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SUPRANANO Report Summary

Project ID: 267129
Funded under: FP7-IDEAS-ERC
Country: France

Final Report Summary - SUPRANANO (From metal nanocrystal to supracrystal:crystallinity at nanometer and micrometer scales)

Natural systems give the route to design periodic arrangements with mesoscopic architecture using individual nanocrystals as building blocks forming colloidal crystals or supracrystals. The collective properties of such supracrystals are one of the main driving forces in materials research for the 21st century with potential applications in electronics or biomedical environments. During the project we demonstrated existence of:
- A hierarchy in the nanocrystal ordering has the following sequence: disordered assemblies, supracrystal film sitting on a disordered nanocrystal film, supracrystal films grown layer-by-layer and finally the supracrystals grown in solution with various well-defined shapes.
- Two simultaneous supracrystal growth processes from gold nanocrystal suspension, taking place in solution and at the air-liquid interface. Furthermore, the growth processes involve the crystallinity selection of nanocrystals and induce marked changes in the supracrystal mechanical properties.
- The control of the symmetry, compacity and roughness of the supracrystal surfaces remains an open question. We described the spontaneous formation of upper vicinal surfaces for supracrystals of Au nanocrystals grown on a sub-layer of ordered Co nanocrystals. Stepped or kinked surfaces vicinal to the {100}, {110} and {111} planes are observed to be extended on the micrometer range. The formation of such high index planes is explained by a heteroepitaxial relationship between both Co and Au nanocrystal.
- Formation of negative supracrystals (polyhedral holes) is attributed to inclusion in the superlattice of organic molecules.
- Hydrophobic supracrystals coated with liposomes filled by water forming a homogeneous solution. The supracrystals are considered as the supra-particles and the vesicles are defined as the supra-ligands.
- Elastic properties of supracrystals, deduced from nanoindentation measurements performed with an atomic force microscope, are related to the supracrystal growth mechanism, nanocrystallinity, interparticle distance and to the nature of the materials.
- Magnetic properties markedly depend on the nanocrystallinity.
- Vibrational properties of Au nanocrystals depend on nanocrystallinity.
- The localized surface plasmon resonance (LSPR) of noble metals markedly changes with the coating agents, the nanocrystallinity.
- The LSPR supracrystals are similar to the colloidal crystals with a shift to near infra-rouge.
- Binary systems open a new research area with formation of specific supracrystalline structures and magnetic properties.

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