3 research outputs found
Combined Computed Nanotomography and Nanoscopic X‑ray Fluorescence Imaging of Cobalt Nanoparticles in Caenorhabditis elegans
Synchrotron
radiation phase-contrast computed nanotomography (nano-CT)
and two- and three-dimensional (2D and 3D) nanoscopic X-ray fluorescence (nano-XRF) were used to
investigate the internal distribution of engineered cobalt nanoparticles
(Co NPs) in exposed individuals of the nematode Caenorhabditis
elegans. Whole nematodes and selected tissues and
organs were 3D-rendered: anatomical 3D renderings with 50 nm voxel
size enabled the visualization of spherical nanoparticle aggregates
with size up to 200 nm within intact C. elegans. A 20 × 37 nm<sup>2</sup> high-brilliance beam was employed
to obtain XRF elemental distribution maps of entire nematodes or anatomical
details such as embryos, which could be compared with the CT data.
These maps showed Co NPs to be predominantly present within the intestine
and the epithelium, and they were not colocalized with Zn granules
found in the lysosome-containing vesicles or Fe agglomerates in the
intestine. Iterated XRF scanning of a specimen at 0° and 90°
angles suggested that NP aggregates were translocated into tissues
outside of the intestinal lumen. Virtual slicing by means of 2D XRF
tomography, combined with holotomography, indicated presumable presence
of individual NP aggregates inside the uterus and within embryos
Role of Coating-Metallic Support Interaction in the Properties of Electrosynthesized Rh-Based Structured Catalysts
Rh-structured catalysts for the catalytic
partial oxidation of
CH<sub>4</sub> to syngas were prepared by electrosynthesis of Rh-containing
hydrotalcite-type (HT) compounds on FeCrAlloy foams followed by calcination
at 900 °C. During the calcination the simultaneous decomposition
of the layered HT structure and formation of the protective FeCrAlloy
outer shell in alumina occurred. Here, we studied the role of the
coating-metallic support interaction in the properties of the catalysts
after calcination, H<sub>2</sub> reduction, and catalytic tests, by
a combination of electron (FEG-SEM/EDS) and synchrotron X-ray (XRF/XRPD
and XRF/XANES) microscopic techniques. The characterization of crystalline
phases in the metallic support and coating and distribution of Rh
active species was carried out on several samples prepared by modifying
the Rh content in the electrolytic solution (Rh/Mg/Al = 11.0/70.0/19.0,
5.0/70.0/25.0, 0/70.0/30.0 atomic ratio). A sample was also prepared
with no aluminum in the electrolytic solution (Rh/Mg/Al = 13.6/86.4/0.0
atomic ratio) and calcined at 550 and 900 °C. The interaction
between the elements of the metallic support and the catalytic coating
increased the film adhesion during the thermal treatment and catalytic
tests and modified the catalyst crystalline phases. A chemical reaction
between Al coming from the foam and Mg in the coating occurred during
calcination at high temperature leading to the formation of spinel
phases in which rhodium is solved, together with some Rh<sub>2</sub>O<sub>3</sub> and Rh<sup>0</sup>. The metallic support was oxidized
forming the corundum scale and chromium oxides, moreover ι-Al<sub>2</sub>O<sub>3</sub> was identified. For the Rh<sub>11.0</sub>Mg<sub>70.0</sub>Al<sub>19.0</sub> catalyst the inclusion of Rh in the spinel
phase decreased its reducibility in the H<sub>2</sub> pretreatment.
The reduction continued during catalytic tests by feeding diluted
CH<sub>4</sub>/O<sub>2</sub>/He gas mixtures, evidenced by the catalyst
activation. While under concentrated gas mixtures the deactivation
occurred, probably by oxidation
Synchrotron XRF and Histological Analyses Identify Damage to Digestive Tract of Uranium NP-Exposed Daphnia magna
Micro- and nanoscopic X-ray techniques were used to investigate
the relationship between uranium (U) tissue distributions and adverse
effects to the digestive tract of aquatic model organism Daphnia magna following uranium nanoparticle (UNP)
exposure. X-ray absorption computed tomography measurements of intact
daphnids exposed to sublethal concentrations of UNPs or a U reference
solution (URef) showed adverse morphological changes to
the midgut and the hepatic ceca. Histological analyses of exposed
organisms revealed a high proportion of abnormal and irregularly shaped
intestinal epithelial cells. Disruption of the hepatic ceca and midgut
epithelial tissues implied digestive functions and intestinal barriers
were compromised. Synchrotron-based micro X-ray fluorescence (XRF)
elemental mapping identified U co-localized with morphological changes,
with substantial accumulation of U in the lumen as well as in the
epithelial tissues. Utilizing high-resolution nano-XRF, 400–1000
nm sized U particulates could be identified throughout the midgut
and within hepatic ceca cells, coinciding with tissue damages. The
results highlight disruption of intestinal function as an important
mode of action of acute U toxicity in D. magna and that midgut epithelial cells as well as the hepatic ceca are
key target organs