16 research outputs found
Solvothermal synthesis and characterization of ytterbium/iron mixed oxide nanoparticles with potential functionalities for applications as multiplatform contrast agent in medical image techniques
A solvothermal route to prepare Glutathione capped hybrid ytterbium/iron oxide nanoparticles with potential applications as multiplatform contrast agent in medical image techniques has been developed. The influence of ytterbium/iron molar ratio used as precursor, as well as the degree of the autoclave filling on the structural and morphological characteristics of the obtained nanoparticles has been extensively studied. Although all nanoparticles present similar composition, with YbFeO3 being the majority phase, size and morphology of the as synthetized nanoparticles are highly influenced by the critical temperature and by the over -saturation reached during the solvothermal process. We have demonstrated that glutathione properly functionalizes the hybrid nanoparticles, increasing their colloidal stability and decreasing their cytotoxicity. Additionally, they show good imaging in magnetic resonance and X-ray computerized tomography, thereby indicating promising potential as a dual contrast agent. This work presents, for the first time, glutathione functionalized ytterbium/iron oxide nanoparticles with potential applications in Biomedicine. © 2022 Elsevier Ltd and Techna Group S.r.l
Quantitative, Spectro-kinetic Analysis of Oxygen in Electron-Beam Sensitive, Multimetallic Oxide Nanostructures
The oxygen stoichiometry of hollandite, KxMnO2-δ, nanorods has been accurately determined from a quantitative analysis of scanning-transmission electron microscopy (STEM) X-Ray Energy Dispersive Spectroscopy (XEDS) experiments carried out in chrono-spectroscopy mode. A methodology combining 3D reconstructions of high-angle annular dark field electron tomography experiments, using compressed-sensing algorithms, and quantification through the so-called ζ-factors method of XEDS spectra recorded on a high-sensitivity detector has been devised to determine the time evolution of the oxygen content of nanostructures of electron-beam sensitive oxides. Kinetic modeling of O-stoichiometry data provided K0.13MnO1.98 as overall composition for nanorods of the hollandite. The quantitative agreement, within a 1% mol error, observed with results obtained by macroscopic techniques (temperature-programmed reduction and neutron diffraction) validate the proposed methodology for the quantitative analysis, at the nanoscale, of light elements, as it is the case of oxygen, in the presence of heavy ones (K, Mn) in the highly compromised case of nanostructured materials which are prone to electron-beam reduction. Moreover, quantitative comparison of oxygen evolution data measured at macroscopic and nanoscopic levels allowed us to rationalize beam damage effects in structural terms and clarify the exact nature of the different steps involved in the reduction of these oxides with hydrogen.Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEpu
Improving the Redox Response Stability of Ceria-Zirconia Nanocatalysts under Harsh Temperature Conditions
By
depositing ceria on the surface of yttrium-stabilized zirconia
(YSZ) nanocrystals and further activation under high-temperature reducing
conditions, a 13% mol. CeO<sub>2</sub>/YSZ catalyst structured as
subnanometer thick, pyrochlore-type, ceria-zirconia islands has been
prepared. This nanostructured catalyst depicts not only high oxygen
storage capacity (OSC) values but, more importantly, an outstandingly
stable redox response upon oxidation and reduction treatments at very
high temperatures, above 1000 °C. This behavior largely improves
that observed on conventional ceria-zirconia solid solutions, not
only of the same composition but also of those with much higher molar
cerium contents. Advanced scanning transmission electron microscopy
(STEM-XEDS) studies have revealed as key not only to detect the actual
state of the lanthanide in this novel nanocatalyst but also to rationalize
its unusual resistance to redox deactivation at very high temperatures.
In particular, high-resolution X-ray dispersive energy studies have
revealed the presence of unique bilayer ceria islands on top of the
surface of YSZ nanocrystals, which remain at surface positions upon
oxidation and reduction treatments up to 1000 °C. Diffusion of
ceria into the bulk of these crystallites upon oxidation at 1100 °C
irreversibly deteriorates both the reducibility and OSC of this nanostructured
catalyst