Crystallization via Oriented Attachment of Nanoclusters with Short-Range Order in Solution

Many mineral crystallization processes in aqueous solutions involve formation of nanoclusters with short-range order. Their transformation into crystalline products is not well understood. Here we investigate the formation of long-range crystalline order within networks of cobalt-based nanoclusters. High-resolution cryogenic transmission electron microscopy (cryoTEM) together with NMR and FTIR spectroscopies shows the formation of similar to 0.8 nm sized (Co)(NH3)(5)CO3 complexes at the initial stage. By ligand exchange, those complexes become bridged by CO32-/OH- ligands and form similar to 2 nm sized clusters, which subsequently aggregate into sheetlike networks due to the structural heterogeneity of the clusters. By further ligand change and adjustment in cluster orientations, long-range order is established, which leads to the nucleation of ammonium cobalt kambaldaite nanocrystals. Our observations demonstrate that nanoclusters with short-range order can form crystals via an oriented-attachment pathway, which provides new insights into multistep crystallization processes.

Automated summary

Many mineral crystallization processes involve the formation of nanoclusters with short-range order, which can transform into crystals via an oriented-attachment pathway by ligand exchange and cluster orientation adjustment. This study provides new insights into multistep crystallization processes.