On-line plasma FIB for x-ray microscopy mesoscale analysis
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36 MATERIALS SCIENCE↗
Engineering topics
Pattammattel, Ajith
Publications and source records attributed to Pattammattel, Ajith.
Temporal and spatial resolution of magnetosome degradation at the subcellular level in a 3D lung carcinoma model
Magnetic nanoparticles offer many exciting possibilities in biomedicine, from cell imaging to cancer treatment. One of the currently researched nanoparticles are magnetosomes, magnetite nanoparticles of high chemical purity synthesized by magnetotactic bacteria. Despite their therapeutic potential, very little is known about their degradation in human cells, and even less so of their degradation within tumours. In an effort to explore the potential of magnetosomes for cancer treatment, we have explored their degradation process in a 3D human lung carcinoma model at the subcellular level and with nanometre scale resolution. We have used state of the art hard X-ray probes (nano-XANES and nano-XRF), which allow for identification of distinct iron phases in each region of the cell. Our results reveal the progression of magnetite oxidation to maghemite within magnetosomes, and the biosynthesis of magnetite and ferrihydrite by ferritin.
36 MATERIALS SCIENCE↗
Alloying effects on the microstructure and properties of laser additively manufactured tungsten materials
A large body of literature within the additive manufacturing (AM) community has focused on successfully creating stable tungsten (W) microstructures due to significant interest in their application for extreme environments. However, cracking and additional embrittling features at grain boundaries have resulted in poorly performing materials, stymying the application of AM as a manufacturing technique for W. Several alloying strategies, such as ceramic particles and ductile elements, have emerged with the promise to eliminate cracking while simultaneously enhancing stability against recrystallization. Here, in this work, we provide new insights regarding the defects and microstructural features that result from the introduction of ZrC for grain refinement and NiFe as a ductile reinforcement phase – in addition to the resulting thermophysical and mechanical properties. ZrC is shown to promote microstructural stability with increased hardness due to the formation of ZrO 2 dispersoids. Conversely, NiFe forms into micron-scale FCC phase regions within a BCC W matrix, producing enhanced toughness relative to pure AM W. A combination of these effects is realized in the WNiFe + ZrC system and demonstrates that complex chemical environments coupled with the tuning of AM microstructures provides an effective pathway for enabling laser AM W materials with enhanced stability and performance.
36 MATERIALS SCIENCE↗
Benchmarking of X‐Ray Fluorescence Microscopy with Ion Beam Implanted Samples Showing Detection Sensitivity of Hundreds of Atoms
Abstract Single impurities in insulators are now often used for quantum sensors and single photon sources, while nanoscale semiconductor doping features are being constructed for electrical contacts in quantum technology devices, implying that new methods for sensitive, non‐destructive imaging of single‐ or few‐atom structures are needed. X‐ray fluorescence (XRF) can provide nanoscale imaging with chemical specificity, and features comprising as few as 100 000 atoms have been detected without any need for specialized or destructive sample preparation. Presently, the ultimate limits of sensitivity of XRF are unknown – here, gallium dopants in silicon are investigated using a high brilliance, synchrotron source collimated to a small spot. It is demonstrated that with a single‐pixel integration time of 1 s, the sensitivity is sufficient to identify a single isolated feature of only 3000 Ga impurities (a mass of just 350 zg). With increased integration (25 s), 650 impurities can be detected. The results are quantified using a calibration sample consisting of precisely controlled numbers of implanted atoms in nanometer‐sized structures. The results show that such features can now be mapped quantitatively when calibration samples are used, and suggest that, in the near future, planned upgrades to XRF facilities might achieve single‐atom sensitivity.
36 MATERIALS SCIENCE↗
Enhanced magnetic susceptibility in Ti 3 C 2 T x MXene with Co and Ni incorporation
We incorporate dilute concentrations of Ni and Co into Ti 3 C 2 T x MXene, resulting in a >50 fold increase in magnetic susceptibility.
36 MATERIALS SCIENCE↗
Deep learning enhanced super-resolution x-ray fluorescence microscopy by a dual-branch network
X-ray fluorescence (XRF) microscopy is a powerful technique for quantifying the distribution of elements in complex materials, which makes it a crucial imaging technique across a wide range of disciplines in physical and biological sciences, including chemistry, materials science, microbiology, and geosciences. However, as a scanning microscopy technique, the spatial resolution of XRF imaging is inherently constrained by the x-ray probe profile and scanning step size. Here we propose a dual-branch machine learning (ML) model, which can extract scale-variant features and bypass abundant low-frequency information separately, to enhance the spatial resolution of the XRF images by mitigating the effects of blurring from the probe profile. The model is trained by simulated natural images, and a two-stage training strategy is used to overcome the domain gap between the natural images and experimental data. The tomography reconstruction from enhanced XRF projections shows an improvement in resolution by a scale factor of four and reveals distinct internal features invisible in low-resolution XRF within a battery sample. This study offers a promising approach for obtaining high-resolution XRF imaging from its low-resolution version, paving the way for future investigations in a broader range of disciplines and materials.
