Synthesis And Water-soluble Modification Of Quantum Dots

Semiconductor quantum dots (QDs) are a kind of clusters with the size of 1~100nm. The physical behavior of the zero dimension system is similar to that of an atom; therefore, semiconductor quantum dot is also called'artificial atom'. They can emit fluorescence,just like some macromolecules, such as polycyclic aromatics. Compared to the organic dyes,QDs have the advantages of narrow emission spectrum ,size-tunable highly stable photoluminescence and biocompatibility. And a single wavelength can be used for simultaneous excitation of different-colored quantum dots.Recently, QDs have been widely applied in biological labels, fluorescent markers, immunoassay, fluorescence imaging and drug delivery due to their excellent optical properties. In this paper, QDs with high quantum yield and good monodispersity were prepared by improved'green chemosynthesis'in organic system. The influence of reaction time, temperature and solvent on the growth and performance of QDs was discussed. And then, the ligand was replaced with water soluble macromolecule polymer for the modification of QDs. And it enabled QDs to be possible application in the field of biomedicine.(1) In the first chapter of the article, large-scale CdSe quantum dots with high fluorescence intensity and good monodispersity were prepared, using diesel oil as solvent , and oleic acid as ligand, instead of violently poisonous TOPO. It could provide a great prospect of industrialized production of QDs.(2) In the second chapter, uniform CdTe quantum dots with high fluorescence intensity and good monodispersity were prepared under a low temperature (80-160℃) condition, using caprylic acid and TOPO as ligand, diesel oil as solvent. Interestingly, the emission spectrum of CdTe quantum dots exhibited large blue shift phenomenon under the visible light condition. However, when CdTe quantum dots were modified with mercaptoacetic acid, and successfully transfered from oil phase to water phase, the emission spectrum exhibited large red shift phenomenon under the visible light condition.(3) In the third chapter, using the CdSe quantum dots prepared in the first Chapter as the core, CdSe/ZnS and CdSe/CdS core-shell quantum dots were synthesized by SILAR method. The core-shell quantum dots modified with the synthesized polymer ligand were transferred from oil phase into aqueous phase successfully.