Multifunctional Rare Earth Vanadate Nanoparticles: Luminescent Labels, Oxidant Sensors and Magnetic Resonance Imaging Contrast Agents

Abstract : Multimodal imaging techniques are of great interest due to the wealth of information they provide. This thesis is devoted to the development and characterization of nanoparticles which can be applied as luminescent probes, for oxidant detection and as contrast agents in magnetic resonance imaging. The work is based on previous studies on Y0.6Eu0.4VO4 nanoparticles which show strong, non-blinking and stable luminescence. Time and space resolved optical oxidant detection is feasible after reversible photoreduction of Eu3+ to Eu2+ by e. g. H2O2. This oxidation is detectable by a modification of the luminescence properties. The incorporation of paramagnetic Gd3+ confers proton relaxation enhancing properties to the system. We synthesized nanoparticles of either 10 nm or 40 nm diameter and of the compositions GdVO4 and Gd0.6Eu0.4VO4 as well as core-shell systems containing a Y0.6Eu0.4VO4 core and a GdVO4 shell with 40 nm total diameter. X-ray microstructural analysis in combination with dynamic light scattering and electron microscopy enabled us to propose a model for the relationship between the shape of the nanoparticles and the crystallites contained in them. Complexometric titration indicated that rare earth leaching is negligible making this type of nanoparticles well suited for in vivo applications. We demonstrated that even after substitution of Y3+ by Gd3+, the nanoparticles retain the ability of H2O2 detection by luminescence modulation. Temperature and magnetic field dependent measurements of the magnetization of Gd0.6Eu0.4VO4 nanoparticles confirmed the paramagnetic behavior according to a Curie-Weiss law in the temperature range from 290 K down to 5 K. We found that the proton relaxivity of GdVO4 and Gd0.6Eu0.4VO4 nanoparticles of 10 nm diameter as well as of the core-shell nanoparticles is higher than that of the commercial chelate compound Dotarem®. Nuclear magnetic resonance dispersion spectroscopy showed higher proton relaxivities for nanoparticles made up from Gd0.6Eu0.4VO4 than from pure GdVO4. The present data suggest that rare earth vanadate nanoparticles containing simultaneously Gd and Eu are very promising candidates for applications as in vivo multifunctional probe. This system might also be useful as a target in gadolinium neutron capture therapy or for positron emission tomography.
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https://pastel.archives-ouvertes.fr/pastel-00688113
Contributor : Markus Schoeffel <>
Submitted on : Monday, April 16, 2012 - 4:28:31 PM
Last modification on : Wednesday, January 23, 2019 - 10:29:00 AM
Long-term archiving on : Tuesday, July 17, 2012 - 2:30:31 AM

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Markus Schoeffel. Multifunctional Rare Earth Vanadate Nanoparticles: Luminescent Labels, Oxidant Sensors and Magnetic Resonance Imaging Contrast Agents. Materials Science [cond-mat.mtrl-sci]. Ecole Polytechnique X, 2012. English. ⟨pastel-00688113⟩

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