Influences of reaction temperature, holding time and S/Zn molar ratio on structure, morphology, optical and electrical properties of ZnS nanoparticles synthesized by hydrothermal method

ZnS nanoparticles were synthesized by hydrothermal method. The influences of reaction temperature, holding time and S/Zn molar ratio on the structure, morphology, optical and electrical properties of ZnS nanoparticles were studied systematically at the range of 90 degrees C to 180 degrees C, 6h to 15h and 1:2 to 2.5:1, respectively. The results indicate that the reaction temperature, holding time and S/Zn molar ratio have no influence on phase structure. All the samples belong to zinc blende cubic structure of ZnS. However, the reaction temperature has strong influences on the growth of crystals, optical and electrical properties due to LaMer theory and two-stage growth kinetics. When the reaction temperature increases from 90 degrees C to 180 degrees C, the crystallite sizes increase from 7.0nm to 9.7nm and the average particle sizes decrease from 21nm to 14nm; the emission peaks are red shifted from 445nm to 460nm and the emission intensity is increased by 4.4 times; the dielectric constant and dielectric loss decrease from 4.86 to 4.71 and 2.86x10(4) to 2.70x10(4), respectively. While, the holding time has slight influences on the growth of crystals, optical and electrical properties. And the emission band and emission intensity of ZnS nanoparticles can be adjusted by the S/Zn molar ratio. When the S/Zn molar ratio is less than 1:1 or equal to 1:1, the emission bands range from 400nm to 600nm centered at similar to 450nm. When the S/Zn molar ratio is greater than 1:1, the emission bands range from 400nm to 700nm centered at similar to 540nm.