Synthesis And Characterization Of Metallic, Magnetic, Semiconductor And Silica Based Multi-functional Complex Nanomaterials

Metallic nanoparticles, semiconductor quantum dots (QDs) and magnetic nanoparticles have been acquired great attention in recent20years because of their extraordinary physical and chemical properties, and more and more synthesis methods have been explored. Their applications have also been extensively explored in various fields, such as materials, biomedical, environmental and energy technology etc. Despite the nanoparticle synthesis and application are still the hot research topics recently, people are trying to integrate the different nanomaterials attaining different properties into a nanocomposite system, which consequently will produce a nanocomposite nanoparticle possessing two or more than two functions simultaneously. These bifunctional or multifunctional nanocomposite materials hold great potential to be further explored in applications. In addition to prepare various nanoparticles in high quality, we would like to focus on the preparation of different composite nanomaterials and their characterization in this thesis. The contents of this thesis are listed as following:In chapter1, we briefly introduced the basic knowledge of noble nanoparticles, semiconductor QDs and magnetic nanoparticles, and their synthesis methods as well as their applications were also reviewed.In chapter2, we successfully prepared broad size tunable gold nanospheres and shape tunable platinum nanoparticles using a seed mediated growth method. Because of the selective suppressed growth effect to nanocrystals, gold seed with the presence of CTAB and silver nitrate would grow into a star shaped nanoparticle containing branches. We also successfully prepared silver nanocubes in ethylene glycol with the presence of PVP as surfactant and Na2S. These high quality silver nanocubes have been further scarified as template and transformed into gold nanocages, which have near infra-red extinction and pave the way for photothermal therapy in biomedical area. We explored a new method for the silica coating on gold nanoparticles, where we added MPS and TEOS together into an alkaline gold colloidal solution and allow hydrolyzation. This method will produce silica shell as well as functionalize the shell with great amount of thiol groups, which will benefit for their dispersion in an oil phased solution and the binding with semiconductor QDs. A metallic/semiconductor QDs composite nanosystem is readily prepared.In chapter3, we prepared high quality Fe3O4and size tunable γFe2O3magnetic nanoparticles through thermo-decomposition of Fe (oleate)3and Fe (CO)5. Au- heterostructure could epitaxially grow from gold seed nanoparticle by adding Fe precursor. We also investigated the effect of nanoparticle concentrations, sonic duration and surfactants to the formation of γFe2O3cluster in microemulsion system. Then, all the nanosystems, including as prepared Fe3O4,Au-Fe3O4heterostructure, yFe2O3, and yFe2O3cluster, have been coated with silica shell, which can stabilize the system as well as provide a biocompatible surface for functionalization. Then, water-soluble quantum dots could firmly self-assemble on the amine functionalized magnetic nanoparticle/silica core/shell structures, and produce bifunctional nanoprobes with magnetic and fluorescent properties, which could bring more detailed information from the tissues using the modern biomedical imaging technology.In chapter4, we firstly improved the productivity of SiO2nanotubes to10grams in a single batch through optimizing the experimental conditions. Owing to their specical geometry, silica nanotubes could not only act as carriers for drugs and nanoparticles, their biocompatible surface would also allow the easy functionalization. Both of them prove that our silica nanotubes could be used in biomedical field as the probes for targeted diagnosis and therapy. Then, these silica nanotubes could be sacrificed as template for the growth of TiO2nanotubes, which performed quite good photocatalysis effect. Finally, these silica nanotubes had been used as the template chamber for directional growth of clean gold nanorods without any surfactant, which would be poisonless to biological tissues.In chapter5, we presented a general summary of this thesis and some potential topics for future.