Development of novel syntheses of nanomaterials with emphasis on composition, crystalline structure and shape.

Methods for the synthesis of nanocrystals in solution that provide the constituent atoms in such a way that they can rearrange and grow along energetically strongly favored crystalline directions. That is, to provide preferentially anisotropic and polyhedron-shaped nanoparticles with well-defined surface facets. They can also rearrange and grow in subsequent controlled stages to provide core-shell structures with particular interfaces.

 

CoO@Co3O4 octahedron-shaped nanoparticles (Nano Letters (2014), 14, 640-647).

Nanoparticles and nanocrystals can also be used as building blocks of new solids, to probe how interactions between them give rise to new collective phenomena, for example, related to magnetic exchange coupling. The interfaces established in these arrays of nanoparticles or nanocrystals offer a combination of effects depending on the local chemical composition, the crystallographic orientation, the type of coupling, and/or the 3D connectivity pattern between the transition metal oxide nanocrystals.

The interfaces are characterized by an energetic change that can become not nullified but reduced by local relaxation related to processes of diffusion and chemical ion redistribution. The correlation between chemical composition and structure considering the particularities of the nanoscale systems, taking into account ion and vacancy diffusion lengths, becomes therefore an important dynamical variable. Indeed, changes in the cationic valence state associated with changes in oxygen vacancy concentration profoundly affect magnetic, electronic and transport properties. Thus, postsynthetic modifications of preformed nanostructures for the construction of complex nanomaterials exploiting cation exchange reactions become very convenient.

Cr2O3 and Fe3O4 Hybrid Nanocomposites (Phys. Chem. Chem. Phys. (2014), 16, 22337-22342).

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