PbS sub-micrometer structures with anisotropic shape: Ribbons, wires, octapods, and hollowed cubes

The current paper discusses the preparation, characterization, and clarification of the growth mechanism of PbS wires, ribbons, octapods, and hollowed cubes. Those sub-micrometer structures were prepared by a thermal decomposition of a uni-precursor {[Pb(S₂CNEt₂) ₂]₂}, using either ethylene diamine (en) or ethylene glycol (eg) as an intermediate reagent, as well as surfactants. The growth in eg produced mainly ribbons and square plates, while the growth in en solutions produced wires at the lower temperatures (80°C) and octapods and hollowed cubes at elevated temperatures (117°C). The experimental observations suggest that the obtained morphologies are primarily determined by the nucleation phase and the subsequent growth kinetics. The growth process developed according to the characteristic habit and subsequent branching processes. The characteristic habit was controlled by the surface energy of the facets and their modulation by the solvent molecules. The branching process was determined by a delicate balance between kinetic and thermodynamic processes, and it was controlled by the variation of the temperature and duration of the reactions.