Structural, optical and magnetic properties of cobalt-doped CdSe nanoparticles

Pure and Co-doped CdSe nanoparticles have been synthesized by hydrothermal technique. The synthesized nanoparticles have been characterized using X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Visible), photoluminescence spectroscopy (PL), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID), at room temperature. From XRD analysis, pure and cobalt-doped CdSe nanoparticles have been found to be polycrystalline in nature and possess zinc blende phase having cubic structure. In addition to this, some peaks related to secondary phase or impurities such as cobalt diselenide (CoSe2) have also been observed. The calculated average crystallite size of the nanoparticles lies in the range, 3-21 nm, which is consistent with the results obtained from TEM analysis. The decrease in average crystallite size and blue shift in the band gap has been observed with Co-doping into the host CdSe nanoparticles. The magnetic analysis shows the ferromagnetic behaviour up to 10% of Co-doping concentration. The increase of Co content beyond 10% doping concentration leads to antiferromagnetic interactions between the Co ions, which suppress the ferromagnetism.