Polyol-mediated synthesis of PbS crystals: Shape evolution and growth mechanism

An interesting shape evolution of. PbS crystals, that is, from cubes to (truncated) octahedra and finally to stable star-shaped multipods with six arms along the < 100 > directions is first realized via a facile polyol-mediated reaction between lead acetate and sulfur powder in the absence of surfactants. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) techniques were employed to characterize the samples. We elucidate the important parameters (including reaction temperature and sulfur sources) responsible for the shape-controlled synthesis of PbS crystals. The possible formation mechanism for products with various architectures are presented, which is mainly based on the, variation of the ratio (R) of the growth rates along the < 100 > direction and < 111 > direction. In addition, the effect of the diffusion-controlled branching growth on the formation of the multiarmed structure is also taken into account. This polyol-mediated method-should be readily extended to the controlled synthesis of other metal chalcogenides and the proposed growth model could also be used to explain and direct the growth of crystals with a face-centered cubic (fee) structure.