Nanobubbles within a microbubble: synthesis and self-assembly of hollow manganese silicate and its metal-doped derivatives.

We developed a surface-catalyzed dual templating strategy to synthesize and organize hollow spheres of manganese silicate as well as a wide variety of its metal-doped structural derivatives (where metal dopant = Fe, Co, Ni, Cu, Y, La, Ce, Nd, Eu, Gd, Er, and Yb). The size of hollow spheres obtained is in the range of only 7-9 nm. In addition, the resultant nanospheres can also be formed into an even greater hollow sphere, giving rise to a "bubbles within a bubble" assemblage in the submicrometer regime (e.g., ∼200 to 270 nm). The hierarchical hollow structures of this type were further tested for catalytic degradation (or decomposition) of organic dyes and used as solid precursors for transformative synthesis of other silicon-based functional hollow materials.