Contents Chapter 1 Introduction…………………………………………………1 1.1 Motivation……………………………………………………………1 Chapter 2 Background………………………………………………….3 2.1 Preparation of Uniform Particles by Wet Chemical Synthesis……….3 2.2 Introduction and Characteristics of Magnetic Nanoparticles………...5 2.2.1 Single Domain…………………………………………………….6 2.2.2 Superparamagnetism……………………………………………...7 2.2.3 Surface Anisotropy………………………………………………..8 2.3 Introduction to Iron Oxide……………………………………….......9 2.3.1 Applications of Iron Oxide………………………………………10 2.3.1.1 Drug Delivery………………………………………………...11 2.3.1.2 Separation…………………………………………………….11 2.3.1.3 Hyperthermia…………………………………………………11 2.3.1.4 Magnetic Resonance Imaging (MRI)………………………...12 2.4 Synthetic Methods of Iron Oxide nanoparticles…………………….13 2.5 Introduction to Quantum Dots………………………………………17 2.5.1 Characteristic: Quantum Size Effect………………………….…18 2.5.2 Advantages of Quantum Dots……………………………………20 2.5.3 Core-Shell structure……………………………………………...20 2.5.4 Synthetic methods……………………………………………….22 2.5.5 Applications of Quantum Dots…………………………………..23 2.6 Surface Modifications……………………………………………….25 2.6.1 Surface Modification by Adding New Materials………………...25 2.6.2 Oil-water Phases Transferring…………………………………...29 Chapter 3 Synthetic Methods and Analysis Technique……………...32 3.1 Experimental Flowchart…………………………………………….32 3.2 Synthetic Methods…………………………………………………..32 3.2.1 The Apparatus of Syntheses……………………………………..33 3.2.2 Reagent List……………………………………………………...33 3.2.3 Details of Experiment Procedures……………………………….34 3.2.3.1 Synthesis of Iron Oxide………………………………………35 3.2.3.2 Surface modification of Iron Oxide…………………………..35 3.2.3.3 Synthesis of CdSe@ZnS..........................................................36 3.2.3.4 Coupling between Iron Oxide and CdSe@ZnS........................37 3.3 Analysis Equipments………………………………………………..37 3.3.1 X-Ray Diffraction (XRD)………………………………………..37 3.3.2 Transmission Electron Microscopy (TEM)……………………...39 3.3.3 Vibrating Sample Magnetometer (VSM)……………………..…40 3.3.4 Superconducting Quantum Interference Device (SQUID)………41 3.3.5 Infrared Spectroscopy (IR)………………………………………42 3.3.6 UV-Visible Absorption Spectroscopy (UV-Vis)…………………43 3.3.7 Photoluminescence Spectroscopy (PL)………………………….44 Chapter 4 Results and Discussion…………………………………….45 4.1 Synthesis, Surface modification, and Magnetic Properties of Iron Oxide Nanoparticles……………………………………….………..45 4.1.1 Controlling Sizes of Iron Oxide Nanoparticles………………….45 4.1.1.1 Controlling the Particles’ Sizes by Changing Different Amounts of Surfactants………………………………………………..45 4.1.1.2 Controlling of Particles’ Sizes by Seed-mediated Growth…...48 4.1.2 Surface Modification of Iron Oxide Nanoparticles……………...49 4.1.3 Characterization of Iron Oxide Nanoparticles…………………...52 4.1.3.1 XRD Analyses………………………………………………..52 4.1.3.2 VSM Measurements………………………………………….54 4.1.3.3 SQUID Measurements………………………………………..55 4.1.3.4 IR Analyses…………………………………………………...57 4.2 Synthesis and Characterization of Quntum Dots (CdSe, CdSe@ZnS)....................................................................................... 58 4.2.1 PL and UV-Vis Analyses………………………………………...59 4.2.2 TEM and EDS Analyses of CdSe and CdSe@ZnS.......................61 4.2.3 PL Spetra of the CdSe and CdSe@ZnS.........................................64 4.3 Results of Coupling between Iron Oxide Nanoparticles and CdSe@ZnS Dots…………………………………………………….64 Chapter 5 Conclusions………………………………………………...69 References…………………………………………………...………….70 List of figures Figure 2.1 Mechanisms of formation of uniform particles……………………………3 Figure 2.2 Size separating process……………………………………………………5 Figure 2.3 Relations between total energy and sizes of single and multi domain…….7 Figure 2.4 Relations between grain size and coercivity………………………………8 Figure 2.5 Effects of competition between surface anisotropy (Ks) and magneto-crystalline (Ku). Ku/Ks = (a) 1 (b) 10 (c) 40 (d) 60………..……..9 Figure 2.6 Schematic representation of magnetic separation………………………..11 Figure 2.7 MRI images of cancer-targeting iron oxide nanoparticles……………….13 Figure 2.8 TEM images of 2-D hexagonal assembly of γ-Fe2O3 nanoparticles….