Synthesis Of Quantum Dot Microbeads Composite With Optical Gain

Nanomaterials attract extensive attention for their unique properties, among those materials, quantum dots (QDs) can be used in many fields such as bio-labeling, photoelectric device, solar cells and environmental engineering.And silica is a kind of relatively ideal carrier, which can be applied in medicine carrier, Pyrex glass, structural ceramics, chromatographic column and so on. However normal nano or micron silica spheres have relatively small particle sizes and pore sizes. Assembling very small silica nanoparticles onto big substrate to form a nano-micro composite can eventually address those issues, the composites are capable to load QDs and have potential to apply in laser emitting.This dissertation consists of three parts. In the first part, high quality QDs were synthesized by hot-injection method. Red, yellow and green cadmium selenide (CdSe) QDs were obtained by changing reaction durations, adjusting the ratio of reaction ligands and using different reactants, then grew inorganic shells onto the QDs. In the second part, the synthesis of solid and porous silica spheres has been researched. Large (above 4μm) and small (about 60nm) solid silica spheres with uniform particle size and good shape have been successfully synthesized and the synthesis of porous silica spheres based on CTAB as a template was researched. The effect of pore swelling agent 1,3,5-triethylbenzene (TMB) and additive decane has been examined and silica spheres with pore size about 4nm have been synthesized.The third part is based on the former two parts. The PS@SiO2 microbeads with large particle size and large pore size were synthesized by assembling negative charged silica nanospheres on the PDDA modified positive charged PS microbeads using layer-by-layer technology. Zeta potential, size, and morphology of the microbeads were monitored during LBL assembly process to ensure the successful deposition of silica nanoparticles. Finally, the core-shell structure microbeads with 5μm PS solid core and 350nm mesoporous shell were used to load as-prepared quantum dots (QDs), measurements show that the as-prepared core-shell microbeads can provide adequate space for QDs and may be useful to further application of nano-micro composites.