Impact of pH value on the Structural and Optical Studies of ZnS & ZnS-Ni Nano Materials

The behavior of doped and undoped nano-particles find a great deal of application in opto-electronic and semiconductor devices, so ZnS nano-crystals were grown into poly-vinyl alcohol matrix by chemical route at different wt percentage. Optical properties of both undoped and doped with ZnS nano-crystalline compounds were studied. The nano structure was characterized with the help of X-ray diffraction (XRD) and Hiresolution Transmission Electron Microscopy (HRTEM). Surface morphology was studied with the help of Scanning Electron Microscopy (SEM). Average particle size of ZnS and ZnS-Ni were found to be obtained from XRD was about 2.28 nm. Peak of Photo-luminescence (PL) emission spectra was found at 515 nm and another peak at 495 nm corresponding to dopant 0.5 % and 1.0 % at different pH value. Energy dispersive X-ray fluorescence (EDX ) spectra showed presence of Zn, S, & Ni with 67.92, 27.50 & 4.58 weight% respectively. Optical absorption with different value of pH were studied in UV-VIS Spectrophotometer and showed a strong absorbance with a tendency towards blue shift. As the value of pH decreases more blue shift occurs the particle size decreases. As the surface states are important for optical properties, at 0.5% doping with pH=3, the particle size is 2 nm which is least leads to increase in surface to volume ratio and because of it the surface states of Ni in ZnS increases which can leads to reduce the excitonic emission. Selected area electron diffraction (SAED) showed a set of three well defined rings corresponding to planes 111, 220, 311 which tallied well with the JCPDS card No. 05-0566.