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Description
The solvothermal synthesis of metal sulfide nanoparticles often face challenges such as the use of toxic solvents, the complexity of multi-source precursors, and difficulties in controlling crystal phase and morphology. Castor oil, rich in hydroxylated fatty acids, serves not only as a solvent but also as a potential structure-directing agent. This study presents a sustainable solvothermal method for synthesizing cobalt sulfide nanoparticles, using castor oil as an eco-friendly solvent. The effects of two precursors, cobalt (II) bis(diethyldithiocarbamate) and cobalt (II) diethyl xanthate, on the material properties were studied. Powder X-ray diffraction (XRD) confirmed the formation of both the hexagonal (CoS) and cubic phase (Co3S4) in the cobalt sulfide nanoparticles synthesized from both precursors. Scanning electron microscopy (SEM) revealed that cobalt (II) diethyl xanthate produced nearly spherical particles and cobalt (II) bis(diethyldithiocarbamate) produced a cluster of spherical particles with some belt-like features. Fourier transform infrared (FT-IR) spectroscopy showed that castor oil molecules capped the nanoparticle surfaces, providing stabilization. Optical studies indicated band gaps of 2.60 eV and 3.58 eV for nanoparticles derived from the cobalt (II) diethyl xanthate and cobalt (II) bis(diethyldithiocarbamate) complexes respectively, highlighting quantum confinement effects. These findings underscore castor oil's dual role as both a solvent and a capping agent, illustrating how the choice of precursor and solvent influences the properties of cobalt sulfide nanoparticles for potential applications.
Keywords: Cobalt sulfide, Solvothermal synthesis, Single-source precursor, Castor oil.