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Self-assembly of CdTe QDs at the Air/Water Interface and Preparation of CdTe/Au Nanocomposite

Author: MaHongChao
Tutor: ZhengLiQiang
School: Shandong University
Course: Colloid and Interface Chemistry
Keywords: CdTe Quantum dot Urchin-like Self-assembly CdTe/Au Dumbbell-like
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 31
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Abstract

Quantum dots (QDs), known as semiconductor nanocrystals, attract extensive attention due to their unique photoluminescence property and potential application in photoconducting device and biological tag. They contain several inimitable advantages comparing with dyes, such as stable photochemical property, high fluorescence quantum yields, narrow and tunable emission peak. Despite its excellent photochemical and electrochemical properties, they are often assembled into ordered nanostructures when introduced to nanodevices. These ordered nanostructures will carry on the excellent properties of individual QDs, moreover, they will possess novel properties and perform better functions due to the interaction between the nanoparticles. In addition, as the development of the material science and technology, the single component nanomaterials cannot meet the needs nowadays, thus people begin to prepare nano-composite materials using various materials through physical or chemical method. These nano-composite materials are superior to the sigle materials, in addition, they have many unique functions that the single materials don’t possess, which will heip to get the integration of functions. For example, the nano-composite materials composed of QDs and conducting polymer can efficiently promote the separation and transmission of electrons and will further enhance the efficiency of conversion of light energy when used in solar cells. Herein, we first prepared urchin-like CdTe microspheres by the assistance of a long-chain ionic liquid C16mimBr monolayer at the air/water interface, and investigate systematically the effects of growth time and concentration of CdTe QDs aqueous solution on the formation of the urchin-like microspheres, and finally proposed a potential mechanism for the formation of the urchin-like microspheres. Furthermore, dumbbell-like CdTe/Au nano-composite materials were synthesized using Au nanoparticles and CdTe QDs, and the growth process and formation mechanism were discussed. The content of the thesis is listed as follows: (1) Formation of urchin-like CdTe microspheres by the assistance of a long-chain ionic liquid C16mimBr monolayer at the air/water interface. C16mimBr molecules were first spread onto the surface of the CdTe QDs aqueous solution, theΠ-A curve revealed that a stable monolayer was formed, which could be used for further assembly. Then the effects of growth time and concentration of CdTe QDs aqueous solution on the formation of urchin-like microspheres were studied systematically. The results indicated that the sufficient growth time was necessary for the formation of the urchin-like microspheres, as the growth time increased, the nest-like nanostructures were first formed, then flower-like nanostructures, and finally urchin-like microspheres. In addition, the concentration of the CdTe QDs aqueous solution also played a key role in the formation process. The results revealed that urchin-like microspheres could be formed only at the moderate concentration. Finally, based on the results, a potential formation mechanism of the urchin-like microspheres was proposed.(2) Dumbbell-like CdTe/Au nano-composite materials were synthesized using Au nanoparticles and CdTe QDs. The TEM and SEM images demonstrated the formation of dumbbell-like nanostructures. The EDX spectrum and the HRTEM images indicated that the as-prepared dumbbell-like nanostructures were composed of CdTe QDs and Au nanoparticles. The effect of the concentration on the morphology of the products was investigated. Finally, the mechanism of the formation of the CdTe/Au dumbbell-like nanostructures was proposed.

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