Crystal growth and design of various shapes of PbS micro and nanocrystals from a hydrothermal process

This paper reports on a systematic study highlighting dramatic morphological changes during the preparation of Lead Sulfide (PbS) by a hydrothermal process. PbS micro/nanostructures having different shapes and sizes were prepared via a simple hydrothermal reaction between lead acetate and a sulfur precursor (Thiourea (Tu) or Na2S). We show that the shapes of the PbS micro/nanostructures can be tuned by varying the process parameters, for instance the concentration of the precursors (lead acetate and Thiourea), the reaction time and the reaction temperature. The hydrothermal ? based PbS structures were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), High-Resolution TEM (HRTEM) and X-Ray Diffraction (XRD). We succeeded synthesizing PbS crystallites having symmetric six- and eight-arms starfish-shaped dendrites by using Thiourea (Tu) as anionic precursor. The decrease of Tu concentration as low as 0.05 M switches the crystal morphology to irregular flower- and cubic ? like shapes, while the increase of the reaction time up to 6 h leads to the formation of mono-arms dendrites. The addition of Triethylamine (TEA) to Tu in the initial reaction blocks the growth of the six-arm starfish shaped PbS crystals and leads to the formation of octahedral and sub-spherical crystals. A morphological change from starfish dendrites to crystalline nanoparticles occurs by replacing Tu by Na2S as a sulfur precursor; this transition from dendrites to nanoparticles was attributed to the nature of the anionic precursor.

Automated summary

This study reports a systematic investigation on the morphological changes of lead sulfide (PbS) during the hydrothermal preparation process. It was found that the shapes of PbS micro/nanostructures can be tuned by adjusting process parameters such as precursor concentrations and reaction conditions. Various PbS structures were characterized using microscopy and XRD, with different morphologies observed based on the choice of precursors and reaction conditions.