Alanine, aspartic acid and lactose-capped CuS, ZnS and FeS nanoparticles: synthesis, characterization and properties

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Mofokeng, Thapelo Prince
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Vaal University of Technology
Water soluble metal sulfide nanoparticles were successfully synthesized using an aqueous, simple and environmentally friendly synthetic method in the presence of ʟ-alanine, ʟ-aspartic acid and lactose, acting as both stabilizers and crystal growth modifiers. The structural and optical properties of the synthesized metal sulfide nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), Ultraviolet-visible (UV-Vis) and photoluminescence spectroscopy. Colloidal method was employed in the synthesis of CuS, ZnS and FeS nanoparticles from metal chlorides as precursors and thioacetamide (TAA) as a sulphur source. The effect of temperature on the growth and solubility of nanoparticles was investigated. The absorption spectra of all samples prepared were blue shifted as compared to their bulk materials indicating small particles size. The morphologies and sizes of the nanoparticles were influenced by the variation of temperature and capping agent. TEM images revealed interesting changes in the morphology of CuS nanoparticles formed from various capping agents. By varying the temperature, ʟ-aspartic acid-capped CuS nanoparticles changed from rod-shaped particles to particles dominated with hexagonal shape. However, the morphologies of both ZnS and FeS nanoparticles were close to spherical shape and were unaffected by either change of temperature or capping agent. Water-solubility of bio-functionalized CuS, ZnS and FeS nanoparticles was investigated. Amongst the three capping agents used, ʟ-alanine (Ala) was found to be the most effective capping agent to render solubility of the nanoparticles. As the temperature was increased, the solubility of the particles also increased. Cytotoxicity and antimicrobial activity of ʟ-alanine-capped CuS and ZnS nanoparticles were investigated. The particles were less toxic at low to moderate concentrations and only induced toxicity at higher concentrations. Particles synthesized at 95 °C were less toxic compared to other nanoparticles (35 and 65 °C) for both two set of experiments, as informed by the CC50 values. Antimicrobial properties were tested using different strains of both positive and negative bacteria and fungi. It was found that Ala-capped CuS nanoparticles were more effective against the bacteria than Ala-capped ZnS nanoparticles.
M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology
Water soluble, Metal, Sulfide nanoparticles, Metal chlorides, Thioacetamide