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Chemically Engineered Nanocrystal Solids

Final Report Summary - NANOSOLID (Chemically Engineered Nanocrystal Solids)

The clear challenge in the chemistry of nanoscale materials is the rational design of a novel type of condensed matter, in which the size-tunable individual properties of nanoscale building blocks are enhanced by their interactions and by the macroscopic properties of their ensembles. The project NANOSOLID had proposed radically new strategies for the bottom-up assembly of inorganic entities of various dimensionalities into functional inorganic materials. First, novel inorganic capping ligands were introduced (such as halometalates). Subsequently, a powerful combination of chemical, spectroscopic and atomistic simulations had been applied to understand the binding motifs between the ligand and nanocrystal surface atoms. To this end, the project demonstrated the unique capability of dynamic nuclear polarization enhanced NMR spectroscopy for differentiating the core and surface atoms of nanocrystals and for probing the binding at the nanocrystal-ligand interface. Using entropy drive self-assembly and supramolecular chemistry, novel types of nanocrystal superlattices were obtained. One example is co-assembly of nanocrystals and polyoxometalate cluster. The second example is tuning of the colloidal solubility, self-organization and photoconductivity of inorganic-capped nanocrystals using host-guest complexes. The new materials design platform is presently being used in energy research, particularly in the areas of thin-film devices for cost-effective energy conversion and storage. The last two years of the project had contributed to the discovery of a new class of colloidal semiconductor quantum dots – cesium lead halide perovskite – and their detailed surface and optical characterization.