Nanoparticle synthesis: size and shape control

Morphology control in the nanoscale is a hot topic because of the spectacular effects that small changes in the morphology of nanoparticles have on physical (optical, magnetic, electronic...) properties of the material. Colloidal synthesis has proven extremely useful to prepare a wide variety of nanoparticles with tight control of size and shape. Still, much of the knowledge in this area is empirical and no general rules can be provided for a rational nanomaterial design. We are particularly interested in understanding the mechanisms involved in nanoparticle growth, which determine the final size and shape. Though eminently fundamental, this research is required for the design of nanoparticle materials with tailored properties that can be used for practical applications. Of particular recent interest is the use of so-called chiral inducers to influence seeded-growth of metal nanocrystals into chiral nanostructures.

Nanoparticle Assemblies

The assembly of metal nanoparticles into ordered supercrystals can be exploited to achieve interesting collective plasmonic properties. This is particularly interesting for anisotropic nanoparticles, such as nanorods. Oriented assemblies can be obtained by slow solvent evaporation within micron sized cavities, so that the obtained supercrystals retain the shape of the templating cavities.

Nanoparticle assemblies can also be obtained in the form of well-defined clusters, which can even be maintained in colloidal dispersion. Such assemblies have been obtained by exploiting hydrophobic interactions and encapsulation with block copolymers. Such clusters can be made of identical or disimilar nanocrystals, even including multifunctionality. Additionally, the use of chiral templates leads to asymmetric suprastructures with extremely interesting optical properties.