Purification of silver and gold nanoparticles from two species of brown seaweeds (Padina tetrastromatica and Turbinaria ornata)

The present study investigated the synthesis of silver and gold nanoparticles by two species of brown seaweeds (Padina tetrastromatica and Turbinaria ornata) through analytical techniques and its antimicrobial activity. The brown seaweeds, P. tetrastromatica and T. ornata were collected from Mandabam, The collected freshly seaweeds were thoroughly washed in distilled water. About 20 grams of seaweeds were weighed with distilled water. This was boiled in hot plate at 100 0C. After reaching the boiling point of the water, the seaweed extracts were obtained in yellowish and it was stored in clean and sterile screw tubes for further studies. The color formation of silver and gold nanoparticles was confirmed by visual observation and UV-Vis absorption spectrum. The size of the nanoparticles was determined by scanning electron microscopy and dynamic light scattering. The possible group responsible for the synthesis was confirmed by FTIR. Silver and gold nanoparticles were observed for antimicrobial activity against human pathogens. Appearance of brown and ruby red color was an indication of silver and gold nanoparticles respectively and it was further confirmed by UV-Vis spectrophotometer. Scanning electron microscopy and Dynamic light scattering analysis revealed the particles with cubical shape with size of 18-90 nm for silver and 20-90 nm for gold. The silver and gold nanoparticles appeared to be associated with chemicals like as hydroxyl and carbonyl groups, probably aromatic alcohols and amines. The antibacterial activity of nanoparticles was more pronounced than antifungal activity. The work suggested a quick, easy and efficient synthesis of antimicrobial silver and gold nanoparticles by brown seaweed extracts as reducing agents.