Synthesis of antibacterial and magnetic nanocomposites by decorating graphene oxide surface with metal nanoparticles

Silver is known to have inhibitory and bactericidal effects. In the present work, we have devised a facile method for the synthesis of metallic silver nanoparticles (Ag NPs) using water-soluble plant extract of cinnamon as a green reducing and capping agent. The formation of Ag NPs was confirmed by the surface plasmon resonance (SPR) absorption at 430 nm in the UV-vis spectra. Different nanocomposites of graphene oxide (GO) with both Ag and iron oxide (IO) NPs exhibiting both antimicrobial and magnetic properties were prepared and characterized by UV-vis absorption, Fourier transform infrared (FTIR) and energy-dispersive X-ray (EDX) spectroscopies, and transmission electron microscopy (TEM). The sizes of Ag and IO NPs on the GO sheet as determined from the TEM images were 20 and 5 nm, respectively. The antibacterial effects of Ag NPs and [GO + IO + Ag] nanocomposites towards both Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus were compared. The Ag NPs are mainly responsible for the antibacterial effects, although GO and IO NPs also possess antibacterial properties. The minimum inhibitory concentration (MIC) values for both Ag NPs and nanocomposites against E. coli and S. aureus were 0.025 mg ml−1 and 0.05 mg ml−1, respectively. We have also demonstrated that [GO + IO + Ag] nanocomposites are bifunctional (antibacterial and magnetic) and can be harvested with a magnet.