Polyethylenimine mediated silver nanoparticle-decorated magnetic graphene as a promising photothermal antibacterial agent

A novel bactericidal material, Ag@rGO-Fe3O4-PEI composite is prepared by in situ growth of silver nanoparticles onto the polyethylenimine (PEI)-mediated magnetic reduced graphene oxide (GO). The antibacterial performances of the composite are investigated by using the gram-negative bacteria Escherichia coli O157:H7 (E. coli O157: H7) as a model. The results indicate that the Ag@rGO-Fe3O4-PEI composite exhibits excellent antibacterial performance against E. coli O157:H7, with an antibacterial performance superior to those for the ever-reported photothermal materials. The bactericidal capability or the inhibition capability for bacteria growth is found to depend on the dosage of the Ag@rGO-Fe3O4-PEI and Ag/rGO-Fe3O4-PEI mass ratio within a certain range. By using a dosage of 0.1 mu gmL(-1), a killing rate of 99.9% is achieved for the E. coli O157: H7 (1 x 107 cfu mL(-1)) under a 0.5 min NIR laser irradiation (785 nm/50 mW cm(-2)). In addition, a minimum bactericidal concentration (MBC) of 0.100 mu gmL(-1) is achieved under near infrared (NIR) laser irradiation for 10 min, for which case there is absolutely no colony of E. coli O157:H7 found in the broth agar plate.