Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

Abstract

Zinc sulphide (ZnS) nanoparticles have been synthesised by a green approach involving laser irradiationof an aqueous solution of zinc acetate (Znac2) and sodium sulphide (Na2S·9H2O) or thioacetamide (TAA)in polyvinylpyrrolidone (PVP). The structural and morphological properties of the prepared sampleswere analysed using a transmission electron microscope, TEM, a high resolution transmission electronmicroscope, HRTEM, X-ray diffraction, and Raman spectroscopy. The thermal properties were studiedusing a simultaneous thermal analyser (SDTA). Better dispersed and larger particles were obtained byusing sodium sulphide (Na2S) instead of TAA as the sulphur source. X-ray diffraction (XRD) analyses andRaman measurement show that the particles have a cubic structure, which is usually a low temperaturephase of ZnS. There were phonon softening and line broadening of the peaks which are attributed to thephonon confinement effect. The average crystallite size of the ZnS nanoparticles estimated from the XRDshowed a reduction in size from 13.62 to 10.42 nm for samples obtained from Na2S, and 9.13 to 8.16 nmfor samples obtained from TAA, with an increase in the time of irradiation. The thermal stability of PVPwas increased due to the incorporation of the ZnS nanoparticles in the matrices. The absorption spectrashowed that the nanoparticles exhibit quantum confinement effects.