Self-defined intermediate product captured from the evolution process from six-pod to octahedral PbS sub-micrometer particle
Sub-micrometer PbS particle with hierarchical structure, in which each octahedron was composed of six self-defined sub-octahedrons, was captured as the intermediate product in an evolution process from six-pod to octahedral shape PbS crystal. The six sub-octahedrons of each octahedron presented almost intact octahedral morphology as well. Cl- was found to be a good structure-directing agent that changed the growth habit of the PbS crystals and helped the formation of hierarchical octahedron (HO). Compared with other reported products with the similar octahedral growth habit, the formation of HO desired a special equilibrium between thermodynamic and kinetic growth regime, which resulted in the ratio of average growth rate along <100> direction to that of <111> exactly to be 3.46. Local supersaturation degree (LSD) around each individual nucleus was proposed to represent the real driving force deciding the different growth mechanisms. Our work would be helpful for the design and synthesis of desired structures which are thermodynamically unstable.