Structural and optical properties of solvothermally synthesized ZnS nano-materials using Na2S center dot 9H(2)O and ZnSO4 center dot 7H(2)O precursors

Abstract

Hexagonal wurtzite (HWZ) ZnS nanorods were formed in specimens with a S/Zn ratio of 1.3, synthesized at temperatures >= 200 degrees C in a solution containing 80 vol% water and 20 vol% of ethylenediamine (EN). In contrast, HWZ ZnS nanoparticles were formed in specimens synthesized at temperatures lower than 200 degrees C. Also, cubic zinc blende (CZB) ZnS nanoparticles were formed in specimen synthesized in water. The absorption peak for the HWZ nanorods and CZB ZnS nanoparticles was at wavelength of 325 nm and 339 nm, respectively, indicating that the band gap energy of the former is larger than that of the latter. Moreover, the HWZ ZnS exhibited two emission peaks at 474 nm and 580 nm. The peak at 474 nm is attributed to Zn vacancies but the origin of the peak at 580 nm remains undetermined. Since the intensity of the emission peak at 580 nm was significantly higher for the HWZ nanoparticles than for nanorods, this peak might be associated with defects in the HWZ ZnS nanoparticles. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.