| Semiconductor nanocrystals were so-called 'Quantum Dots' or 'QD', which were extensively investigated due to their high quantum yield and quantum confinement effect. Various applications of semiconductor nanocrystals include display photovoltaic devices, lasers, light-emitting diodes, solar cells and biological tagging materials. Recently with the development of nanotechnology, semiconductor nanocrystals have been paid more and more attention because of their unique optical and electronic properties. Since 1997, with the improvement of synthesis of nanocrystals, they are more and more used as biological fluorescent tags, due to their attractive qualities as fluorescent tags: broad excitation spectrum, narrow emission spectrum, precise tenability of their emission peak, longer fourescence lifetime than organic flourophores and negligible photobleaching.Recently CdSe nanocrystals are still the most extensively investigated for their successful preparation methods in controlling size, shape and monodispersity. But, on the surface of nanocrystal there are the defects unless passivated. To remove these defects, inorganic passivation has been explored in the core/shell systems such as CdSe/ZnSe, CdSe/ZnS and CdSe/CdS and shown to improve luminescence quantum yields and increase stability.Our work focused on the preparation of CdSe, CdSe/ZnSe, CdSe/ZnO nanocrystals, and try to decorate CdSe nanocrystals with mercaptoacetic acid and encapsulate QDs into silica spheres in order to transfer them into aqueous environment and use them as biological fluorescent tags. This thesis consists of four sections as follows:(1) The preparation of highly luminescent CdSe nanocrystals with a diameter from 3 to 5 nm in a mixture of TOPCK TOP and HDA.(2) Study the effecting of reaction temperature and ligands on the size of CdSe and growth rate.(3) The preparation of high quality CdSe/ZnSe core/shell nanocrystals through a 'One-pot' route for the first time.(4) Coating the CdSe core with ZnO shell materials, and improved the stability and emission efficiency greatly.(5) Capping the surface of CdSe nanocrystals with mecaptoacitic acid, and transfered them into aqueous solution successfully.(6) Preparation of water-soluble CdSe/ZnSe Quantum Dots Doped silica spheres by novel developing-film route and discussion of their properties... |
