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Cu2-xSe nanocrystals undergo easily cation exchange reactions with
a complete retention of the anionic lattice framework. This high mobility of
cations allows for instance reversibly tuning of the value of copper
deficiency and thus the plasmonic properties of these nanocrystals. (1)
Furthermore, this mechanism can be exploited for the synthesis of
sophisticated monodisperse octapod shaped nanocrystals (2) which can be
produced in such a uniform way that they show fascinating self-assembly
behavior. (3) The ion exchange process is also reversible and can be exploited for the synthesis of otherwise inaccessible multicomponent nanoparticles with complex geometries and compositions and ordered superstructures of these nanocrystals.
The assembly of the octapod shaped nanoparticles occurs via a hierarchical mechanism via a first step of chain formation and a second step in which these one dimensional chains align into 3D assemblies. Due to this hierarchical mechanism the assemblies are not closed packed. Furthermore, it is peculiar, that even though the assembly seems to be solely driven by non-directed van der Waals interactions, the first step yields highly anisotropic assemblies (chains). The information for this type of directed assembly is encoded in the shape of the nanoparticle building block alone. (1) Dorfs, D.; Haertling, T.; Miszta, K.; Bigall, N. C.; Kim, M. R.; Genovese, A.; Falqui, A.; Povia, M.; Manna, L. J.Am.Chem.Soc. 2011, 133, 11175. (2) Deka, S.; Miszta, K.; Dorfs, D.; Genovese, A.; Bertoni, G.; Manna, L. Nano Lett. 2010, 10, 3770. (3) Miszta, K.; de Graaf, J.; Bertoni, G.; Dorfs, D.; Brescia, R.; Marras, S.; Ceseracciu, L.; Cingolani, R.; van Roij, R.; Dijkstra, M.; Manna, L. Nat. Mater. 2011, 10, 872. |
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