The route to fullerenoid oxides

Tetrahedral oxides, like silicates and aluminates, have attracted great interest due to their potential for numerous applications in various fields ranging from catalysis, ion exchange and molecular sieves, to thermo- and photoluminescence. In spite of their tetrahedral character, no effort has been made to date for establishing structural relationships between these tetrahedral oxides with different forms of carbon, for example, fullerenes. Here, we report for the first time an oxide that exhibits a three-dimensional framework of AlO4 tetrahedra forming huge 'Al-84' spheres, similar to those of the D2d isomer of the C-84 fullerenes. These Al-84 spheres, displayed in a face-centred-cubic lattice, are easily identified by high-resolution electron microscopy. We also show that this Sr33Bi24+deltaAl48O141+3delta/2 aluminate exhibits an onion-skin-like subnanostructure of its Bi/Sr/O species located inside the Al-84 spheres. The role of the original pseudo-spheric anion [Bi(16)O(52-n)square(n)] - with n vacancies (square) - in the stabilization of such a structure is discussed. This structure seems to be promising for the generation of a large family of fullerene-type (fullerenoid) oxides with various properties.