36 MATERIALS SCIENCE↗
Accelerating nano-XANES imaging via feature selection
We utilize feature selection to reduce experimental time by ∼80% of a nanoscale X-ray Absorption Fine Structure (XANES) spectroscopy imaging study of a sample with Fe-bearing mineral phases.
36 MATERIALS SCIENCE↗
High-resolution imaging of Hg/Se aggregates in the brain of small Indian mongoose, a wild terrestrial species: insights into intracellular Hg detoxification
Human activities result in the emission of 2000 metric tons of mercury compounds annually. Mercury (Hg) biomagnification has been characterized in marine mammals and predatory fish; however, little is known about mercury accumulation in brains of wild terrestrial species. Elevated Hg content, of 1.27 μg/g wet wt.—found in the brain of wild small Indian mongoose, prompted us to use synchrotron X-ray fluorescence imaging for simultaneous, quantitative mapping of biologically relevant and neurotoxic elements with high spatial resolution. X-ray fluorescence combined with immunohistochemistry revealed ~0.5–1.9 micron Hg-rich aggregates in cells of the choroid plexus and astrocytes of the subventricular wall in the mongoose brain. Hg content within aggregates correlated with selenium. Hg aggregates did not co-localize with lysosomes. The low Hg density inside aggregates indicated diffuse Hg binding to a Se-containing biomolecule, rather than much denser HgSe nanoparticles proposed to form in other species. Our data show the susceptibility of the small Indian mongoose population to Hg pollution and highlight the vulnerability of the brain as an organ targeted by mercury. Data also provide evidence on the adaptation in the form of a Se-based detoxification mechanism sequestering Hg into intracellular aggregates.
36 MATERIALS SCIENCE↗
Symmetry-specific characterization of bond orientation order in DNA-assembled nanoparticle lattices
Bond-orientational order in DNA-assembled nanoparticles lattices is explored with the help of recently introduced Symmetry-specific Bond Order Parameters (SymBOPs). Here, this approach provides a more sensitive analysis of local order than traditional scalar BOPs, facilitating the identification of coherent domains at the single bond level. The present study expands the method initially developed for assemblies of anisotropic particles to the isotropic ones or cases where particle orientation information is unavailable. The SymBOP analysis was applied to experiments on DNA-frame-based assembly of nanoparticle lattices. It proved highly sensitive in identifying coherent crystalline domains with different orientations, as well as detecting topological defects, such as dislocations. Furthermore, the analysis distinguishes individual sublattices within a single crystalline domain, such as pair of interpenetrating FCC lattices within a cubic diamond. The results underscore the versatility and robustness of SymBOPs in characterizing ordering phenomena, making them valuable tools for investigating structural properties in various systems.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
A general image misalignment correction method for tomography experiments
Not Available
36 MATERIALS SCIENCE↗
Multielectrode electrochemical cell for in situ structural characterization of amorphous thin-film catalysts using high-energy X-ray scattering
A multielectrode-based electrochemical cell allows the structural characterization of an amorphous thin-film water oxidation catalyst under various electrochemical potentials using high-energy X-ray scattering and atomic pair distribution function (PDF) techniques. A multielectrode with five electrodes provides a sufficiently low background signal to enable high-energy X-ray scattering (HEXS) measurements and amplifies the extremely low HEXS signals from samples for high-resolution PDF analysis of in situ data from thin-film catalysts. Glassy carbon (GC) creates a relatively low intensity HEXS pattern and is used as a working electrode. Instead of a three-dimensional (3D) porous electrode architecture, the flat geometry of the electrode enables various deposition techniques to be used for the preparation of a highly conductive metal oxide layer. PDF analysis demonstrates high spatial resolution for a 230 nm thick amorphous iridium oxide film deposited on two roughened 60 µm thick GC electrodes. The PDF analysis resolves the domain size and distinguishes changes in fine structure which are directly correlated with the structure and function of the catalysts. In conclusion, the results bring the opportunity to analyze the structure of nanometre-scale amorphous thin-film catalysts in an electrolyte-compatible and compact 3D-printed electrochemical cell in a three-electrode configuration.
36 MATERIALS SCIENCE↗