Structural, Optical and Thermal Properties of Lead Sulphide (PbS) Nanoparticles Prepared by Chemical Route

摘要

Spherical lead sulphide (PbS) nanoparticles of different sizes have been obtained via wet solution route using different concentration of the equimolar reaction combination of lead acetate and thiourea solution prepared in methanol at room temperature. On changing the concentrationof the solution, formation of PbS nanoparticles with flowery cluster was observed. The obtained products were characterized by energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy, UV-vis-NIR visible spectrophotometerand thermogravimetric analysis (TGA). EDAX confirm purity of synthesized samples where as XRD indicates formation of PbS nanoparticles having cubic structure that contains four number of atoms per unit cell. From XRD, by employing Scherrer's formula, average crystallite size was calculatedand found to be lying between 10 nm–20 nm. The optical spectra shows blue shift in PbS samples in contrast to that of bulk PbS. The particles size calculated using absorption spectra for PbS nanoparticles lies in the range of 9 nm–10 nm. The Raman spectrum revealed the presenceof longitudinal optical phonon mode when operated with a laser of wavelength 514.5 nm suggested the existence of Fm3m (225) space group and octahedral (O h) point group thereby further confirming the formation of cubic structure of PbS. Thermal analysis indicates decomposition of materialoccur between 100 °C to 200 °C and activation energy calculated within the region of weight loss using the two different models i.e., Broido relation and Piloyan-Novikova are found to be in agreement with each other. The discussions of the above results are made in the paper in moredetailed form.