Studies On The Synthesis, Optical Properties And Applications Of Several Inorganic Nanoparticles

Due to their unique properties and wide potential applications,inorganic nano-materials and nano-structures attract a large number of researchers.In particular,a great deal of work focused on inorganic nanoparticles,metal nano-structures and semiconductor quantum dots recently, which including the development of synthesis methods,the study and improvement of different properties and promoting their applications to various fields.In this thesis,a lot of useful exploratory research has been done for the liquid-phase synthesis,optical properties and applications of several important inorganic nano-particles.Self-assembly of colloidal particles is one of the most effective ways to realize three-dimensional photonic crystal in optical wavelength region.Preparation of colloidal particles with high roundness,high monodispersity and narrow size distribution is the basis of this work.Basing on the traditional St(o|¨)ber method,we developed a seed-mediated method for the synthesis of SiO₂ sphere with a tunable size in the range of 100 nm to 1μm.The size distribution was less than 5%without any post treatment.Using the as-obtained SiO₂ sphere, photonic crystal films in optical wavelength region was successfully prepared:self-assembly of SiO₂ spheres at a water-air interface was designed and realized;the concept of photonic crystal fluid was proposed and successfully implemented by adjusting the ratio of SiO₂ sphere and liquid in the solution.The type of materials is expected to have further applications in the areas of chemical sensing,photonic devices and so on.Metal nanoparticles and metal nano-structures have very special optical properties owing to the surface plasmon resonance effect.Gold nanoparticles,gold nanorods and gold nanoshells are recently the research focuses in the studies of metal material synthesis and application.In this thesis,the relationship between the optical properties and the size of metal nanoparticles was firstly studied in theory.In the meantime,by using the good compatibility between gold and sulfhydryl group,gold nanoparticles were transferred to organic solution.Moreover, three-dimensional superlattice structure of gold particles was obtained by means of the self-assembly technique.This structure is expected for the future single-molecule devices and as a template for synthesizing novel nanomaterials.Secondly,we systematically studied the influence of the CTAB concentration,the amount of silver nitrate and the amount of seed gold particles on the preparation of gold nanorods by seed-mediated method.Regarding literature data and our experimental results,we first proposed that the yield and shape of gold nanorod were determined by the ratio of Ag-Br-surfactant and Ag-Cl-surfactant complexes in the growth solution.Lastly,gold nanoshell structures were synthesized with SiO₂ spheres as cores.The quantum static theory was used to analyze the optical properties of the gold nanoshells. Furthermore,in the application,we fabricated gold nanoshell arrays with colloidal crystals as templates,using layer-by-layer self-assembly technique.After etching off the SiO₂ cores by hydrofluoric acid,hollow gold nanoshell structure was obtained for the first time.This novel shell structure has great potentiality in the clinical cancer imaging and its treatment.Quantum dots(QDs),so far,have not yet widely applied in the field of biological imaging. Improvement of the stability and biocompatibility of QDs are required.Compared to the organic metal method for QDs synthesis,the water-phase synthesis method with sulfhydryl groups is more "green" and the QDs obtained can be directly applied to biological fluorescent labeling.But the disadvantage of this method is the QDs are of poor stability.Thus,the improvement and development of this water-phase synthesis method with sulthydryl groups are of great significance.In this thesis,we use mercaptosuccinicacid(/VISA),a kind of sulfhydryl molecule with low toxicity,as surfactant to develop two synthetic strategies to obtain QDs with high stability and low toxicity:(1) we synthesized CdTe QDs by hydrothermal technique.The results showed that MSA-QDs remained stable in the pH value ranging from between 5 to 11.In week acid environment,MSA-QDs were of highest stability. Moveover,QDs synthesized by hydrothermal method were more stable and less toxic than those by traditional sulthydryl water-phase method.(2) We designed and reported for the first time a novel QDs with CdTe/ZnSe core/shell structure synthesized in water-phase environment. This kind of QDs has a high quantum yield of 44%without any post treatment.Verified by testing,the core/shell QDs are of higher photostability and lower cytotoxicity comparing to CdTe QDs obtained by water-phase synthesis method.Finally,we successfully fabricated QD-IgG biological fluorescent probe by using the as-prepared CdTe/ZnSe QDs,and labeled the epidermal growth factor receptor Her2 in the human breast cancer cell line MCF7.