3D environmental studies of the microstructure engineering of vanadate based phosphors at the nanoscale – 3D-NANOREV

Emerging applications of oxide nanoparticles inspire an in-depth comprehension on balancing their structure, surface and composition to afford multiple functionalities. Rare earth vanadates are archetypical luminescent materials that enable not only fundamental detailing on solid-state mechanisms and defect engineering, but also envisaging combined thermometry, chemical sensing, and nanozyme catalysis. However, steps governing the production of colloidal nanoparticles with optimised microstructure and controlled stoichiometry are often unclear. We previously demonstrated the generation of porous vanadate nanoparticles by aggregation of ~2 nm primary grains or by Kirkendall effect-driven crystallisation at a template surface. Rationalisation of the uncontrolled formation of nanovoids upon heating (sinkhole), the role of occluded amorphous phases on final defect densities and on the formation of hetero-nanostructures and the mechanisms involved in diffusion-limited interface crystallisation are still open questions. Correlating such observations to spectroscopic properties, energy transfer mechanisms and redox activity will provide key answers to develop new multimodal nanomaterials. We therefore aim to combine controlled synthesis with advanced in situ transmission electron microscopy to afford new insights on the chemistry of luminescent nanoparticles from solution to the solid-state. We intend to study nanoscale phase and morphological transitions under controlled environmental conditions of temperature and atmosphere according to two experimental axes, (i) the realisation of observations in a dedicated environmental microscope in which the object chamber will constitute a perfectly controlled nano-reactor, (ii) the realisation of the acquisition by 3D electron tomography of the samples that have undergone the different environmental conditions. The concepts and methods developed herein will then be transposed to different families of oxide luminescent materials.