Role of ultrasonic irradiation and Thiourea on the synthesis of PbS nanocrystals

A noval strategy is adopted for synthesis of PbS nanocrystals via ultrasonic irradiation method underlining the effect of acoustic cavitation phenomenon on crystallinity and particle size in presence of a thiourea. X-ray diffraction (XRD) measurements have shown formation of face-centered cubic rock-salt PbS structure with enhanced crystallinity as compared to other routes. Transmission electron microscopy (TEM) images have shown particles about 5 - 15 nm range that are smaller than its Bohr Exciton radius of 18 nm. Absorption spectra have shown narrow band-edge around 275 nm that confirmed its monodispersity and blue shift in comparison to bulk PbS. Photoluminescence spectra have shown sharp emission peak at 590 nm. A probable path for its formation and chemistry is discussed to understand the mechanism of this method.