Gold Nanoparticles Stabilized by δ‐Cyclodextrin in Aqueous Media: Characterization and Evaluation of their Catalytic Properties in the Reduction of 4‐Nitrophenol

Abstract The synthesis of gold nanoparticles stabilized by cyclomaltononaose (δ‐CD) in aqueous phase was performed. Protection of the gold nanoparticles by standard native cyclodextrins such as α‐CD, β‐CD and γ‐CD has also been considered for comparison. All of these colloidal suspensions were fully characterized by FT‐IR, DLS, UV‐Vis spectroscopy, TEM, XPS and also NMR experiments. Finally, their catalytic activity was evaluated in the reduction of 4‐nitrophenol to 4‐aminophenol in the presence of an excess of sodium borohydride. Gold nanoparticles stabilized by δ‐CD presented good activity and exhibited better long‐term stability. This study highlighted the fact that the obtention of the best catalytic activity corresponds to not only a compromise between the size of the nanoparticles and the interaction of the substrate with the metal nanoparticles surface, but also the supramolecular interactions between the substrate and the cyclodextrin.