Mechanistic Insight into the One Step Green Synthesis of Hybrid rGO/Fe NPs

Abstract

Recently, the green synthesis of iron nanoparticles and associated hybrids using plant extract has attracted much attention due to its low cost, simplicity and environmental friendliness. However, the formation mechanism is still unclear. In this study, the one step green synthesis of hybrid rGO/Fe NPs by a tea extract was examined using a response surface methodology (RSM) to obtain a high activity of rGO/Fe NPs. The results showed that the best conditions for synthesis were an extract concentration = 35 g L^-1, pH = 7, and temperature = 30 °C. The optimized hybrid produced could remove 99.9% of mitoxantrone (MTX) compared to only 78.9% unoptimized. To understand it, characterizations by SEM, TEM, AFM, FTIR, XRD, Raman, and XPS showed that the Fe NPs produced had a particle size of 25 nm which were deposited randomly on the rGO nanosheet with a thickness of approximately 1.5 nm, indicating that stable hybrid rGO/Fe NPs were successfully synthesized, where the green tea extract exhibited both reducing and capping/stabilizing behavior. Furthermore, the specific biomolecules in green tea extract responsible for bio-reduction and stabilization were identified by GC-MS and LC-MS, which showed that catechins were the main reducing agents, while alkaloids, amino acids and phenolic acids were the main capping/stabilizing agents. Finally, a mechanism for synthesizing rGO/Fe NPs was proposed, where the polyphenols successfully reduced GO and complexed with iron ions to form amorphous ferric (and ferrous) polyphenol complex nanoparticles.

Keywords: adsorption, green tea, Mitoxantrone, rGO/Fe NPs, Synthesis mechanism