Investigation On Doping And Shape Control Of Oxide Nanocrystals

In this thesis, we employed zinc oxide (ZnO) based nanocrystals and tin doped indium oxide (ITO) nanocrystals as two typical examples to investigate the doping and shape control of oxide nanocrystals. Sn doped ZnO nanocrystals and ITO nanocrystals with controllable morphology and properties were successfully synthesized by an in-situ doping method in organic medium. We present the first study of cation exchange of oxide nanocrystals, demonstrating that "partial cation exchange" may be a potential doping strategy fo oxide nanocrystals.The conclusions are following:1. Sn doped ZnO nanowires with uniform diameters of 2.3±0.2 nm were synthesized based on a facile colloidal method employing an aminolysis approach. Transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Inductively coupled plasma atomic absorption spectrometer (ICP-AAS) were used to characterize the morphological and Elemental properties of the nanocrystals. Obvious blue shift in photoluminescence (PL) and UV-Vis spectra are observed, the optical energy gap may vary in the range of 3.32-3.76 eV with different doping concentration. Fourier transform infrared (FTIR) techniques were used to explore the molecular mechanism associated with the reactions. "Growth seeds" experiment demonstrates that the existence of tin dopants, which leads to of short Sn doped ZnO nanowires, is essential for the formation of ultrathin nanowires. Besides, we conducted primary experiments on Pb doped ZnO nanocrystals.2. ZnO nanocrystals with different size and crystalline features were synthesized by a high temperature alcoholysis approach and a solution method at relative low temperature, respectively. We demonstrate the cation exchange between manganese ions and ZnO nanocrystals which leads to products with tetragonal structures. We also observed a relatively slow cation exchange between magnesium ions and ZnO nanocrystals which leaded to products with poor crystallinity.3. We present the study of the effects of choices of carboxylic acid on the formation of the ITO nanocrystals. Nearly monodisperse ITO spherical nano-dots (7.6 nm±1.9 nm) and nano-flowers (18.3±2.1 nm) can be obtained via a "one-pot" approach by introducing additional 2-ethylhexanoate and n-octanoic acid (C8H16O2) respectively, owing to the different reactivities of the indium precursors. The localized surface plasmon resonance (LSPR) absorption peaks, including the wavelengths,λ and shapes of the peaks exhibit diverse features.