Synthesis And Properties Research Of High Quality Quantum Dots

Recent years, the scientific community has developed a variety of semiconductor nanocrystals with excellent performance (including alloy nanocrystals, core/shell structure nanocrystals, doped nanocrystals). However, the current research trend is toward the direction of environmentally friendly, cost savings, operating simple. As the synthesis technology of semiconductor nanocrystals is becoming mature, the mainstream trend is gradually toward the use of low-cost and non-toxic compounds.With different methods we synthesize core/shell structured nanocrystals CdSe/CdS/ZnS and doped nanocrystals Mn:ZnS. The preparation of CdSe core does not involve highly toxic and expensive substances such as alkylphosphine (TOP, etc.) which is used as solvent in most approaches. During the CdS and ZnS shell growth process on the CdSe core, a kind of common commercial single molecule precursor CDC(cadmium diethyl dithiocarbamate) and ZDC(zinc diethyl dithiocarbamate)are used instead of the toxic organic metals, such as bis(trimethylsilyl)sulfide and diethyl zinc. In the experiment, not only operation is more simplely, but also the fluorescence quantum yield of CdSe/CdS/ZnS nanocrystals is high (up to 90% in organic phase, and up to 60% in the water phase through the MPA ligand exchange). Doped nanocrystals Mn:ZnS is prepared by nucleation-doping method. The fluorescence quantum yield of Mn:ZnS nanocrystals is up to 54%. The results show that prepareing the smallest size of MnS nucleus is a critical factor. Through the use dodecanethiol as ligand which have the relatively weak coordination ability, a suitable reaction temperature and the right Mn:S ratio, we can control the size of MnS core. As a result, the Mn emission intensity can be enhanced. What's more, by studying the spectral characteristics we inferred the formation mechanism of CdSe/CdS/ZnS and doped nanocrystals Mn:ZnS, and characterize the structure of the product by TEM, XRD and other testing methods.