水溶性CdSe/CdS量子点的合成及其与牛血清蛋白的共轭作用

用巯基乙酸(TGA)作为稳定剂，合成了水溶性的CdSe和核壳结构的CdSe/CdS半导体量子点。吸收光谱和荧光光谱研究表明，核壳结构的CdSe/CdS半导体量子点比单一的CdSe量子点具有更优异的发光特性。用TEM、电子衍射(ED)和XPS分别表征了CdSe和CdSe/CdS纳米微粒的结构、形貌及分散性。红外光谱和核磁共振谱证实了巯基乙酸分子中的硫原子和氧原子与纳米微粒表面的金属离子发生了配位作用。在pH值为7.4的条件下，将合成的CdSe和CdSe/CdS量子点直接与牛血清白蛋白(BSA)相互作用。实验发现，两种量子点均对BSA的荧光产生较强的静态猝灭作用；而BSA对两种量子点的荧光则具有显著的荧光增敏作用，存在BSA时CdSe/CdS量子点的荧光增强是不存在BSA时体系荧光强度的3倍。

Synthesis and Bioconjugates of Water-soluble CdSe/CdS Quantum Dots

A simple synthetic method was developed for the preparation of CdSe and CdSe/CdS core-shell nanoparticles by using mercaptoacetic acid as stabilizer in the aqueous system. A remarkable emission enhancement with a factor of 8 in intensity for the core-shell CdSe/CdS quantum dots was observed in comparison with that of the CdSe nanoparticles. Both optical spectroscopy and structural characterization (TEM, ED, XPS) suggested the core-shell structure of CdSe/CdS samples. The XPS data confirmed the elemental composition of the CdSe/CdS nanoparticles. Results of FTIR and 1H NMR indicated that sulfur and oxygen atoms in mercaptoacetic acid molecules took part in coordination with rich metal ions on the surface of the nanoparticles. The interaction of CdSe and CdSe/CdS quantum dots bioconjugated to BSA was also studied by absorption and fluorescence titration experiments. With addition of CdSe or CdSe/CdS nanoparticles, the fluorescence intensity of BSA was largely quenched in aqueous solutions with pH value of 7.4. However, when BSA was added to the solution of the CdSe or CdSe/CdS nanoparticle, photoluminescence intensities of two nanoparticles were dramatically enhanced, and fluorescence intensity of nanoparticles in the presence of BSA was 3 times of those nanoparticles in the absence of BSA. These results demonstrated that the BSA could modify the surface of water-soluble CdSe and CdSe/CdS nanoparticles and thereby efficiently improve the chemical stability and photoluminescence quantum yield of the nanoparticles.