Cyclodextrin-Functionalized Iron Oxide Nanoparticles for Efficient Extractors of Gold and Silver Nanoparticles from Water

Abstract

Extraction of Au/Ag nanoparticles (NPs) as nanometallic pollutants from an aqueous phase was carried out using cyclodextrin (CD)-stabilized magnetic NPs. It was driven by the host–guest interactions operating between the hydrocarbon chains of surfactants used for the colloidal stabilization of Au/Ag NPs and CD cavity of functionalized magnetic NPs. UV–visible studies based on the surface plasmon resonance of Au/Ag NPs helped us in quantitatively measuring the extraction. Dynamic light scattering studies determined the size and zeta potential (ζ) change during the extraction. Extraction clearly turned the colored Au/Ag NPs suspension into a colorless solution, indicating the formation of a Au/Ag–magnetic NPs complex. Elemental analysis of this complex by energy-dispersive spectrometry and X-ray photoelectron spectroscopy analyses indicated the presence of a high Fe/Au or Fe/Ag atomic ratio consumed to accomplish the extraction. Results showed that extraction very much depended on the strength of inclusion complex formation between the hydrocarbon chain of the surfactant and CD cavity immobilized on the Au/Ag and magnetic NPs’ surface, respectively. Stronger host–guest interactions were required to facilitate the extraction. This unique extraction methodology based on the host–guest interactions is considered to be a much better option for cleaning contaminated water from nanopollutants than conventional filtration techniques.