Synthesis of stable sol of ZnS nanoparticles by heating the mixture of ZnS precipitate and ethylene glycol

Heating the mixture of ZnS precipitate and ethylene glycol at 328 K for 24 h formed a stable sol with homogeneous dispersion of ZnS nanoparticles. According to TEM image of the ZnS particles in the obtained sol, the average particle size was 3.8 nm. The formation process was examined by measuring the change in the UV–vis absorption spectra of the mixed solution with increases in the heating time. When the heating temperature was 408 K, the shift in the absorption edge due to the band gap transition of ZnS to a longer wavelength was observed with increases in the heating time. This shift of absorption edge indicated that the growth process occurred in the sol during the heating process. On the other hand, the qualitative analysis of the concentration of Zn2+ ions in the sol showed the presence of the dissolving process of the ZnS nanoparticles. Therefore, the dissolution–precipitation process in the mixed solution of the ZnS precipitate and ethylene glycol played an important role in the formation of the homogeneous sol.