Synthesis of cobalt-doped cadmium sulphide nanocrystals and their optical and magnetic properties

Cobalt-doped cadmium sulphide (CdS) nanocrystals (NCs) were synthesized with three different cobalt concentrations by aqueous chemical coprecipitation method. Dopant incorporation was recognised using X-ray diffraction (XRD) analysis with a shift in the diffraction peaks and compression in the lattice. The size and crystallinity of the cobalt-doped CdS NCs were studied by high resolution transmission electron microscopy (HRTEM). The blue shift in the spectra and the band gap value of Co-doped CdS NCs was estimated using reflectance UV spectrophotometer. Variation in the luminescence properties was studied by fluorescence spectroscopy. The change in the optical properties supports the Co incorporation in the CdS NCs. The BET measurement revealed that the powders had a relatively high specific surface area of 131.30, 106.93 and 102.04 m2/g for 2, 4 and 6% Co:CdS, respectively. Room temperature magnetisation was studied using vibrating sample magnetometer for both 4 and 6% cobalt-doped CdS NCs, which revealed a weak ferromagnetic signal and strong ferromagnetic hysteresis respectively.