Optically Active CdSe/CdS Nanoplatelets Exhibiting Both Circular Dichroism and Circularly Polarized Luminescence
Ligand-induced chirality in colloidal semiconductor nanocrystals attracts attention because of their tunable chiroptical properties. Here, the induced chirality and circularly polarized luminescence (CPL) are investigated as a function of the CdS shell growth in a range of 2D CdSe/CdS nanoplatelets (NPLs) capped with chiral ligands. Five samples of CdSe/CdS NPLs are synthesized by a one-pot approach to vary the island-like shell on a four-monolayer (4 ML) CdSe NPLs core, which effectively reduces the interfacial strain energy. The successful preparation of L-/D-Cysteine-capped CdSe/CdS NPLs with both tunable circular dichroism (CD) and CPL behaviors and a maximum anisotropic luminance factor ( g lum ) of 5.29 × 10 −4 is described. The induced chiroptical response shows a direct relationship with the formation of island-like shell in the first and second stages and shows a clear signal evolution. In the third stage with a full coating shell, the CD and CPL signals are inversely proportional to the CdS shell thickness. The island-like shell gives birth to the CPL signal, while the formation of full coating shell decreases the induced chirality. Such chiral and emissive NPLs provide an ideal platform for the rational design of semiconductor nanocrystals with chiroptical properties in areas of biomedicine, polarizers, and new generation of display devices.
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