Synthesis and properties of (Co, Ni) co-doped ZnS nanoparticles

Abstract

Pure and (Co, Ni) co-doped ZnS nanoparticles are synthesized by using the chemical co-precipitation method. In this process Zinc Acetate [Zn (CH₃COO)₂. 2H₂O], Sodium Sulfide (Na₂S), Nickel Chloride [NiCl₂.6H₂O] and Cobalt Acetate tetra hydrate [Co(CH₃COO)₂.4H₂O] act as precursor elements. Poly Vinyl Pyrrolidone (PVP) is used as capping agent. Pure ZnS and Cobalt doped at different concentrations (1, 3, 5 mol %) with Ni kept as constant at 3 mol % are grown. The X-ray diffraction (XRD) patterns indicate the formation of single phase cubic blended structure of pure and (Co, Ni) co-doped ZnS nanoparticles. From XRD calculations, the sizes of the pure and (Co, Ni) co-doped ZnS nanoparticles yield the range of 2 - 3 nm. The Raman peaks are observed at 263, 344 cm^-1, which are in good agreement with standard Raman transverse optical mode (TO) and longitudinal optical mode (LO), suggesting that the pure and co-doped samples have cubic blended structure. Optical absorption spectra show the absorption edge at 310 nm, in conformity with excitation and emission of PL spectra. The photoluminescence (PL) spectra exhibit the emission peaks in between 430 and 550 nm, which lie in UV and visible regions. SEM micro graphs show that the surface morphology of samples is nearly spherical; EDAX spectra depict the presence of Zn, S, Co and Ni in the chemical composition of samples in appropriate stoichiometric proportions. The micrographs recorded from Transmission Electron Microscope (TEM) show that the surface morphology of nanoparticles is spherical and average size of the nanoparticles is 15 nm. The magnetization measurements indicate the ferromagnetism in the synthesized samples at room temperature.