Algal polysaccharide capsule-templated growth of magnetic nanoparticles

Polysaccharidic alginate biopolymers have been used as templates for the controlled growth of magnetic nanoparticles. Ni2+ and Co2+ can used to form alginate gels as spherical capsules. UV-visible absorption spectroscopy allowed the investigation of the environment of the metal ions within the biopolymer network. Reduction under flowing H2/N2 led to the formation of Co and Ni nanoparticles as well as CoNi nanoalloys. Even at 350 °C, the organic matrix was partially preserved. XRD, TEM and XPS analyses were used to characterize particle structure, size and morphology. SQUID measurements indicated that all particles were ferromagnetic at 2 K. This work suggests that alginate provides a well-defined, chemically and thermally stable environment for the formation of nanoparticles, leading to magnetic nanocomposites.