Synthesis and characterization of cobalt sulfide nanoparticles by sonochemical method

Convenient and environmentally friendly synthesis of Co9S8/PVA, CoxSy/EG and CoxSy/3-MPA nanocomposites were carried out in the presence of ultrasonic irradiation by the liquid phase synthesis of the sonochemical method. For the synthesis, cobalt acetate tetrahydrate [Co(CH3COO)2·4H2O] and sodium sulfide (Na2S·9H2O) were used as a cobalt and sulfur precursor, respectively. Polyvinyl alcohol (PVA), ethylene glycol (EG) and 3-mercaptopropionic acid (3-MPA) were used as a capping agent and surfactant. The structural, optical properties and morphology of nanocomposites were characterized using X-ray diffractometer (XRD), Ultraviolet/Visible Spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The optical band gap of Co9S8/PVA is 1.81 eV and for CoxSy/EG is 2.42 eV, where the direct band gap of bulk cobalt sulfide is (0.78-0.9 eV). The wide band gap indicates that synthesised nanocomposites can be used in the fabrication of optical and photonic devices. The growth mechanisms of the Co9S8, CoS2 and Co3S4 nanoparticles were discussed by the reactions. The effects of sonication time and annealing temperature on the properties of the nanoparticles have been studied in detail.