….14 Figure 2.9 TEM images of (a) 6 nm and (b) 12nm Fe3O4 nanoparticles…………….15 Figure 2.10 TEM images of different shapes of γ- Fe2O3 nanoparticles…………….16 Figure 2.11 TEM images of Fe3O4 nanoparticles with sphere (left) and rod/wire (right) shape…………………………………………………………………...16 Figure 2.12 TEM images of large-scale synthesis of iron oxide nanoparticles. Note that the scale bar is 200nm……………………………………………...17 Figure 2.13 Schematic representation of continuous state to discrete energy states...20 Figure 2.14 CdSe evolution of photoluminescence spectra with ZnSe coating……..21 Figure 2.15 Applications of quantum dots in bioimaging…………………………...24 Figure 2.16 TEM images of Co@CdSe.......................................................................26 Figure 2.17 TEM images of (a) FePt-CdS (b) FePt-ZnS…………………………….26 Figure 2.18 TEM images of combining iron oxide nanoparticles with CdSe@ZnS...28 Figure 2.19 TEM images of (left) FePt@Fe3O4 and (right) Pt@Fe2O3 core shell structures………………………………………………………….…….29 Figure 2.20 Schematic representations of ligand exchage by (right) ionic group and (left) thiol group……………………………………………………..….30 Figure 2.21 TEM images of water-soluble particles by amphiphilic polymer wrapping on the original ones……………………………………………………..31 Figure 3.1 The apparatus of synthesis……………………………………………….33 Figure 3.2 XRD spectrometer……………………………………………………….38 Figure 3.3 The equipment of TEM…………………………………………………..40 Figure 3.4 Scheme of VSM………………………………………………………….41 Figure 3.5 figure of SQUID…………………………….……………………………42 Figure 3.6 The absorption of IR spetra………………………………………….…...43 Figure 4.1 TEM images and histogram of different amounts of surfactants (a) 3 mmole, (b) 0.3 mmole (c) 0.16 mmole, and (d) 0.08 mmole…………….47 Figure 4.2 TEM images of seed-mediated growth of iron oxide nanoparticles (a) once seed-mediated growth with size of 10.0 nm (b) twice seed-mediated growth with size of 12.3nm………………………………………………49 Figure 4.3 TEM images of different siezs of iron oxide nanoparticles after surface modification (a) 7.5 nm (b) 10.3 nm (c) 12.3 nm………………………...51 Figure 4.4 Image of water-soluble and oil-soluble iron oxide nanoparticles. The upper phase is hexane and the bottom phase is water…………………………..52 Figure 4.5 XRD spetra of iron oxide nanoparticles synthesized by seed-mediated growth with the size of (a) ~8nm (b) ~10nm (c) ~12nm. The particles are dispersed in hexane……………………………….……53 Figure 4.6 XRD spetra of iron oxide nanoparticles after surface modification for the size of (a) ~8nm (b) ~10nm (c) ~12nm. The particles are dispersed in water……………………………………………..……………………….53 Figure 4.7 Hysteresis loops of iron oxide nanoparticles with size of (a) ~8nm (b) ~10nm (c) ~12nm at room temperature. The left hand and right hand side represent before and after surface modifications………………………...55 Figure 4.8 ZFC and FC curves of (a) ~8nm and (b) ~12nm. The left hand and right hand side represent before and after surface modifications…………….57 Figure 4.9 IR analyses of (a) as-prepared and (b) DMSA coated particles………….58 Figure 4.10 Photoluminescence of CdSe dots with spectral range from different sizes. Excitation is at 366nm ultraviolet light from a hand-held UV lamp……59 Figure 4.11 PL spetra of CdSe obtained from different time intervals……………....60 Figure 4.12 UV-Vis spetra of CdSe obtained from different time intervals………....61 Figure 4.13 (a) HRTEM of CdSe with diameters around 3.3nm and (b) TEM images of CdSe@ZnS with diameters around4.1nm……………………………62 Figure 4.14 EDS spetra of (a) CdSe (b) CdSe@ZnS..................................................63 Figure 4.15 PL spetra of CdSe and CdSe@ZnS..........................................................64 Figure 4.16 TEM images of (a) magnetic nanoparticles coupling with QDs and (b) a local magnified image…………………………………………………..65 Figure 4.17 EDS spetra of figure 4.16(a)…………………………………………....66 Figure 4.18 Images of magnetic nanocomposites attracted by a permanent magnet..67 Figure 4.19 PL spectra of progression from CdSe@ZnS to FeOx+CdSe@ZnS coupling.…………………………………………...…….……………...68