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Seminar | Materials Science Division

Property Control of Individual Metal Oxide Nanocrystals and their Assembled Structure

MSD Seminar

Abstract: Inorganic nanomaterials have been used in various fields based on diverse property control strategies including morphology control and defect engineering. Even their assembled structures exhibit unprecedented properties that do not exist in materials in nature.

In this presentation, the properties control of both individual nanomaterials and their assembled structure will be discussed. For the control of individual nanocrystals’ properties, we found that the size and shape of metal oxide nanocrystals can be tuned by the addition of spectator cations. The addition of spectator cation reduces the amount of byproduct water and leads to an increase in the size of nanocrystals. And the change of the polarity of the environment due to the dissociation of the spectator salt changes the shape of the resulting nanocrystals accordingly. Together with this morphology control, we found that the addition of the spectator cations affects the crystallinity of the resulting metal oxide nanocrystals. Based on this, we established a synthetic strategy to control the intrinsic defects formation in various semiconductor nanocrystals. Due to the increased ionic strength by ionized spectator metal salts and interaction with carboxylate anion in indium precursor, the metal carboxylate precursor dissociates which leads to oxygen deficiency in the final lattice.

Finally, inspired by the extrinsic defect engineering in semiconductor materials, a method to control of effective optical parameter of assembled plasmonic semiconductor nanocrystal structure is proposed. By mixing two different nanocrystals to form a two-dimensional superlattice, we observed unprecedented flattening of the effective permittivity spectrum which results in expansion of epsilon near the zero-frequency region.