Green synthesis of iron oxide nanoparticles using Cymbopogon citratus extract and sodium carbonate salt: Nanotoxicological considerations for potential environmental applications

Abstract

Synthesis of functional and biocompatible nanomaterials, based on the green chemistry paradigm, aims to innovate by using environmentally friendly techniques. Green synthesis using natural extracts instead of chemicals is proving to be an efficient route to prepare metal and metal oxide nanoparticles. In this study, the green synthesis of iron oxide nanoparticles (FeO-NPs) is reported, using a Cymbopogon citratus (C. citratus) extract and sodium carbonate as the reducing and pH stabilizer agents, respectively. FeO-NPs are extensively studied and applied due to the exceptional physicochemical properties, outstanding the superparamagnetism, and the large surface area. These properties are corroborated using different characterization techniques, in which a regular crystal structure and the magnetic response are similar compared with FeO-NPs synthesized via the traditional methods. The presence of magnetite and maghemite (Fe3O4 and γ-Fe2O3) phases are evidenced. A major composition of Fe3O4 allows predominant superparamagnetism. However, surface functionalization reduces the spin coordination avoiding a high saturation magnetization. The presence of phytochemical content in the C. citratus allows the reduction of iron(III) to iron(II) using H+ radicals produced from hydroxyl and carbonyl groups, and the in-situ functionalization using these groups. Additionally, the biocompatibility of the FeO-NPs is evaluated performing a nanotoxicological assessment, in which Caenorhabditis elegans nematodes are used as the biological model. The presence of organic molecules on FeO-NPs promotes no toxicity and low effects on the locomotion, growth, and reproduction, suggesting a low risk using these functional nanoparticles for environmental applications, and outstanding the synthesis route with a green approach.