Gaigalas Adolfas K, DeRose Paul, Wang Lili, Zhang Yu-Zhong
National Institute of Standards and Technology, Gaithersburg, MD 20899.
Life Technologies Corp., Eugene, OR 97402.
J Res Natl Inst Stand Technol. 2014 Dec 31;119:610-28. doi: 10.6028/jres.119.026. eCollection 2014.
Measurements are presented of the absorbance, fluorescence emission, fluorescence quantum yield, and fluorescence lifetime of CdSe/ZnS nanocrystals, also known as quantum dots (QDs). The study included three groups of nanocrystals whose surfaces were either passivated with organic molecules, modified further with carboxyl groups, or conjugated with CD14 mouse anti-human antibodies. The surface modifications had observable effects on the optical properties of the nanocrystals. The oscillator strength (OS) of the band edge transition was about 1.0 for the nanocrystals emitting at 565 nm, 605 nm, and 655 nm. The OS could not be determined for QDs with emission at 700 nm and 800 nm. The fluorescence lifetimes varied from 26 ns for nanocrystals emitting near 600 nm to 150 ns for nanocrystals emitting near 800 nm. The quantum yield ranged between 0.4 and 0.9 for the nanocrystals in this study. A brightness index (BI) was used to evaluate the suitability of the nanocrystal labels for flow cytometer measurements. Most QD labels are at least as bright as fluorescein for applications in flow cytometer assays with 488 nm excitation. For optimal brightness the QDs should be excited with 405 nm light. We observed a strong dependence of the QD absorbance at 250 nm on the surface modification of the QD.
本文给出了CdSe/ZnS纳米晶体（也称为量子点，QDs）的吸光度、荧光发射、荧光量子产率和荧光寿命的测量结果。该研究包括三组纳米晶体，其表面分别用有机分子进行了钝化、用羧基进一步修饰或与CD14小鼠抗人抗体进行了共轭。表面修饰对纳米晶体的光学性质产生了可观察到的影响。对于发射波长为565 nm、605 nm和655 nm的纳米晶体，带边跃迁的振子强度（OS）约为1.0。对于发射波长为700 nm和800 nm的量子点，无法确定其OS。荧光寿命从发射波长接近600 nm的纳米晶体的26 ns到发射波长接近800 nm的纳米晶体的150 ns不等。本研究中纳米晶体的量子产率在0.4至0.9之间。使用亮度指数（BI）来评估纳米晶体标记物用于流式细胞仪测量的适用性。在488 nm激发的流式细胞仪分析应用中，大多数量子点标记物至少与荧光素一样亮。为了获得最佳亮度，量子点应使用405 nm光激发。我们观察到量子点在250 nm处的吸光度强烈依赖于量子点的表面修饰。
