Effects of cyclodextrin on the morphology and reactivity of iron-based nanoparticles using Eucalyptus leaf extract

•β-cyclodextrin was used to improve the dispersion and reactivity of Fe NPs.•Fe NPs exhibited a highly efficient removal of azo-dye.•Fe NPs were characterized by various techniques.•Fe NPs were capped by β-cyclodextrin.

Plant extract is used as an eco-friendly alternative to chemical and physical methods for the synthesis of nanoparticles. Improving both the dispersion and reactivity of nanoparticles using plant extract still remains a challenge. We demonstrate a green method for stabilizing the plant-mediated synthesized iron-based nanoparticles (Fe NPs) using β-cyclodextrin (βCD). The synthesized Fe NPs exhibited a highly efficient removal of azo-dye from aqueous solution (up to 215.1 mg g−1 for Direct black G). The effect of βCD on the morphology and reactivity of Fe NPs was confirmed by various techniques, which indicated that adding βCD caused particle size to decrease from 60 to 20 nm with a narrower size distribution. It also led to changes in the surface capping of Fe NPs. We concluded that βCD not only capped the Fe NPs with a hydrophobic property, but also enhanced the water solubility of the lipophilic biomolecules due to their host-guest interaction. This process provides new insights into biocompatible cyclodextrin controlling morphology and reactivity in the green synthesis of Fe NPs.