Case Studies in Chemical and Environmental Engineering (Dec 2024)
Evaluation of green-synthesized silver nanoparticle-loaded graphene oxide (AgNPs@GO) nanocomposite toward bio logical wastewater filtration
Abstract
Although silver nanoparticles have long attracted scientists due to their remarkable antibacterial properties, the tendency of AgNPs to agglomerate results in diminished antibacterial activities and increased toxicity against normal cells. Among carbon-based nanomaterials, graphene oxide (GO), the oxidized form of graphene, can be utilized as a base for AgNPs to grow and disperse. Regarding the chemical approach, it is conventional to engage sodium borohydride (NaBH4) or hydrazine to reduce silver ions. However, using excessive amounts of these chemicals raises concerns about toxicity in biomedical applications and environmental issues. Here, this work report the synthesis of AgNPs@GO nanocomposites by reducing silver nitrate on GO using various green reducing agents, including ascorbic acid, Houttuynia cordata Thunb. leaf extract, Coffea robusta L. Linden (Robusta green coffee) bean extract, and Camellia sinensis (L.) Kuntze (green tea) leaf extract. The synthesized AgNPs@GO were characterized by X-ray diffraction spectrum, UV–Vis analysis, and dynamic light scattering, followed by an evaluation of the antibacterial activity using the diffusion agar method. The results demonstrate the high potential of green tea as a green-reducing agent in the synthesis procedure of AgNPs. The synthesized AgNPs@GO using green tea extract showed a similar UV–Vis spectral shape compared to the AgNPs@GO synthesized using NaBH4 with the maximum absorption wavelengths of AgNPs at 428 nm and GO at 203.5 nm. The AgNPs@GO synthesized also had the smallest average diameter (609.67 nm) and the highest magnitude of the zeta potential (29.83 mV) among all synthesized samples. Noteworthy is that AgNPs@GO synthesized with green tea extract demonstrated significant stability over 40 days. Furthermore, the results of the antibacterial experiments reveal that the diameter of the inhibitory zone was approximately 2 mm, half that of the control drug amoxicillin (1 mg/mL). In summary, green tea leaf extract emerged as the most effective reducing agent for the eco-friendly synthesis of stable and durable AgNPs@GO. This indicates a suitable and straightforward process for large-scale antibacterial production with potential applications in biological wastewater treatment.
