Nanostructured actinide compounds

A brief overview of nanostructured inorganic actinide compounds, i.e., compounds with nanoscale clusters and structural units, is given. Only structures that are accessible via X-ray diffraction analysis are considered (i.e., highly ordered assemblies of molecular units with at least one dimension of more than 1 nm). Zero-dimensional (0D) actinide based nanostructures are represented by a new family of self-assembling actinide nanospheres recently reported by Burns et al. [P.C. Burns, K.-A. Hughes Kubatko, G. Sigmon, B.J. Fryer, J.E. Gagnon, M.R. Antonio, L. Soderholm, Angew. Chem. Int. Ed. 44 (2005) 2135]. The nanospheres are comprised of linear actinyl-peroxide building blocks, and their persistence as stable entities in alkaline solutions has been confirmed. Krivovichev et al. [S.V. Krivovichev, V. Kahlenberg, R. Kaindl, E. Mersdorf, I.G. Tananaev, B.F. Myasoedov, Angew. Chem. Int. Ed. 44 (2005) 1134; J. Am. Chem. Soc. 127 (2005) 1072] have recently reported synthesis and structures of two uranium(VI) compounds, K5[(UO2)3(SeO4)5](NO3)(H2O)3.5 (1) and (C4H12N)14 [(UO2)10(SeO4)17(H2O)] (2), containing nanometer-sized tubules formed by corner sharing of U6+O7 pentagonal bipyramids and SeO4 tetrahedra. Actinide peroxide nanospheres and uranyl selenate nanotubules represent the first examples of nanoscale structures in inorganic actinide compounds. These findings demonstrate the possibility of nanoscale fabrication for actinides in higher oxidation states, and a whole new range of uranium-based nanotubular and nanocomposite materials can be expected.