Relationship of the nanocrystal morphology and atomistic structure with respect to the superstructure ordering within Pb
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Relationship of the nanocrystal morphology and atomistic structure with respect to the superstructure ordering within PbS- and Gold-Mesocrystals Lydia Bahrig1, Danny Haubold1, Falk Röder2, Stephen G. Hickey1, Alexander Eychmüller1 1 Physical Chemistry, TU Dresden, Bergstraße 66b, 01062 Dresden 2 Speziallabor Triebenberg, TU Dresden, Zum Triebenberg 50, 01328 Dresden ABSTRACT The relationship between nanoparticle geometry and their two dimensional assembly is investigated in order to provide insights into the three dimensional arrangement of mesocrystals. The crystal structure of the nanoparticles and their homogeneity are investigated during structure formation on the mesoscale whereby effects such as fibrillation have been observed. INTRODUCTION The manipulation of single nanoparticles is not trivial to implement in such a way as to contact them or to introduce them as functional individual units into devices. Therefore, it is currently expected that two dimensional and three dimensional arrangements will most likely be employed for applications and in this manner become an essential part of modern nanotechnology.[1] To transfer the nanoparticles into macroscopic sized materials, in such a way as to allow ease of handling and incorporation into devices using presently existing techniques, whilst at the same time maintaining their special size-tunable properties, one will need to employ arrangement methodologies such as non-classical crystallization. The small assembly units, i.e. nanoparticles surrounded by organic stabilizing ligands, can be made to spontaneously organize into periodically packed structures. Normally, direct interactions such as interparticle forces, indirect forces such as templating or external forces drive particle agglomeration where the modulation of the thermodynamic forces influences the structuring of the nanoparticle composite material by reaching different local equilibria.[2] Mesocrystals, which are crystalline materials with crystal facets of some hundred nanometers up to the micrometer size regime, form a special class of quantum dot solid. In such materials the smallest building units are normally colloidal, crystalline nanoparticles with a core-shell structure, composed of an inorganic core with an organic stabilizing shell. These building blocks are arranged in a unit cell, which forms the entire mesocrystal via a translational shift and which results in an inner crystalline structure analogous to that of single crystals. For further applications such as light emitting devices, photo detectors, thermoelectric heat-to-electricity converters, and solar cells[3] the individual nanoparticular properties are still present in addition to possible new features that derive from the unique collective properties of the arrays of ordered particles. The formation mechanism of non-classical crystallization of nanoparticular building blocks to form highly ordered architectures[4] is presently not fully understood, so that in order to create, modify and optimize materials using methodologies invo
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