Chabeda Daniel, Gee Stephen, Rabani Eran
Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
Department of Materials, University of California, Santa Barbara, Santa Barbara, California 93106-5050, United States.
J Phys Chem Lett. 2024 Aug 8;15(31):7863-7869. doi: 10.1021/acs.jpclett.4c01682. Epub 2024 Jul 25.
Recent experiments have probed the chiral properties of semiconductor nanocrystal (NC) quantum dots (QDs), but understanding the circular dichroism line shape, excitonic features, and chirality induction mechanism remains a challenge. We propose an atomistic pseudopotential method to model chiral ligand passivated QDs, computing circular dichroism (CD) spectra for CdSe QDs (2.6-3.8 nm). We find strong agreement between calculated and measured line shapes, predicting consistent bisignate line shapes with decreasing CD magnitude as size increases. Our analysis reveals the origin of bisignate line shapes, arising from nondegenerate excitons with opposing angular momenta. We also explore the impact of chiral ligand orientation on QD surfaces, observing changes in the optical activity magnitude and sign. This orientation sensitivity offers the means to distinguish ordered from disordered ligand configurations, facilitating the study of order-disorder transitions at ligand-QD interfaces.
最近的实验探究了半导体纳米晶体（NC）量子点（QD）的手性特性，但理解圆二色性线形、激子特征和手性诱导机制仍然是一项挑战。我们提出一种原子赝势方法来模拟手性配体钝化的量子点，计算CdSe量子点（2.6 - 3.8纳米）的圆二色性（CD）光谱。我们发现计算出的和测量得到的线形之间有很强的一致性，预测随着尺寸增加，CD幅度减小，双线形保持一致。我们的分析揭示了双线形的起源，它源于具有相反角动量的非简并激子。我们还探讨了手性配体在量子点表面的取向影响，观察到光学活性大小和符号的变化。这种取向敏感性提供了区分有序和无序配体构型的方法，有助于研究配体 - 量子点界面处的有序 - 无序转变。
