Synthesis and characterisation of metal oxides nanoparticles entrapped in cyclodextrin

A new technique to prepare very small metal oxide (gamma-Fe2O3, NiO and CoO) magnetic nanoparticles is presented. Nanoparticles are prepared by addition of NaOH to a ferrous chloride solution in the presence of gamma-cyclodextrin and once formed are entrapped in the pseudosingle crystals of the oligosaccharide. The resulting crystals give diffraction pattern which looks like those of pure gamma-cyclodextrin crystals. Evidences of nanosized particles embedded in the organic crystals were obtained by HREM. The magnetic properties, investigated by ZFC-FC magnetisations, hysteresis loops and ac susceptibility measurements, deviate from those predicted on the basis of the classic single domain particles model due to the complex properties of the surface which for such small sizes, plays the major role in the total magnetic behaviour. (C) 2003 Elsevier Ltd. All rights reserved.