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Current efforts of nanoscale science and technology are related to the fabrication of functional materials and devices in which the individual units and their spatial arrangement are engineered down to the nanometer level. One promising way of achieving this goal is by assembling of colloidal inorganic nanocrystals as the novel building blocks of matter. This trend has been stimulated by significant advancement in the wet-chemical syntheses of robust and easily processable nanocrystals in a wide range of sizes and shapes. The increase in the degree of structural complexity of solution-grown nanostructures appears to be one of the directions towards which nanoscience will increasingly orient. The talk will highlight the recent advances in the synthesis of colloidal nanocrystals, with emphasis on the strategies developed in our group for the fabrication of colloidal nano-heterostructures, as well as on their properties and their assembly into both ordered and disordered architectures. Particular attention will be devoted to the driving forces involved in nanocrystal assembly. More specifically, we will describe a peculiar hierarchical assembly pathway followed by monodisperse colloidal octapod-shaped nanocrystals. These nanoparticles were found to self-assemble, in a suitable solution environment, in two sequential levels. First linear chains of interlocked octapods were formed, and subsequently these chains spontaneously self-assembled into three-dimensional superstructures. All the instructions for the hierarchical self-assembly are encoded in the octapod shape. We also demonstrated that the mechanical strength of these superstructures is improved by welding the constituent nanocrystals together. The sequential steps of synthesis of complex building blocks, their hierarchical assembly and their welding can be considered as a novel route towards the realization of ordered mesostructures by a completely bottom-up approach.
1. K. Miszta et al. "Hierarchical self-assembly of suspended branched colloidal nanocrystals into superlattice structures", Nat. Mater. 2011, 10, 872-876. 2. S. Deka et al., "Controlled synthesis of octapod-shaped colloidal nanocrystals of cadmium chalcogenides via "one-pot" cation exchange and seeded growth", Nano Lett., 2010, 10 (9), 3770-3776. 3. D. Baranov et al., "Chemically induced self-assembly of spherical and anisotropic inorganic nanocrystals", J. Mater. Chem., 2011, 21, 16694-16703. |
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