Effect of PVA Capping on the Optical and Structural Properties of hydrothermally synthesized ZnS Nanocrystals

The pure and PVA capped ZnS nanocrystals were synthesized by hydrothermal method using zinc nitrate and thioacetamide as the zinc source and sulphur source respectively. The XRD patterns confirmed the formation of cubic phase ZnS nanoparticles with particle sizes 32.6nm and 30.6nm respectively for the pure and PVA capped nanocrystals. The SEM micrographs show the improvement in the particle size distribution upon PVA capping. The presence of characteristic bands for the PVA in the FTIR spectrum reveals capping of ZnS nanocrystals. The strong absorption in wavelength range 263-328 nm along with a blue shift in the optical absorption edge also indicates the formation of nanocrystals. The optical gap of pure and PVA capped ZnS has been calculated using the Tauc’s relationship and blue shift in the optical gap has been reported. These results have been explained with the improvement in the passivation of surface defects for the PVA –ZnS nanocrystals.