| Most studies in the colloidal nanocrystals have so far focused on the properties of single particle. By comparison, only in recent year, we are beginning to explore assemblies of nanocrystals, ie. nanocrystal superlattices. The exciting aspect of nanocrystal superlattice is that it is truly a new class of material, where the basic building blocks are nanocrystals instead of atoms in the traditional materials. So in principle, we can obtain many unique properties by changing the composition, the size, the shape of nanoscale building blocks and how strongly they are coupled in the assemblies. However, control the self-assembly process is a key to obtain unique properties from this new class of material. Using in-situ small angle x-ray scattering and optical microscopy, we have studied the nanocrystal superlattice formation using both colloidal droplet evaporation and Langmuir trough. We have shown that the evaporation kinetics and the concentration of ligand play important roles on the dynamics and structure of superlattices. There are also distinct differences in long range spatial coherence for arrays formed using these two techniques. This is attributed to the different dynamics that leads to the array formation. |
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