A comprehensive study of the crystallization mechanism involved in the nonaqueous formation of tungstite

Abstract

We present a detailed study on the nonaqueous synthesis of tungstite nanostructures with the focus on crystallization processes and the evolution of particle morphology. Time-dependent transmission electron microscopy (TEM) revealed a complex, particle-based crystallization mechanism involving first the formation of spherical and single-crystalline primary particles of 2-8 nm, which are cross-linked to large and unordered agglomerates, followed by their organization into rod-like structures of 40 × 200-400 nm. These rods undergo an internal ordering process, during which crystallographically oriented stacks of platelets develop. In situ small angle X-ray scattering (SAXS) experiments confirm this pathway of particle formation. The scattering intensity is dominated by the fast formation of rod-like particles, which cause an inter-platelet peak in the SAXS pattern with ongoing internal ordering. With continuous reaction time, the platelet stacks start to fall apart forming shorter assemblies of just a few platelets or even single platelets.