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

Abstract 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.