The synthesis of citrate-modified silver nanoparticles in an aqueous suspension of graphene oxide nanosheets and their antibacterial activity.

A composite material consisting of silver nanoparticles (Ag NPs) deposited on graphene oxide (GO) nanosheets is prepared by chemical reduction of Ag metal ions by sodium borohydride (NaBH4) in the presence of trisodium citrate acting as a stabilizing agent to prevent agglomeration of the nanoparticles. The synthesized GO/Ag NPs composite was characterized by UV/vis spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM analysis confirmed a high density of Ag NPs on the GO nanosheets with a particle size range of 2-25 nm. The activity of the GO/Ag NPs suspension as an antibacterial agent against Gram positive bacteria Staphylococcus aureus and Bacillus subtilis was investigated. The percentage of the killing bacterial colonies by Ag NPs (without GO) is found to be 96-97% while 100% of killing bacterial colonies is only obtained using GO/Ag NPs suspension. Moreover, it was also observed that leakage of sugars and proteins from the cell wall of both S. aureus and B. subtilis in interaction with GO/Ag NPs suspension is higher compared to Ag NPs (without GO) and GO nanosheets.