Synthesis of Nanoparticles

Recently many attempts have been made to develop processes and techniques that would yield ‘monodispersed colloids’ consisting of uniform nanoparticles both in size and shape. In these systems, the entire uniform physicochemical properties directly reflect the properties of each constituent particle. Monodispersed colloids have been exploited in fundamental research and as models in the quantitative assessment of properties that depend on the particle size and shape. In addition, it has become evident that the quality and reproducibility of commercial products can be more readily achieved by starting with well-defined powders of known properties. In this way, these powders have found application in photography, inks in high-speed printing, ceramic, catalysis, and especially in medicine.

In our group, new inorganic hybrid nanoparticles integrating different materials in a core/shell structure of iron and bismuth oxides have been synthesized by a simple aqueous route. The method is based on the precipitation of an Fe(II) salt in the presence of bismuth(III) cations in a mild oxidant and leads to highly uniform and crystalline magnetic nanoparticles with sizes in the range between 8 and 30 nm. Bismuth in proportions between 1 and 20% atomic ratio of Bi to Fe acts as surfactant being accumulated at the nanoparticle surface, controlling particle size and the colloidal properties. Evidence of a core/shell structure is revealed by X-ray photoelectron spectroscopy analysis with bismuth enrichment in an outer shell. This robust material with very long chemical stability and resistance to degradation, good magnetic properties, and high density due to the presence of bismuth ions is expected to have important applications in diagnosis as a new double contrast agent for both magnetic resonance imaging and computed tomography.
“Core/Shell Magnetite/Bismuth Oxide Nanocrystals with Tunable Size, Colloidal, and Magnetic Properties”, Manuel Andrés-Vergés, María del Puerto Morales, Sabino Veintemillas-Verdaguer, F. Javier Palomares, and Carlos J. Serna. | Chem. Mater. 2012

Instituto de Ciencia de Materiales de Madrid, CSIC