The effect of molecular isomerism on the induced circular dichroism of cadmium sulfide quantum dots
The effect of molecular isomerism on the induced circular dichroism of cadmium sulfide quantum dots
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分子异构现象对硫化镉量子点诱导圆二色性的影响
DOI：
10.1039/d1tc04496f
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发表时间：
2021
影响因子：
6.4
通讯作者：
Balaz, Milan
中科院分区：
文献类型：
--
作者：
Joh, Yoonbin A.;Kwon, Yuri H.;Tannir, Shambhavi;Leonard, Brian M.;Kubelka, Jan;Varga, Krisztina;Balaz, Milan
合成后相转移配体交换已被建立为一种简单、可靠和通用的方法，用于合成显示圆二色性（CD）和圆偏振发光（CPL）的手性、光学活性胶体纳米晶体。在此，我们提出了一个无水和纯化的环己烷→甲醇配体交换系统，导致稳定的，非聚集的手性和荧光硫化镉量子点（CdS量子点）的合成。吸收和发射的研究表明，羧酸封端配体可以调整的带隙高达65毫电子伏，以及控制的带隙和深陷阱发射途径。CD数据表明，第二个立体中心的加入并没有自动导致量子点的CD各向异性的增加，而是匹配/错配协同效应必须考虑在手性从封端配体转移到非手性纳米晶体。官能团的位置变化以及官能团的化学身份影响诱导CD光谱的形状和各向异性，并揭示了官能团的配位和极性对结合几何形状和诱导手性性质的重要性。最后，我们描述了第一个例子，其中CD光谱的量子点与相同的配体和溶解在相同的溶剂中显示非常不同的光谱曲线。这一工作为量子点诱导CD的研究提供了更深入的认识，为合理设计手性纳米材料铺平了道路。
Post-synthetic phase transfer ligand exchange has been established as a simple, reliable, and versatile method for the synthesis of chiral, optically active colloidal nanocrystals displaying circular dichroism (CD) and circularly polarized luminescence (CPL). Herein we present a water-free and purification-free cyclohexane → methanol ligand exchange system that led to the synthesis of stable, non-aggregating chiral and fluorescent cadmium sulfide quantum dots (CdS QDs). Absorption and emission studies revealed that the carboxylate capping ligands can tune the band gap by up to 65 meV as well as control the band gap and deep trap emission pathways. The CD data revealed that the addition of a 2nd stereogenic center did not automatically lead to an increase of the CD anisotropy of QDs, but rather match/mismatch cooperativity effects must be considered in the transfer of the chirality from the capping ligands to the achiral nanocrystals. Variation in position of the functional groups as well as the chemical identity of the functional groups impacted both the shape and anisotropy of the induced CD spectra and revealed the importance of the functional groups’ coordination and polarity on the binding geometry and induced chiroptical properties. Finally, we describe the first example where CD spectra of QDs capped with the same ligand and dissolved in the same solvent displayed very different spectral profiles. This work provides deeper insight into induced CD of QDs and paves the path to rational design of chiral nanomaterials.