Naturally occurring nanoparticles are ubiquitous and important in many processes such as weathering and biological processes. Natural water-born nanoparticles can govern the mobility of trace metals in the environment due to their small size and high chemical reactivity. Nanoscale uranyl peroxide cage clusters, which are similar in topology to some transition metal polyoxometalates, are self-assembled structures with uranyl polyhedra linked through peroxide bridges. While peroxide bridges between uranyl polyhedra are necessary to foster curvature, introduction of other functional groups such as oxalate, pyrophosphate and hydroxyl leads to chemically varied nanocluster structures. Charge-balancing alkali ions are located both inside and outside of these negatively charged nanoscale capsules. Due to their unique properties, uranyl peroxide clusters have potential applications in the nuclear fuel cycle. Yet, their thermodynamic properties are poorly studied. In this study, the enthalpy of formation of crystals containing six different uranyl peroxide clusters with different ligands and different numbers of uranyl polyhedra, as well as charge balancing alkali ions, were determined using a high-temperature calorimeter. The roles of the type and the number of alkali ions as well as the type of ligands in the stability of these structures were studied separately to determine the factors affecting the structural stability of uranyl nanoclusters.

Structural stability of uranyl nanoclusters

253rd National Meeting (2017)

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