Effect of Reducing Agent on the Chemical Reduction Method of GO–Ag Nanocomposite and Its Antibacterial Activity

In this report, we explore the effect of the amount of the reducing agent used during the synthesis of the GO–Ag (graphene oxide–silver) nanocomposites in the chemical reduction method. We have synthesized the nanocomposites utilizing AgNO \(_{\textbf{3}}\) $_{\mathbf{3}}^{}$ as a metal precursor and NaBH \(_{\textbf{4}}\) $_{\mathbf{4}}^{}$ as a reducing and stabilizing agent. Four nanocomposites were prepared using four different weight ratios (1, 2, 3, and 4) of NaBH \(_{\textbf{4}}\) $_{\mathbf{4}}^{}$ and AgNO \(_{\textbf{3}}\) $_{\mathbf{3}}^{}$ while keeping the weight ratio of GO and AgNO \(_{\textbf{3}}\) $_{\mathbf{3}}^{}$ fixed (2). Antibacterial activity was evaluated against the Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) bacterial strains. Our results show that a moderate amount of NaBH \(_{\textbf{4}}\) $_{\mathbf{4}}^{}$ is essential to grow small-sized Ag nanoparticles (NPs) on the GO sheets. Because for a large amount of NaBH \(_{\textbf{4}}\) $_{\mathbf{4}}^{}$ , a thick layer of BH \(_{\textbf{4}}^-\) $_{\mathbf{4}}^{-}$ is present in the aqueous solution of the NaBH \(_{\textbf{4}}\) $_{\mathbf{4}}^{}$ , which reduces the interaction between the GO sheets and Ag NPs. This process increases the self-agglomeration of silver nanoparticles, preventing small-sized Ag NPs’ production on the GO sheet. The nanocomposite prepared with weight ratio 2 of NaBH \(_{\textbf{4}}\) $_{\mathbf{4}}^{}$ and AgNO \(_{\textbf{3}}\) $_{\mathbf{3}}^{}$ has the smallest-sized Ag NPs (average size of 9.15 nm), and this nanocomposite shows the highest antibacterial activity.