Preparation And Photoluminescence Study Of Nanoparticles And Their Composite Structures

Metal-dielectric-semiconductor composite structures have shown attractiveapplication prospect in the nonlinear optical devices, catalysis, electroluminescentdevices, and biomarker. Au NPs have been widely used for biological location andbiomarker, the storage and transmission of energy, surface enhanced spectroscopy, etc.But Au NPs are prone to the phenomenon of agglomeration, in order to solve thisproblem, a thin SiO₂dielectric layer has been coated on the surface of the Au NPs,which can greatly improve its stability. CdTe QDs belong to the II-VI semiconductor,which have been widely applied in biological fluorescence labeling. So, it isimportant to enhance the fluorescence properties of CdTe QDs in the field ofbiological science. This article mainly investigated the Au-SiO₂-CdTe hybird structurecomposed of Au-SiO₂core-shell NPs which decorated with CdTe quantum dots （QDs）and used the local surface plasmon resonance of Au NPs to improve the fluorescentproperties of CdTe QDs in aqueous solution. Meanwhile, we have discussed theinteraction mechanism between the plasmon of the metal and exciton of thesemiconductor. The emission efficiency of the composite structure can be usuallytuned by controlling the sizes of the metal particles and the thickness of the dielectriclayer between the semiconductor and the metal. The detailed contents of thisdissertation can be summarized as follows：（1） Au NPs with different sizes were synthesized via sodium citrate reduction.The absorption peaks of the as obtained Au NPs have slight change due to thedifferent particle sizes. Then the surfaces of these Au NPs were modified by（3-aminopropyl）trimethoxysilane （APTMS）. By using modified St ber method, AuNPs were coated with a layer of SiO₂to form Au-SiO₂core-shell structure. Variousfactors affecting the size of the Au NPs and the coating thickness of SiO₂, and itscorresponding UV-absorption were analysized.（2） CdTe QDs with good crystallinity and well fluorescent performance weresynthesized successfully using thioglycolic acid as a modifier in aqueous solution.The influence of different pH conditions on the fluorescent properties of CdTe QDswas studied. It was found that the fluorescence efficiency of CdTe QDs is the bestonly when pH=8.0.（3） Using APTMS again to make Au-SiO₂core-shell structure surface modification, and then CdTe QDs were coated to form Au-SiO₂-CdTe hybird structure.The coupling effect between the surface plasmons generated in the metal NPs and thesemiconductor exciton was further studied in the Au-SiO₂-CdTe hybird structure. TheAu NPs plasma related photoluminescene properties of the Au-SiO₂-CdTe hybridstructure were studied by the fluorescence spectrophotometer.