31 research outputs found
Bridging the Gap: 3D Real-Space Characterization of Colloidal Assemblies via FIB-SEM Tomography
Insight in the structure of nanoparticle assemblies up to a single particle
level is key to understand the collective properties of these assemblies, which
critically depend on the individual particle positions and orientations.
However, the characterization of large, micron sized assemblies containing
small, 10-500 nanometer, sized colloids is highly challenging and cannot easily
be done with the conventional light, electron or X-ray microscopy techniques.
Here, we demonstrate that focused ion beam-scanning electron microscopy
(FIB-SEM) tomography in combination with image processing enables quantitative
real-space studies of ordered and disordered particle assemblies too large for
conventional transmission electron tomography, containing particles too small
for confocal microscopy. First, we demonstrate the high resolution structural
analysis of spherical nanoparticle assemblies, containing small anisotropic
gold nanoparticles. Herein, FIB-SEM tomography allows the characterization of
assembly dimensions which are inaccessible to conventional transmission
electron microscopy. Next, we show that FIB-SEM tomography is capable of
characterizing much larger ordered and disordered assemblies containing silica
colloids with a diameter close to the resolution limit of confocal microscopes.
We determined both the position and the orientation of each individual
(nano)particle in the assemblies by using recently developed particle tracking
routines. Such high precision structural information is essential in the
understanding and design of the collective properties of new nanoparticle based
materials and processes.Comment: 17 pages, 4 figures, Supplemental Information at articles webpage:
https://doi.org/10.1039/C8NR09753
Identification of deformation mechanisms in ice core samples
To determine active deformation mechanisms in polar ice. We use LM and Electron BackScattered Diffraction to identify possible slip systems of subgrain boundaries in EDML (Antarctica) and NEEM (Greenland) ice cores
Frictional properties of megathrust fault gouges at low sliding velocities: New data on effects of normal stress and temperature
Directed Self-Assembly of Micron-Sized Gold Nanoplatelets into Oriented Flexible Stacks with Tunable Interplate Distance
A growing demand for control over
the interparticle spacing and the orientation of anisotropic metallic
particles into self-assembled structures is fuelled by their use in
potential applications such as in plasmonics, catalysis, sensing,
and optoelectronics. Here, we present an improved high yield synthesis
method to fabricate micron- and submicron-sized gold nanoplatelets
with a thickness less than 20 nm using silver nanoplatelets as seeds.
By tuning the depth of the secondary minimum in the DLVO interaction
potential between these particles, we are able to assemble the platelets
into dynamic and flexible stacks containing thousands of platelets
arranged face-to-face with well-defined spacing. Moreover, we demonstrate
that the length of the stacks, and the interplate distance can be
controlled between tens and hundreds of nm with the ionic strength.
We use a high frequency external electric field to control the orientation
of the stacks and direct the stacks into highly organized 2D and 3D
assemblies that strongly polarize light
Topographic features of nano-pores within the osteochondral interface and their effects on transport properties -a 3D imaging and modeling study
Recent insights suggest that the osteochondral interface plays a central role in maintaining healthy articulating joints. Uncovering the underlying transport mechanisms is key to the understanding of the cross-talk between articular cartilage and subchondral bone. Here, we describe the mechanisms that facilitate transport at the osteochondral interface. Using scanning electron microscopy (SEM), we found a continuous transition of mineralization architecture from the non-calcified cartilage towards the calcified cartilage. This refurbishes the classical picture of the so-called tidemark; a well-defined discontinuity at the osteochondral interface. Using focused-ion-beam SEM (FIB-SEM) on one osteochondral plug derived from a human cadaveric knee, we elucidated that the pore structure gradually varies from the calcified cartilage towards the subchondral bone plate. We identified nano-pores with radius of 10.71 ± 6.45 nm in calcified cartilage to 39.1 ± 26.17 nm in the subchondral bone plate. The extracted pore sizes were used to construct 3D pore-scale numerical models to explore the effect of pore sizes and connectivity among different pores. Results indicated that connectivity of nano-pores in calcified cartilage is highly compromised compared to the subchondral bone plate. Flow simulations showed a permeability decrease by about 2000-fold and solute transport simulations using a tracer (iodixanol, 1.5 kDa with a free diffusivity of 2.5 × 10-10 m2/s) showed diffusivity decrease by a factor of 1.5. Taken together, architecture of the nano-pores and the complex mineralization pattern in the osteochondral interface considerably impacts the cross-talk between cartilage and bone
Nanoscale Chemical Imaging of Coking Mechanisms in a Zeolite ZSM-5 Crystal by Atom Probe Tomography
Topographic features of nano-pores within the osteochondral interface and their effects on transport properties -a 3D imaging and modeling study
Recent insights suggest that the osteochondral interface plays a central role in maintaining healthy articulating joints. Uncovering the underlying transport mechanisms is key to the understanding of the cross-talk between articular cartilage and subchondral bone. Here, we describe the mechanisms that facilitate transport at the osteochondral interface. Using scanning electron microscopy (SEM), we found a continuous transition of mineralization architecture from the non-calcified cartilage towards the calcified cartilage. This refurbishes the classical picture of the so-called tidemark; a well-defined discontinuity at the osteochondral interface. Using focused-ion-beam SEM (FIB-SEM) on one osteochondral plug derived from a human cadaveric knee, we elucidated that the pore structure gradually varies from the calcified cartilage towards the subchondral bone plate. We identified nano-pores with radius of 10.71 ± 6.45 nm in calcified cartilage to 39.1 ± 26.17 nm in the subchondral bone plate. The extracted pore sizes were used to construct 3D pore-scale numerical models to explore the effect of pore sizes and connectivity among different pores. Results indicated that connectivity of nano-pores in calcified cartilage is highly compromised compared to the subchondral bone plate. Flow simulations showed a permeability decrease by about 2000-fold and solute transport simulations using a tracer (iodixanol, 1.5 kDa with a free diffusivity of 2.5 × 10-10 m2/s) showed diffusivity decrease by a factor of 1.5. Taken together, architecture of the nano-pores and the complex mineralization pattern in the osteochondral interface considerably impacts the cross-talk between cartilage and bone
Electron crystallography with the EIGER detector
<p>Electron diffraction data as part of the publiation https://doi.org/10.1107/S2052252518000945https://doi.org/10.1107/S2052252518000945; Data set with 60keV Threshold. For experimental details see XDS.INP file.</p