Antibacterial activities of GO–Ag nanocomposites with various loading concentrations of Ag nanoparticles

Graphene oxide (GO)–silver (Ag) nanocomposites are an up-and-coming antibacterial agent against bacteria. The antibacterial activity of GO–Ag nanocomposites depends on the concentration, particle size, and distribution of Ag nanoparticles on the GO sheets. Here, we explore the combined effect of the concentration and distribution of Ag nanoparticles on the GO sheets against the bacteria. For this purpose, three samples were prepared in such a way that the Ag nanoparticles were uniformly distributed on the GO sheets for the lowest concentration sample, but the medium concentration sample had moderate agglomeration of Ag nanoparticles, and the highest concentration sample had highly agglomerated Ag nanoparticles on the GO sheets. The particle size of Ag nanoparticles has also increased with increasing concentration of Ag. The modified Hummers method has been used to synthesize GO, and GO–Ag nanocomposites have been prepared by reducing AgNO(_3) on GO sheets at room temperature with NaBH(_4) as a reducing agent. Three different volumes of AgNO(₃) are used to vary the concentration of Ag. All the samples were tested using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), High-Resolution Transmission Electron Microscope (HRTEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analyzer (TGA). The results confirm the formation of GO–Ag nanocomposites with spherical-shaped Ag nanoparticles attached to the GO sheets. Antibacterial activities for all the GO–Ag nanocomposites were tested against the Gram-positive bacteria Bacillus subtilis using the disk diffusion method. All the nanocomposites show antibacterial activities. Our investigation established that the combined effect of concentration and distribution of Ag nanoparticles on GO sheets decides the antibacterial efficiency of the GO–Ag nanocomposites.