Hydrothermal synthesis and characterization of ZnS nanoparticles

Abstract

Nanostructured materials have attracted considerable interest because of their unique physical properties and potential applications in optics and electronics. Zinc sulfide is a direct wide band gap semiconductor of the II-VI group; it is used in various applications such as light emitting diodes, flat panel displays, infrared windows, solar cell [1], photocatalysis [2]. In the present work, wurtzite ZnS nanoparticles have been successfully synthesized through a surfactant free hydrothermal method with a relatively low temperature (160°C) using zinc acetate (Zn(CH3COO)2.2H2O) and thiourea SC(NH2)2 as zinc and sulfur source respectively. The reaction time was 8 hours. The obtained white powder was washed several times with deionized water and ethanol then dried at 50◦C for 2 h. On the other hand nanoparticles of ZnS were deposited on a glass substrate immersed in the autoclave. The structural characterization of the as obtained ZnS nanoparticles was carried out using X-ray diffraction (XRD) and Raman spectroscopy while the optical properties of the deposited films were investigated by ultraviolet and visible absorption spectroscopy (UV-vis). The XRD results reveal that the ZnS nanoparticles exhibit the hexagonal wurtzite structure. The broad diffraction peaks profile indicates a low dimension of the ZnS crystallites. The average size of the ZnS crystallites was estimated using the Debye–Scherrer formula; it was found to be about 13 nm.The as prepared ZnS films exhibit a strong absorption in the UV range. The band gap of the as obtained ZnS nanoparticles was estimated to 3.7 eV; this indicates that the ZnS samples exhibit a quantum confinement effect with a blue shift in the band gap with respect to bulk ZnS. The Raman spectroscopy reveals vibrational modes which are specific to wurtzite structure of ZnS that confirms the XRD results