Synthesis, Characterization, and Applications of II-VI Compound Semiconductor Nanomaterials and Superparamagnetic Nanoparticles

• Main Authors: Chih-Wei Lai, 賴志維
• Other Authors: 周必泰
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/31285317895912792184

博士 === 國立臺灣大學 === 化學研究所 === 97 === In this thesis, we concentrated on the syntheses and characterization type-II quantum dots (QDs) of various core and shell materials from II-VI compound elements by a developed soft template synthesis with surfactants, such as TOPO and HDA, on two-step approaches. In the beginning, there have a detail description of Quantum dots’ synthesis and optical property in chapter 1. Then, we have succeeded to fabricate CdSe/ZnTe, CdTe/CdSe, and CdSe/CdTe/ZnTe type-II QDs. After using chemically synthesis environment to synthesize type-II QDs, the topic what we want to research is more detail studied in fundamental approaches such as relaxation dynamics and energy/charge transfer processes. Prior to present my work, a general review in terms of chronic progress, fundamental and application of nanoscience is elaborated in chapter 2. QDs with high quantum yield, well photo-stability, and facile fabrication properties can be used for bio-sensor and bio-imaging application. We have successfully prepared highly luminescent type-I quantum dots (QDs) with narrow emission spectra. Phase transfer of the QDs from organic solvents to aqueous media was also achieved. Furthermore, the two emission wavelength (540nm and 648nm) luminescent QDs were modified 15-crown-5 ligand for detection potassium ion. recognition of K+ can be achieved via the Förster type of energy transfer between two different color QDs, so that [K+] of the order of 10-6 M can be promptly observed (chapter 3). On the other hand, for reducing toxicity of QDs, we formed QDs/SiO2 core/shell nanoparticles due to silica shell of ability to avoid the cadmium ion releasing. However, it exist lower emission intensity. To overcome this problem and practice its bio-imaging ability in vitro, we prepared QDs/SiO2 with a delay photooxidation process for enhancing QY. And it indeed worked that the QDs/SiO2 with high visible and near-infrared radiation emission intensity was not toxicity in stem cell on two-photon imaging. The practical application was also elaborated in chapter 4. In chapter 5 and 6, we then switched our gear toward the synthesis and application of superparamagnetic nanoparticles. Highly uniform Fe3O4/SiO2 core/shell nanoparticles functionalized by phosphorescent iridium complexes (Ir) have been strategically designed and synthesized. The Fe3O4/SiO2(Ir) nanocomposite demonstrates its versatility in various applications: the magnetic core provides the capability for magnetic resonance imaging and the great enhancement of the spin-orbit coupling in the iridium complex makes it well suited for phosphorescent labeling and simultaneous singlet oxygen generation to induce apoptosis. On the other hand, via a facile, we found that high pressure, high temperature, solvothermal approach makes FePt/Fe3O4 nanoparticles synthesis much more facile. Moreover, the resulting FePt/Fe3O4 MNPs possess several unique properties such as great enhancement of magnetization (e.g., ~60 emu/g at 5 kOe under applied field.), intact surface passivation and hence great dispersibility as well as the feasibility in the transformation toward water soluble MNPs. After phase transfer, the water soluble FePt/Fe3O4 MNPs have been successfully applied in MRI.