Growth of PbS microtubes with quadrate cross sections

Lead sulfide (PbS) microtubes with quadrate cross section were grown by the reaction of Pb(CH3COO)2·3H2O and thiourea in ethanol at room temperature with the aid of ultrasound radiation. Crystal structure and composition of the microtubes was identified by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The morphology of the products was assessed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed that the average diameter of the tube is about 3 μm while the length is 30 μm. Based on the SEM observation of the morphology evolution, a three-stage growth model was proposed. It was found that the quadrate PbS microtubes were grown from the initial PbS nuclei (formed by the decomposition of Pb-thiourea complex) to porous spheres, and then to the final tubes. Ultrasound was found to be the key factor, the power of which induced the supersaturation and thus directly effected the formation of spherullites. These results further confirmed the proposed growth model.