l-Cysteine-Assisted Self-Assembly of Complex PbS Structures

An l-cysteine-assisted self-assembly process for constructing complex PbS from cubes to star and dendritic structures via hydrothermal routes is reported. In this process, l-cysteine (Cys) was used as both a sulfur source and a chelating reagent. The effects of the molar ratios of Cys/Pb²⁺, the concentrations, reaction time and temperature on the self-assembly of PbS microcrystals were investigated. The X-ray diffraction (XRD) patterns confirmed the crystalline structure of PbS crystals. Raman spectroscopy helped to further demonstrate the purity of the products. Transmission electron microscopy (TEM) helped to determine the size and shape of the products. On the basis of systemic studies about the influence of experimental parameters on the products, possible evolution processes were proposed. The shape of PbS crystals was closely related to the relative growth rate of the {100} and {111} faces. The Cys/Pb²⁺ molar ratios, the concentrations, and the reaction temperatures influenced the growth rate of the {100} and {111} faces, which determined the final morphology of PbS microcrystals.