In this paper, we have reported on biological synthesis of nano-sized silver and its antibacterial activity against human pathogens. The nanoparticles of silver were formed by the reduction of silver nitrate to aqueous silver metal ions during exposure to the extract of marine seaweed Sargassum wightii. The optical properties of the obtained silver nanoparticles were characterized using UV-visible absorption and room temperature photoluminescence. The X-ray diffraction results reveal that the synthesized silver nanoparticles are in the cubic phase. The existence of functional groups was identified using Fourier transform infrared spectroscopy. The morphology and size of the synthesized particles were studied with atomic force microscope and highresolution transmission electron microscope measurements. The synthesized nanoparticles have an effective antibacterial activity against S. aureus, K. pneumoniae, and S. typhi.
Cerium-doped zinc sulfide nanorods with flower-shaped morphology have been successfully synthesized in air atmosphere through simple chemical precipitation method. The incorporation of Ce 3? was confirmed by X-ray diffraction and energy-dispersive spectrum. The doping of Ce 3? ions has significant influence on the optical properties of the synthesized rods. UVVis absorption spectroscopy measurements have shown that the absorption peak of doped ZnS was red shifted compared to undoped ZnS. Photoluminescence measurements reveal that luminescence intensity of Ce 3? was enhanced considerably by the energy transfer from ZnS. The existence of functional groups was identified using Fourier transform infrared spectrometer. Field emission scanning electron microscope results show a uniform growth pattern of the nanorods with flowerlike structure. High resolution transmission electron microscopy results showed that the doped ZnS nanocrystals are composed of uniform nanorods with average diameter of 22 nm and length of 140 nm. The thermal stability of the nanorods was confirmed using thermo gravimetric and differential thermal analysis.
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