Nuclear Nanotechnology: Mechanisms behind The Formation of Uranium Oxide Nanoparticles

Nanoparticles are interesting due to the unusual properties that they display based on quantum effects, which make their electronic structures intermediate between individual atoms and larger bulk materials. While nanochemistry has been well developed throughout the transition metals, little is known regarding how actinide materials behave when their sizes are reduced to the nanoscale. This is problematic due to the inherent relevance of nanoscale actinides to the nuclear fuel cycle. High burnup structure nuclear fuel results in nanometer-scale grain sizes, and it is well documented that nanoparticle formation greatly affects actinide oxide corrosion and the ability of actinides to move through environmental systems. In order to elucidate size/property relationships in uranium oxides, we have developed procedures to control the size and morphology of uranium oxide nanoparticles through organic phase colloidal synthesis and seed-mediated anisotropic growth. Notably, we have learned the important role that water plays in UO₂ nanoparticle synthesis, which has important implications for nanoparticle synthesis throughout the periodic table. Methods will also be described towards scaling down organic phase colloidal synthesis to achieve actinide oxide nanoparticles that utilize less than 1 mg of precursor, making trans-uranium nanoparticles more feasible to study. Additionally, we demonstrate the formation of unusual uranium oxide nanoparticle 2D superlattices, and how this can be controlled by altering nanoparticle size and morphology.