Synthesis and Characterization of Au:Ag Nanoparticles Using Trisodium Citrate and SDS

Detergent-modified catalytic and enzymomimetic activity of silver and palladium nanoparticles biotemplated by Pyrococcus furiosus ferritin

Palladium and silver nanoparticles (NPs) anchored at the outer surface of ferritin form stable suspension of non-coated particles that possess several catalytic and enzymomimetic activities. These activities are strongly affected by detergents that significantly influence the reaction efficiency and specificity. Reductive dehalogenation of various azo dye substrates shows strong differences in reactivity for each substrate-detergent pair. Reductive dehalogenation is negatively influenced by cationic detergents while catalytic depropargylation is severely impaired by polyethylene oxide containing detergents that is an important finding in respect to potential biorthogonal applications. Moreover, Suzuki-Miyaura reaction is promoted by polyethylene oxide containing detergents but some of them also facilitate dehalogenation. Enzymomimetic peroxidase activity of silver NPs can be detected only in presence of sodium dodecyl sulfate (SDS) while peroxidase activity of palladium NPs is enhanced by SDS and sodium deoxycholate.

Chitosan stabilized Ag-Au nanoalloy for colorimetric sensing and 5-Fluorouracil delivery

Fluorescent CS/Ag-Au (chitosan/silver-gold) nanocomposite containing different weight percentage of Ag and Au was synthesized using the chemical reduction method. 5-Fluorouracil (5-FU) encapsulated nanocomposite was also synthesized and its cytotoxicity towards breast cancer cell lines (MCF-7) studied. The XRD pattern of the nanocomposite shows peaks of chitosan, silver and gold. The peaks corresponding to gold and silver indicate the face centered cubic structure of silver and gold nanoparticles. The polymer matrix nanocomposite structure with chitosan as the matrix and silver-gold as the filler phase is evident from the high resolution transmission electron microscopy (HRTEM) images and an increase in particle size from∼5nm to about 12nm is noticeable on encapsulation of 5-Fluorouracil (5-FU). The presence of fluorine in the case of 5-FU encapsulated nanocomposite and the presence of reflections corresponding to 5-FU in the SAED pattern confirms the encapsulation of 5-FU into the nanocomposite, which is also confirmed by elemental mapping. The presence of a single surface plasmon resonance (SPR) peak in the case of the nanocomposite in a position in between the SPR bands of pure silver and gold nanoparticles confirms the formation of Ag-Au alloy and the elemental mapping results obtained for the nanocomposite also supports the UV-vis results. The photoluminescence (PL) spectrum clearly shows an emission peak in the near infrared region (700-900nm), which makes the nanocomposite suitable for use in cellular imaging. The application of the nanocomposite as a colorimetric sensor was also studied and it was found to be useful for the specific detection of mercury (Hg) without much interference and the detection limit was found to be 5.0×10^-8M.