Synthesis of wurtzite ZnS nanocrystals at low temperature

Nanocrystallites of wurtzite hexagonal ZnS have been successfully synthesized without using any capping agent by simple chemical precipitation method at a low calcination temperature of 150 A degrees C. It has been found that the size of the synthesized ZnS nanocrystallites decreases as Zn2+:S2- ratio is decreased. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption spectroscopy and M-H characteristics. The XRD patterns have confirmed that the prepared ZnS nanoparticles are of wurtzite hexagonal phase. XRD, SEM and TEM studies have shown the decrease in the particle size with the increase in S2- source. TEM images have clearly shown that size distribution of the particles lie in the range of 5-30 nm. The optical absorption bandgap of the synthesized nanocrystals has been found to be in the range of 3.69-3.74 eV. Magnetization study has shown the 'diamagnetic' behavior of synthesized ZnS nanocrystallites with a weak ferromagnetic behavior in the low field regime. The observed weak ferromagnetism has been understood due to the presence of defects in the synthesized ZnS nanoparticles.