol revealed that the
interlayer swelled nonlinearly and both the MV cations and phenol
molecules were tilted, which were roughly parallel to each other.
The obtained ordered nanostructure was similar to that reported in
the charge-transfer complex crystal of the MV cation and the naphthol
derivative. Thus, the parallel orientation in the interlayer was found
to be the key for the color reaction. Combined with the fact that
the phenol molecules interacted with the Mont layers, the role of
the MV cation was found to be that of a pillar for providing sufficient
gallery height, and the formation of the charge-transfer complex is
the secondarily derived function
Intercalation-Driven Reversible Switching of 2D Magnetism
No full textThe recent discovery of magnetism in atomically thin
chromium triiodide
has initiated the quest for two-dimensional magnetic materials. In
an alternate route, here we explore the reversible switching of magnetism
in naturally antiferromagnetic monolayer ferrous dioxide. Our high-throughput
spin-polarized density functional theory calculations reveal antiferromagnetic
to ferrimagnetic switching through the manipulation of the local magnetic
moments mediated by lithium and magnesium ion intercalation. Hardware-accelerator-assisted
rigorous ab initio computations involving structure searching, molecular
dynamics, adaptive kinetic Monte Carlo, and hybrid functionals ensure
sustainability of such switching amid randomness, structural deformation,
thermal vibrations, and environmental conditions. The proposed technique
along with conventional lithography may be used to create selective
magnetic zones in a macroscopically nonmagnetic material for spintronics
and memory devices
Intercalation-Driven Reversible Switching of 2D Magnetism
No full textThe recent discovery of magnetism in atomically thin
chromium triiodide
has initiated the quest for two-dimensional magnetic materials. In
an alternate route, here we explore the reversible switching of magnetism
in naturally antiferromagnetic monolayer ferrous dioxide. Our high-throughput
spin-polarized density functional theory calculations reveal antiferromagnetic
to ferrimagnetic switching through the manipulation of the local magnetic
moments mediated by lithium and magnesium ion intercalation. Hardware-accelerator-assisted
rigorous ab initio computations involving structure searching, molecular
dynamics, adaptive kinetic Monte Carlo, and hybrid functionals ensure
sustainability of such switching amid randomness, structural deformation,
thermal vibrations, and environmental conditions. The proposed technique
along with conventional lithography may be used to create selective
magnetic zones in a macroscopically nonmagnetic material for spintronics
and memory devices
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