Liquid Phase Synthesis Of Magnetic, Gold And Titanium Dioxide Nanoparticles

The methodology study on nanosized materials has received significant progresses in the past ten years. Particularly, regarding the synthetic methods for nanoparticles, wet chemical process has been one of the most important methods. The wet chemical method involves the chemical reaction, in which the dissolved metallic compounds are reduced or precipitated into undissolved solid particles in a small size. The method usually has a high yield for production of high quality nanoparticles and is capable of producing many kinds of nanoparticles. This thesis addressed the recent progresses of wet chemical synthesis of nanoparticles and studied the synthetic methods of iron oxide, gold and titanium dioxide nanoparticles. The details are shown as follows:1) The thermal decomposition of metallic organic compounds in a high boiling point solvent may produce high quality nanoparticles. This method was studied in this thesis for synthesize magnetic nanoparticles. The effects of surfactants and solvents were investigated during the synthesis. The size and shape of magnetic nanoparticles were controlled by changing concentration of surfactants and reaction temperature. TEM, XRD, VSM, UV-vis were used for characterizations of magnetic nanoparticles.2) A facile synthesis of high quality gold nanoparticles is developed and introduced here. Take an inside view of the typical two phase method, it can be found that the key factor for producing uniform sized gold nanoparticles is the thermal treatment after synthesis. Removing solvent and heating thiol capped gold nanoparticles will result in a shape and size evolution of gold nanoparticles toward high uniformity. This result indicates that the synthetic method for thiol capped gold nanoparticles can be varied to many. Based on this principle, a step-by-step method is developed to produce high quality gold nanoparticles. This method only uses three chemicals and can be performed easily. By controlling the concentration of gold nanoparticles, 2D and 3D close packing structures were observed in as-prepared gold nanoparticles.3) Using seed mediated method produced gold nanorods with different aspect ratio in aqueous solution. The aspect ratio of gold nanorods is controlled by varying seeding amounts. In general, more seeds were added into growth solution, smaller aspect ratio is obtained. TEM, SEM, XRD, and UV-vis are employed to characterize gold nanorods and self-assembly structures. It is observed that the capillary force between nanorods plays an important role in the formation of highly ordered packing structures. The gold nanorods prefer to align side by side to form a ribbon-like structure. Due to the shape effect, the nanorods separate automatically from the mixture of nanorods and nanospheres.4) Titanium dioxide nanoparticles and nanotubes are prepared by wet chemical methods. The titanium dioxide nanostructures were further modified by doping transition metal ions to improve its Photocatalytic activity. The transition metal ions act as a charge separation center to trap the electrons on the surface of titanium dioxide and help catalyst improve its catalysis efficiency.