Alginate-mediated growth of Co, Ni, and CoNi nanoparticles:: Influence of the biopolymer structure

Biopolymers have already been widely used to control the growth of inorganic particles. However, some of these natural macromolecules present an intrinsic chemical and structural variability that may influence their templating efficiency. We have therefore compared the ability of three different sources of alginate to control the formation of Co, Ni, and CoNi nanoparticles. Variations in particle size, structure, and magnetic properties were observed depending on the alginate composition. The more stable gels allowed the formation of CoxNi100-x nanoalloys over the whole solid solution domain. Moreover, these networks stabilize Ni nanoparticles in an unusual hexagonal compact phase. These results could be related to the strength of the metal-alginate gels and hence to the metal ion coordination within the polymer network. They also point out some possible limitations in the use of natural polymers for biocomposite design.