Synthesis and studies of water-soluble Prussian Blue-type nanoparticles into chitosan beads

A new approach to the synthesis of highly stable aqueous colloids of coordination polymer nanoparticles was developed by using water-soluble chitosan beads as template and as stabilizing agent. The method consists in the synthesis of nanocomposite beads containing cyano-bridged coordination polymer nanoparticles via step-by-step coordination of the metal ions and the hexacyanometallate precursors into the chitosan pores and then water solubilization of these as-obtained nanocomposite beads. We obtain a large range of M2+/[M'(CN)(6)](3-)/chitosan (where M2+ = Ni2+, Cu2+, Fe2+, Co2+, Mn2+ and M' = Fe3+ and Cr3+) nanocomposite beads and their respective aqueous colloids containing coordination polymer core/chitosan shell nanoparticles. The nanocomposite beads and the corresponding aqueous colloids were studied by Infrared (IR) and UV-Vis spectroscopy, nitrogen sorption (BET), Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM) and magnetic analyses, which reveal the presence of homogeneously dispersed uniformly-sized cyano-bridged coordination polymer nanoparticles. The detailed studies of the static and dynamic magnetic properties of these nanoparticles show the occurrence of a spin-glass like behavior presumably produced by intra-particle spin disorder due to the low spin exchange energy characterizing these materials.