ABSTRACT Synthesis and design of nanocrystalline metal oxides for applications in carbon nanotube growth and antioxidants by Seung Soo Lee Synthesis of size tunable nanomaterials creates distinct chemo-physical properties. Recently, the popularity of magnetic iron oxide and cerium oxide (CeO2) nanocrystals enables researchers to use magnetic iron oxides (magnetite and ferrites) in size dependent magnetic separation and CeO2 as an automobile exhaust gas catalyst. This research shows production of diameter-controlled monodisperse magnetic iron oxide (ranging from 3 to 40 nm in diameter) and CeO2 (from 3 to 10 nm in diameter) nanocrystals with exceptional narrow diameter distribution (σ<10%). The morphology and composition of the nanocrystals were varied by use of diverse metal precursors, reaction temperature, time, cosurfactants, and molar ratio between metal salt and surfactant. Now the narrow diameter distributions of preformed magnetic iron oxide nanocrystals made it possible to grow diameter controlled uniform CNTs. The correlation between aluminum ferrite nanocrystal diameter and CNT diameter was nearly one. Additionally, we could synthesize the highest percentage (60%) of single walled CNTs from the smallest aluminum ferrite nanocrystals (4.0 nm). Because of the synthesis of uniform nanocrystalline CeO2, we could study diameter dependent antioxidant properties of nanocrystalline CeO2; antioxidant capacity of CeO2 was nine times higher than a known commercial standard antioxidant, Trolox. In addition, the smallest CeO2 nanocrystal (4 nm) decreased the oxidative stress of human dermal fibroblasts (HDF) exposed to hydrogen peroxide. These works suggest better understanding of monodisperse nanocrystal synthetic mechanism and potential uses of the materials, such as high quality CNT growth using magnetic iron oxides as precursor catalysts and the reduction of oxidative stress in cells using monodisperse CeO2 nanocrystal as an antioxidant for reactive oxygen species in biological media. Acknowledgments I would like to thank Dr. Vicki L. Colvin, my PhD. advisor and chair of my thesis committee, for her advice, guidance, and generosity. Not only has she guided my academic career, but encouraged me to find myself and pushed me to pursue a broad range of scientific careers. I would also like to thank Dr. Robert H. Hauge, and Dr. Laura Segatori for participating as my thesis committee. I would like to thank all my past and current group members: Dr. Huiguang Zhu, Dr. John T. Mayo, Dr. Arjun Prakash, Dr. Carolina Avendaño, Dr. Denise Benoit, Dr. William W. Yu, Dr. John Fortner, Dr. Zuzanna Lewicka, Dr. Feng Li, Dr. Elizabeth Quevedo-Contreras, Dr. Chris Jones, Dr. Minjung Cho, Hema Puppala, Natalia Gonzalez-Pech, Gabriella Escalera, Dr. Qingbo Zhang, Arash Bahloul, Nasim Taheri, Daniel Garcia, Adina Boyd, Erika Bryant, Dr. Tanya Peretyazhko, Camila Zies, Aniway Lomeda, Jieying Jing, and Dr. Jing Li. I would also like to thank NSF REU student, Phuc Nguyen, who has contributed to nanocrystalline cerium oxide project. I would like to thank some of my collaborators at Rice University: Chenguang Zhang in Dr. Robert H. Hauge group, and Wensi Song in Dr. Laura Segatori group. I would also like to thank all of those at Rice University that have given me significant guidance: Teresa Champion, Dr. Wenhua Guo, Dr. Bo Chen, Dr. Angelo Benedetto, Dr. Seunghyun Lee, Sangwoo Chung, Dr. Dongsuk Shin, Dr. Hoonkyung Lee, Dr. Ji Hee Kim, Dr. Seokjin Jun, SongI Han, and Hyun Seung Yang. v I would like to thank my parents for their help, support, and constant guidance throughout my entire life. I would specifically like to thank my loving wife, Minyoung Jo, for always understanding me and for encouraging me to finish my PhD. I am so grateful for her love and patience. Contents Acknowledgments ..................................................................................................... iv Contents ................................................................................................................... vi List of Figures ............................................................................................................xii List of Tables ............................................................................................................ xix Nanocrystalline metal oxides: syntheses and applications .......................................... 1 1.1. Introduction .............................................................................................................. 1 1.2. Nanocrystal growth mechanism .............................................................................. 2 1.3. Monodisperse nanocrystal synthesis ....................................................................... 