School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel.
ACS Nano. 2011 Nov 22;5(11):9034-43. doi: 10.1021/nn203234b. Epub 2011 Oct 12.
The synthesis of chiral penicillamine-capped CdS and CdSe quantum dots (QDs) was adjusted to control the size of the nanoparticles. This, together with size separation, allowed for simultaneous tuning of absorption, circular dichroism (CD), and fluorescence on a wide wavelength range. Band edge transitions were accompanied by circular dichroism peaks which red-shifted together with the increase in particle size. The clear correlation between absorption and CD bands as well as between absorption bands and size in semiconductor QDs was used to derive an experimental scaling law for optical activity. The decrease in the intensity of circular dichroism-to-absorption ratio (dissymmetry) with the increase in particle size was stronger than linear, probably exponential. In addition, strong material type dependence was observed. The CD line shape appeared to be sensitive to the nature of the transition and may thus serve as a tool for sorting out the electronic states of the QDs. Fluorescence-detected circular dichroism (FDCD) was introduced as a new probe of optically active fluorescent nanoparticles. The analysis of the size and material dependence of the chiroptical induction effect leads to the conclusion that it is primarily an electronic interaction effect between the adsorbed chiral molecules and the electron-hole states.
手性半胱氨酸修饰的 CdS 和 CdSe 量子点（QDs）的合成被调整以控制纳米颗粒的尺寸。这与尺寸分离一起，允许在宽波长范围内同时调谐吸收、圆二色性（CD）和荧光。边缘带跃迁伴随着圆二色性峰的红移，这与颗粒尺寸的增加有关。半导体 QDs 中吸收和 CD 带之间以及吸收带与尺寸之间的明显相关性被用于推导出光学活性的实验标度定律。随着颗粒尺寸的增加，圆二色性与吸收比（不对称性）的强度下降比线性更强，可能是指数级的。此外，还观察到强烈的材料类型依赖性。CD 线形状似乎对跃迁的性质敏感，因此可以作为一种工具来梳理 QDs 的电子态。荧光探测圆二色性（FDCD）被引入作为探测手性荧光纳米粒子的新探针。对手性诱导效应的尺寸和材料依赖性的分析得出结论，它主要是吸附手性分子和电子-空穴态之间的电子相互作用效应。
