Studies on the Influence of Thiol-Functional Ionic Liquids on CdSe Quantum Dots
|Course||Physical and chemical|
|Keywords||Quantum Dot CdSe Thiol ligand Functional ionic liquid Photostability|
Quantum dots (QDs) are considered to be the good semiconductor nanocrystals, and currently have become a research focus over the scientific and technological fields. Because of the inimitable qualities of light and size dependence, QDs can be widely used in biomedical, optoelectronic devices, and some aspects of analysis and detection. However, there are a few researches on surface properties and stability of QDs up to now, which is great significance to the practical applications. Supported by the National Natural Science Foundation of China (21073055), this work reports the effects of UV irradiation on the stability of ionic liquid-capped CdSe QDs, and the major contents are as follows:1. CdSe QDs are synthesized by the modifying method of high temperature injection, in which the synthesis conditions, such as temperature, time, the molar proportion of selenium and cadmium, are optimize to obtain the QDs with high quality. Using octadecyl amine (ODA) as the surface coating agent of CdSe QDs, it is shown that the optimal synthesis conditions include: the injection temperature at 280℃, growth temperature at 240℃, reaction time during 3 ~ 5min, the proportion of cadmium and selenium between 1:5 to 1:10. both UV and fluorescence technologies are used to characterize the properties of CdSe QDs, and the results show that the as-synthesized QDs with narrow size distribution, good dispersion, high quantum yields, and more are very stable in hexane, chloroform and other non-polar solvent.2. The functionalionic liquids, both [C4mim-SH]Br and [C10mim-SH]Br, are synthesized through three reaction steps. The thiol (-SH) in the ionic liquids is considered the functional group that most likely combines with CdSe QDs. The highlight of this paper is use the ionic liquids to replace the ODA on the CdSe by the process of ligand exchange, and this makes the as-synthesized QDs to be transferred from the organic phase into the aqueous phase.3. Adding the ionic liquid containing thiol into the solution of ionic liquid-capped CdSe QDs, the dispersion stability of CdSe QDs under UV irradiation is researched by means of the measurements of dynamic light scattering, Zeta potential and UV-Vis spectrum. With the increase of the ionic liquid concentration and the length of alkyl side chain, the experimental results show that the size distribution, Zeta potential and stability of CdSe QDs will be enhanced over a certain concentration range of ionic liquid. When the excess of the ionic liquid in the solution is more than a certain level, the dispersion stability can be reduced. The difference of stability results from two changes during the UV irradiation. If we want to improve the stability of CdSe QDs, therefore, we must prevent the occurrence of photooxidation, add the excess ionic liquids, and change the alkyl side chain length in ionic liquids.