Arresting butterfly-like intermediate nanocrystals of beta-Co(OH)2 via ethylenediamine-mediated synthesis.

A synthesis of beta-Co(OH)2 nanocrystalline materials has been investigated with the assistance of chelating agent ethylenediamine. By controlling precipitation processes, various forms of beta-Co(OH)2 crystallites can be prepared at different stages. The crystallite morphologies include two-dimensional hexagonal sheet platelets, one-dimensional nanorods, and butterfly-like nanocrystallite intermediates. In particular, a triangular construction unit for beta-Co(OH)2 crystallites has been revealed with the ethylenediamine mediation in the synthesis. With the successful arrest of these butterfly-like intermediate crystallites, especially of linearly aligned "butterflies", the formation mechanism of one-dimensional nanorods or nanoribbons has been experimentally explained. The chemical composition of solution precursors and resultant beta-Co(OH)2 crystallites has been analyzed with UV-vis/FTIR/CHN /XRD/TGA/TEM/SAED methods. The relationships among various observed crystallite morphologies have also been discussed on the basis of the experimental findings.