Synthesis and self-assembly of indium oxide-based semiconductor nanocrystals

Transparent conducting oxides (TCOs) have attracted extensive attention for decades due to their remarkable applications in optoelectronic devices. Recently, nanoscience and nanotechnology have infused new energy into the exploration of nanosized TCOs and their novel properties. Indium oxide (In 2O3)-based TCOs are the most important materials used in flat-panel displays (FPDs) and solar cell substrate coatings. The objective of this dissertation is to synthesize nanoscale In2O3-based TCOs with uniform size and shape using a wet-chemistry approach for the applications in optoelectronic devices and self-assembly superlattices. Self-assembly superlattices of both cubic phase In2O3 (c-In2O3) nanoctahedra single component and c-In2O3 nanoctahedra/palladium (Pd) nanospheres binary components were also investigated.;As the most widely used TCO, indium tin oxide (ITO) nanocrystals (NCs) with high crystalline and homogeneity were successfully synthesized using a facile nonaqueous method. Their average particle sizes decrease with increasing the SnO2 content. Moreover, the photoluminescence (PL) emission intensity enhances with increasing the SnO2 content in the ITO NCs. The emission mechanism of ITO NCs was also studied. In addition to ITO NCs, Europium (Eu)-doped c-In2O3 NCs were also prepared in a noncoordinating solvent. The linear electrogyration (LEG) property of Eu:In2O3 NCs incorporated in a photopolymer oligoetheracrylate (OEA) was investigated in the excitation of circularly polarized bi-color coherent beams. The LEG values of prepared nanocomposite specimens increased with the increase of Eu in the Eu:In2O3 NCs until 2.5 at% was reached, and then decreased. The LEG kinetics and the temperature dependence of the LEG effect were discussed as well.;Based on the synthesis of high quality c-In2O3 NCs, an extensive research on the one-pot synthesis of reverse type-I In 2O3 In2S3 core-shell NPs was carried out for the first time. Carbon disulfide (CS2) was used as a reducing agent and sulfur source to conduct the reduction and sulfidization processes in the same flask. The PL mechanism in the core-shell NCs was explored.;Homogeneous c-In2O3 nanoctahedra are ideal nonspherical building blocks for assembling nanocrystal superlattices which possess unique properties that are unlike small molecules and bulk crystals. Three-dimensional (3D) assemblies of c-In2O3 NCs with octahedral shape were obtained and analyzed in research for this dissertation. Besides the above superlattices from the single c-In2O3 NC component, binary nanocrystal superlattices ensembled from octahedral c-In2O 3 NCs and spherical Pd NCs were investigated for the first time. Three types of c-In2O3 skeleton structures with different assembly patterns were also identified. After examination with the electrophoretic mobilities and 3D tomographic reconstruction, the interaction between the opposite electrical charges was found to be the main driving force for binary self-assembly of c-In2O3 nanoctahedra and Pd nanospheres. In summary, the investigation of nonspherical super crystal systems provides an alternate direction in research that may extend the interest in superlattice study to a broad spectrum by enriching and varying the shape of elemental building blocks. This may potentially result in new concepts and more challenging applications such as soft X-ray photonics.