Organic-inorganic nanocomposites based on iron containing clusters and biomolecules

Biopolymers, such as the protein ferritin and the polysaccharides chondroitin sulfate and chitosan, have been used to control the nucleation and growth of nanoscale iron(III) hydroxide clusters. The biopolymers can provide nucleation sites, that in some cases are spatially defined by the shape of the polymer, and/or defined volumes within which crystal growth of the iron(III) hydroxide can proceed. The product inorganic clusters are bound to the organic polymers which both keep them in solution and prevent aggregation. The morphology of the clusters (spheres or rods) and the uniformity of their dimensions are determined by the biopolymer chosen. The temperature of formation is shown to have an effect on the structure of the clusters, a higher temperature resulting in larger inorganic clusters with a higher degree of structural order. Iron(III) hydroxide clusters in ferritin cages can be partially transformed to iron sulfide by reaction with H2S gas while remaining in the protein cage