The effect of magnetic metal doping on the structural and the third-order nonlinear optical properties of ZnS nanoparticles.

Undoped ZnS nanoparticles and doped with selected magnetic metal ions (Fe 2+ , Co 2+ , and Ni 2+ ) have been synthesized by a solvothermal method utilizing low dopant concentrations (1%) and employing poly(vinylpyrrolidone) (PVP) as a capping agent. Cubic structure of undoped and doped ZnS nanoparticles has been observed from X-ray diffraction results. The SEM images show that the particles have smooth surface and the average grain size was found to be in range of 39–60 nm for undoped and doped ZnS nanoparticles. The optical direct band gap of undoped and doped ZnS nanoparticles have been studied using UV–vis spectra. The band gap energy value was in the range of 3.49–3.92 eV. The result of UV–vis spectroscopy shown that the absorption edge shifted to lower wavelengths with doping. The linear absorption of synthesized nanoparticles have been characterized by optical limiting (OL) method. The third order nonlinear coefficients are investigated with the help of z-scan experimental set-up using Nd: YAG laser. The samples clearly exhibit a two photon absorption effect and self-defocusing process. The results show nonlinear optical properties by doping is reduced. [ABSTRACT FROM AUTHOR]