Formation of Silicalite-1 Hollow Spheres by the Self-assembly of Nanocrystals

A simple approach is reported for the preparation of hollow spheres with a 10−20-nm-thick shell of silicalite-1 nanocrystals. The nanocrystals were produced by the steaming of silicalite-1 nanoprecursors (NPs), collected with the help of surfactant from a clear synthesis solution immediately following the induction period. The nanocrystals produced were ≈10−20 nm with a BET surface area of 440−470 m2/g and an external surface area >112 m2/g. A water adsorption isotherm confirmed that the nanocrystals were hydrophobic in nature. These nanocrystals self-assembled into hollow spheres of 100−300-nm diameter when ultrasonicated in ammoniac ethanol.