Assembly Of Nanoparticles And Formation Of Composites With Conducting Polymers

Nanoparticles (NPs) have attracted much attention due to their unique optical properties, magnetic properties and catalytic properties. In recent years, various methods have been used in synthesis NPs with different sizes and morphologies. These as-prepared NPs were using as building blocks to fabricate various self-assembly structures whose morphologes looked like chain, band and sphere, through van der Waals interaction, electrostatic interaction, hydrogen bond, and so forth. These omnifarious nanostructures displayed bright prospect for applications in nano-design and nano-device.However, fragileness and aggregation were usually present in NPs and their self-assembly structures. In order to solve these problems, various functional polymers were introduced into the system. On one hand, polymers could improve the stability of NPs and their self-assembly structures. On the other hand, the existence of NPs could enhance the mechanical properties of polymers.In chapter 2, sodium citrate stabilized gold (Au) NPs were prepared. Then, TGA-capped Au NPs were prepared by ligand exchange. The self-assembly behaviors of Au NPs on substrate were carefully investigated by changing the experimental conditions such as volume ratios of water/acetone, species of ligands and temperature. With decreasing the volume ratios of water/acetone, the dendritic grade of self-assembly structures increased. When the volume ratios of water/acetone were the same, the self-assembly structures of TGA-capped Au NPs had less branches than that of sodium citrate-stabilized Au NPs. Low temperature usually increased the dendritic grade of self-assembly structure. We have investigated these self-assembly behaviors from three different aspects including interparticle interaction, the mobile rate of NPs, and the evaporation rate of the solvent. The theory explanation was quite accordance with the experimental phenomenon. Therefore, our studies were useful for understanding the complex mechanism of the self-assembly of charged NPs, and indicated a protocol to NP-based nano- or micro-structures with controlled mophologies.In chapter 3, we have successfully synthesized flower-like Au NPs using seeding approach. The results indicated dosage of hydroquinone played a key role in the formation of flower-like NPs. When the amount of hydroquinone was 100μL, no flower-like Au NPs appeared in the system. When the amount of hydroquinone and seed were 300μL and 50μL, respectively, flower-like Au NPs appeared in the system. However, further increasing the amount of hydroquinone, the size and morphology of NPs did not change. In the experiment, when the amount of hydroquinone was 1000μL, the size and morphology of flower-like NPs could be tuned through the dosage of seeds. NPs with different sizes and morphologies were also assembled on the liquid-liquid interface through reducing the surface charge of NPs. This self-assembly structure has potential application in surface enhanced Raman scattering.In chapter 4, first, we have successfully synthesized Au superparticle/polypyrrole (SP/PPy) composites. In the preparation process, poly (N-vinylpyrrolidone) (PVP) played a key role; without it, PPy could not cover on the surface of SPs and form a complete shell. The influence of pyrrole monomer concentration on the morphology and shell thickness of resulting composites was also investigated in this chapter. The experimental results indicated the optimized concentrations of pyrrole monomer ranged between 1.14 and 2.28 mM. If the concentration was too high, pure PPy NPs would appear in the system. If the concentration was too low, pyrrole monomer would polymerize into PPy antennas and randomly grow on the surface of SPs. The resulting SP/PPy composites exhibited high catalytic activity and excellent stability in the catalysis applications, for instance, the reduction of MB dye with NaBH₄. Fe₃O₄/SiO₂/PPy nanocomposites were also successfully synthesized. Magnetic nanospheres with diameter of 200 nm were synthesized via a solvothermal reaction. Then, magnetic nanospheres were coated with SiO2 shell which originated from the hydrolysis and condensation of TEOS. The thickness of SiO2 shell could be tuned by the dosage of TEOS. Subsequently, PVP was grafted on the surface of Fe₃O₄/SiO₂, which provided active sites for pyrrole monomer loading on. Finally, PPy shell formed on the surface of Fe₃O₄/SiO₂ through oxidative polymerization. The thickness of PPy shell was controllable by adjusting the dosage of pyrrole monomer. Because of the stability and biocompatibility of PPy, the Fe₃O₄/SiO₂/PPy nanocomposites showed potential applications in biomedicine.