The Preparation of Graphene Oxide-Silver Nanocomposites: The Effect of Silver Loads on Gram-Positive and Gram-Negative Antibacterial Activities

Abstract

In this work, silver nanoparticles (Ag NPs) were decorated on thiol (–SH) grafted graphene oxide (GO) layers to investigate the antibacterial activities in Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa). The quasi-spherical, nano-sized Ag NPs were attached to the GO surface layers, as confirmed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), respectively. The average size of GO-Ag nanocomposites was significantly reduced (327 nm) from those of pristine GO (962 nm) while the average size of loaded Ag NPs was significantly smaller than the Ag NPs without GO. Various concentrations of AgNO3 solutions (0.1, 0.2, and 0.25 M) were loaded into GO nanosheets and resulted in the Ag contents of 31, 43, and 65%, respectively, with 1–2 nm sizes of Ag NPs anchored on the GO layers. These GO-Ag samples have negative surface charges but the GO-Ag 0.2 M sample (43% Ag) demonstrated the highest antibacterial efficiency. At 10 ppm load of GO-Ag suspension, only a GO-Ag 0.2 M sample yielded slight bacterial inhibition (5.79–7.82%). As the GO-Ag content was doubled to 20 ppm, the GO-Ag 0.2 M composite exhibited ~49% inhibition. When the GO-Ag 0.2 M composite level was raised to 100 ppm, almost 100% inhibition efficiencies were found on both Staphylococcus aureus (S.A.) and Pseudomonas aeruginosa (P.A.), which were significantly higher than using pristine GO (27% and 33% for S.A. and P.A.). The combined effect of GO and Ag nanoparticles demonstrate efficient antibacterial activities.

Synergistic Antibacterial Activity of Silver-Loaded Graphene Oxide towards Staphylococcus Aureus and Escherichia Coli

“…For GO-Ag NPs, the rapid and excellent antibacterial activities of the nanocomposites were attributed to the synergistic effect of GO nanosheets and Ag NPs (illustrated in Figure 10a). These results are in agreement with those of other works [38,45,61]. In TEM images of the bacterial morphology after treatment by GO-Ag NPs (Figure 7g,h), both E. coli and S. Aureus were more severely damaged as a cluster colony compared with those that received pure GO or Ag NPs treatment.…”

“…Table 3 summarizes the antibacterial effect of previously reported publications and this study. All of the reports examined the GO-Ag NPs antibacterial effect with little emphasis on the mechanism [22][23][24][25]27,28,35,36,38]. Compared with the other papers, our study has demonstrated the synergistic bactericidal activity of GO-Ag NPs.…”

“…In previous studies, we demonstrated that GO-Ag NPs exhibited good bactericidal activity by applying NaSH as the intermediate bridge to orient Ag NPs onto GO sheet. However, the mechanism has not mentioned [38]. To better understand the bactericidal activity and improve the mechanism, a novel approach to fabricate GO-Ag NPs using the reducing agent sodium borohydride and linker CS was introduced in this study.…”

Graphene Oxide–Silver Nanoparticle Nanohybrids: Synthesis, Characterization, and Antimicrobial Properties

“…It has been demonstrated that in these nanostructures GO and AgNPs work synergistically to enhance their properties, such as higher antimicrobial and catalytic activities and thermal conductivity. The synergistic properties of these hybrid materials have proven to be useful in a variety of applications (electronics, catalysis, electrochemical biosensing, drug delivery, and antimicrobial agents) [24][25][26][27][28][29].…”

Highly Efficient, Low-Cost, and Magnetically Recoverable FePt–Ag Nanocatalysts: Towards Green Reduction of Organic Dyes

“…Conventional treatment techniques to remove and decolorize organic dyes include adsorption, biodegradation, ultrafiltration, photochemical, and electrochemical methods [ 13 ]. Due to the constraints like the complex aromatic structure and recalcitrant nature of the dyes or the high operating cost, the above techniques are difficult to popularize in practical applications.…”