Surface charge driven growth of eight-branched Cu₂O Crystals

Cu₂O crystals are synthesised hydrothermally with an 8-branched morphology, which can undergo a transition to a cubic shape by increasing the reaction time. The rapid branch formation of these structures is studied over time using SEM, TEM, SAED, PXRD and TGA. The formation of Cu²⁺/PVP soft matter clusters is shown to play a key role in the reduction of Cu²⁺, the nucleation of Cu₂O crystals and the rapid growth of branches along all eight equivalent <111> directions of the cubic Cu₂O struc- ture, due to the presence of negatively charged hydroxyl sites on the {111} surfaces. This non-classical crystal growth mechanism, which relies on aggregation of the precursor on the crystal surface, may help us to understand the formation of many abnormal crystal morphologies.