One-step synthesis of Ag–reduced graphene oxide–multiwalled carbon nanotubes for enhanced antibacterial activities

Abstract

The present study reports a rapid one-step preparation of Ag nanoparticles decorated reduced graphene oxide–multiwalled carbon nanotube hybrids (Ag–rGO–MWCNTs) by heating a mixture of graphene oxide (GO), acid functionalized multiwalled carbon nanotubes (f-MWCNTs), and an aqueous solution of AgNO₃ in the presence of NaOH at 80 °C without the addition of any external reducing agent. The product was characterized by ultraviolet-visible spectroscopy (UV-Vis), X-ray powder diffraction (XRD), and energy-dispersive X-ray (EDX) analysis. The symmetrical shape of the UV-Vis absorption peak at 398 nm indicates the presence of small and uniform sized Ag nanoparticles in the case of Ag–rGO–MWCNTs. Moreover, the XRD peaks at 2θ = ∼38.1°, 44.2°, 64.5°, and 77.5° for the above mentioned composite suggest the formation of metallic Ag nanoparticles. The morphology of the sample was investigated using scanning electron microscopy (SEM). The SEM images reveal that there is a lower degree of curls, folds, wrinkles and aggregation in the case of Ag–rGO–MWCNTs. In addition, the antimicrobial activity of Ag–rGO–MWCNTs was examined for Escherichia coli (E. coli) and Bacillus subtilis. Positive results were obtained for E. coli only. For comparison, silver nanoparticles decorated reduced graphene oxide (Ag–rGO) and multiwalled carbon nanotubes (Ag–MWCNTs) were prepared using a similar method and after characterization, their antimicrobial activity towards Escherichia coli (E. coli) was also studied. The results indicated that Ag–rGO–MWCNTs has a superior antibacterial activity, which may be due to the synergistic effects of rGO, MWCNTs and silver nanoparticles as compared to that of Ag–rGO and Ag–MWCNTs. Moreover, the possible mechanism for the antimicrobial activity of Ag–rGO–MWCNTs has been discussed.