4 1.3.1. Iron oxide ........................................................................................................... 4 1.3.1.1. Synthesis of iron oxide nanocrystals ........................................................... 4 1.3.2. Cerium oxide ...................................................................................................... 8 1.3.2.1. Synthesis of cerium oxide nanocrystals ...................................................... 9 1.4. Applications of nanocrystals .................................................................................. 12 1.4.1. Iron oxide for carbon nanotube growth .......................................................... 12 1.4.2. Cerium oxide as an antioxidant ....................................................................... 15 1.5. Summary and outlook ............................................................................................ 18 Synthesis of magnetic metal oxide nanocrystals through non-hydrolytic route .......... 22 2.1. Introduction ............................................................................................................ 22 2.2. Experimental methods ........................................................................................... 24 2.2.1. Chemicals. ........................................................................................................ 24 2.2.2. Synthesis of iron oxide nanocrystals ............................................................... 24 2.2.2.1. Iron oleate synthesis ................................................................................. 24 2.2.2.2. Nanocrystals from iron oleate .................................................................. 26 2.2.2.3. Nanocrystals from the mixture of iron oleate and oleyl alcohol .............. 26 2.2.2.4. Nanocrystals from high monomer concentration .................................... 26 2.2.3. Synthesis of Ferrite nanocrystals ..................................................................... 26 2.2.3.1. Nickel, manganese, and zinc oleate synthesis .......................................... 26 2.2.3.2. Manganese iron oxide (MnxFe3-xO4) ......................................................... 27 2.2.3.3. Nickel iron oxide (NixFe3-xO4) .................................................................... 27 2.2.3.4. Zinc iron oxide (ZnxFe3-xO4) ....................................................................... 27 vii 2.2.3.5. Aluminum iron oxide (AlxFe3-xO4) .............................................................. 27 2.2.3.6. Nickel aluminum iron oxide (NiAlFeO4) .................................................... 28 2.2.3.7. Manganese zinc iron oxide (MnxZnx-1Fe2O4) ............................................. 28 2.2.3.8. Manganese aluminum iron oxide (MnAlFeO4) ......................................... 28 2.2.3.9. Manganese zinc aluminum iron oxide (Mnx-1ZnxAlFeO4) .......................... 29 2.3. Results and discussion ............................................................................................ 29 2.3.1. Diameter control of iron oxide nanocrystals ................................................... 29 2.3.2. Diameter control of ferrite nanocrystals ......................................................... 36 2.4. Conclusion .............................................................................................................. 40 Synthesis of monodisperse aluminum ferrite nanocrystals ........................................ 41 3.1. Introduction ............................................................................................................ 41 3.2. Experimental Methods ........................................................................................... 43 3.2.1. Chemicals ......................................................................................................... 43 3.2.2. Instrumentation ............................................................................................... 43 3.2.2.1. Transmission electron microscope (TEM) ................................................. 43 3.2.2.2. X-ray diffraction (XRD), and X-ray photoelectron spectroscope (XPS) ..... 44 3.2.2.3. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) ..... 44 3.2.3. Synthesis of nanocrystalline iron oxide (magnetite) ....................................... 44 3.2.3.1. Iron oxide nanocrystals prepared by Goethite (FeOOH) .......................... 44 3.2.3.2. Iron oxide nanocrystals prepared by iron oleate ...................................... 45 3.2.4. Synthesis of nanocrystalline aluminum ferrite ................................................ 45 3.2.5. Phase transfer of iron oxide and aluminum ferrite nanocrystals .................... 46 3.2.5.1. Oleic acid coated