Fluorescence and Optical Activity of Chiral CdTe Quantum Dots in Their Interaction with Amino Acids
Fluorescence and Optical Activity of Chiral CdTe Quantum Dots in Their Interaction with Amino Acids
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手性 CdTe 量子点与氨基酸相互作用的荧光和光学活性
DOI：
10.1021/acsnano.9b09101
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发表时间：
2020-04-28
期刊：
影响因子：
17.1
通讯作者：
Yang, Gaoling
中科院分区：
文献类型：
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作者：
Li, Guangmin;Fei, Xuening;Yang, Gaoling
半导体纳米晶体中的配体诱导手性在过去几年中得到了广泛的研究，并在光学和生物学方面显示出潜在的应用。然而，半导体纳米粒子中手旋光效应的起源仍然没有完全理解。在这里，我们研究了与氨基酸的相互作用对手性半导体量子点（QD）的荧光和光学活性的影响。当与所有测试的氨基酸相互作用时，观察到1/d-Cys-CdTe QD的显著荧光增强，表明非辐射途径的抑制以及通过氨基与CdTe QD表面的相互作用而带来的表面陷阱位点的钝化。异手性氨基酸被证明会削弱圆二色性（CD）信号，这可能是由于半胱氨酸分子在量子点表面上的不同结合构型。此外，仅在添加半胱氨酸后观察到1/d-Cys-CdTe QD中的CD和荧光信号的红移，而其他测试的氨基酸不表现出这种效果。我们推测巯基诱导半胱氨酸的最高占据分子轨道（HOMO）和CdTe量子点的价带的轨道杂化，导致的能量带隙的减少和伴随的CD和荧光光谱的红移。密度泛函理论计算进一步验证了这一点。实验和理论研究结果都表明，添加不与QD的价带（VB）“直接”相互作用的配体（noncysteine moieties）改变了QD的物理性质，因为它可能改变了半胱氨酸与表面结合的方式。因此，我们得出结论，它不仅是化学的氨基酸配体，影响CD和PL，但也修改这些属性的确切几何结合。因此，了解QD的表面和手性氨基酸之间的关系提供了一个额外的视角，在半导体纳米粒子中诱导手性效应的根本起源，可能使我们能够优化手性半导体QD的手性应用的设计。
Ligand-induced chirality in semiconducting nanocrystals has been the subject of extensive study in the past few years and shows potential applications in optics and biology. Yet, the origin of the chiroptical effect in semiconductor nanoparticles is still not fully understood. Here, we examine the effect of the interaction with amino acids on both the fluorescence and the optical activity of chiral semiconductor quantum dots (QDs). A significant fluorescence enhancement is observed for l/d-Cys-CdTe QDs upon interaction with all the tested amino acids, indicating suppression of nonradiative pathways as well as the passivation of surface trap sites brought via the interaction of the amino group with the CdTe QDs’ surface. Heterochiral amino acids are shown to weaken the circular dichroism (CD) signal, which may be attributed to a different binding configuration of cysteine molecules on the QDs’ surface. Furthermore, a red shift of both CD and fluorescence signals in l/d-Cys-CdTe QDs is only observed upon adding cysteine, while other tested amino acids do not exhibit such an effect. We speculate that the thiol group induces orbital hybridization of the highest occupied molecular orbital (HOMOs) of cysteine and the valence band of CdTe QDs, leading to the decrease of the energy band gap and a concomitant red shift of CD and fluorescence spectra. This is further verified by density functional theory calculations. Both the experimental and theoretical findings indicate that the addition of ligands that do not “directly” interact with the valence band (VB) of the QD (noncysteine moieties) changes the QD photophysical properties, as it probably modifies the way cysteine is bound to the surface. Hence, we conclude that it is not only the chemistry of the amino acid ligand that affects both CD and PL but also the exact geometry of binding that modifies these properties. Understanding the relationship between the QD’s surface and chiral amino acid thus provides an additional perspective on the fundamental origin of induced chiroptical effects in semiconductor nanoparticles, potentially enabling us to optimize the design of chiral semiconductor QDs for chiroptic applications.