Feb 27, 2009
Core-shell QDs get wet
High-efficiency II-VI QDs usually have a core-shell structure, which supplies the confinement matrix for the electrons and holes in the shell. Their applications include luminescence and display, and biological labeling and recognition. Until now, however, their syntheses have been carried out in the organic phase – the QDs are coated with a layer of surfactant molecules and therein they are insoluble in water. So the QDs can only be used in hydrophobic environments.
If they must be used in the hydrophilic phase, the QDs should be processed by surface modification, which is a prerequisite for applications in biology and biomedicine. However, this phase transfer usually results in a significant decrease in the emission quantum yield (QY). Another disadvantage is that the thick surface coating layer can dramatically increase the size of the QD composites, which can prevent their use in some applications.
CdTe QDs can be obtained in water, but their emission efficiency is susceptible to the environment, not like that of core-shell QDs. So from the CdTe QDs synthesized in water, we developed a method to grow CdSe shells on CdTe QDs in water. The resulting CdTe/CdSe core/shell quantum dots can be treated easily with bioconjugates with only a minor size expansion and tests show that folate-conjugated CdTe/CdSe QDs could enter tumor cells efficiently.
The researchers presented their work in Nanotechnology.
About the author
This work was done at the State Key Lab of CSBC and Micro-Nano Center of Hunan University at Changsha, China. Ruosheng Zeng is a PhD student in the nanophotonics group and the head of this group is Prof. Bingsuo Zou, who is also a joint professor at the Beijing Institute of Technology. Tingting Zhang is a graduate student studying for a masters degree, who did the cell labeling. Dr Jincheng Liu is an XPS expert based at the South China University of Technology, Guangzhou 510640, China. Prof. Xuanming Liu is head of the Institute of Life Sciences and Biotechnology, Hunan University, who advised the students to finish the cell labeling in his lab. Song Hu and Zhiwei Peng are two other students who helped to finish the experimental parts of this project. Dr Qiang Wan is in charge of this project in the nanophotonics group. Prof. Zou is the group leader for the project proposal, experimental design and academic completion. This work is financially supported by the NSFC of China and is a succession of a previous 973 project from the MOST (ministry of science and technology), China.