From Winter Snowflakes to Spring Blossoms: Manipulating the Growth of Copper Sulfide Dendrites

A simple and facile method for the preparation of copper sulfide dendritic structures in high yield under mild conditions is described. This new approach encompasses many advantages over the conventional solvothermal preparations of dendrites in terms of product quality (better morphology control, good monodispersity, and high yield), reaction conditions (lower temperatures and pressures), and shorter reaction time. In addition, temporal growth of the dendrites can be readily followed and manipulated in this preparation via time-resolved microscopic analysis. The crystalline nature of the dendrites was confirmed using high-resolution transmission electron microscopy and selected area electron diffraction. Several factors, including the reaction temperature, time, relative concentration between the reactants, and amine chain length, were identified to be important and investigated in detail. It was demonstrated that the dendritic structures are favored at high ethylenediamine (EDA) and low tributylphosphite (TBPT) concentrations in general. Unprecedented multilayer crystal growth originating from the dendritic core was observed through varying the ratios of the reagents. On the basis of these carefully controlled experiments, a plausible formation mechanism of the dendrites was suggested and discussed. To the best of our knowledge, this is the first report on making crystalline semiconductor dendrites with such full control and tunability of morphology and size.