GREEN SYNTHESIS OF SILVER NANOPARTICLES BY THE ACTION OF BLACK OR GREEN TEA INFUSIONS ON SILVER IONS

Abstract

Silver nanoparticles were obtained by the reduction of Ag + ions through the action of black tea or green tea infusions. Also decaffeinated tea infusion is able to produce silver nanoparticles. The tea polyphenols present in the black and green tea are able not only to reduce silver ions but also to stabilize the resulting nanoparticles acting as “capping agents”. The surface plasmon resonance characteristic absorption band of silver nanoparticles was used to monitor the reduction kinetics of silver in black and green tea infusions respectively. It was found a faster reduction kinetics in green tea infusion. Dynamic light scattering (DLS) was used for the determination of the average diameter of the silver nanoparticles which were found of 20.8 nm in green tea infusion and 78.7 nm in black tea infusion. For comparison the average diameter of silver nanoparticles obtained in tannin was found at 55.7 nm. DLS was also used for the determination of the Z-potential of the silver colloidal dispersions in black and in green tea infusions. The results show that stable suspension are obtained since the tea polyphenols act also as capping and stabilizing agents of the nanoparticles. The bactericidal properties of silver nanoparticles in both black and green tea infusions were confirmed on the Gram(-) bacterium P. Aeruginosa . Instead, the silver nanoparticles in both black and green tea infusions are not effective against the spores of B. Subtilis .