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The Scaling of Ligand Concentration and Soret Effect Induced Phase Transition in CsPbBr3 Perovskite Quantum Dots
摘要： The intelligent chemistry strategy based automated machine is applied for the study of the phase transition in the CsPbBr3 quantum dots (QDs). With the in-situ photoluminescence (PL) signal detector and analysis module, the oleyl amine (OLA) and oleyl acid (OA) ligands concentration dependent diffusion picture are well derived, a three-stage power-law scaling is disclosed on the ligands concentration dependent growth, and a phase transformation from CsPbBr3 to Cs4PbBr6 QDs are confirmed. Based on the experimental analysis associated with the G0W0-BSE calculation, we confirmed that there is no significant PL signal in the pure Cs4PbBr6 structure. With the steady temperature control module, we find the ligand concentration and the Soret effect are isomorphic for the mass flux in the QDs nucleation and phase transformation. We find the activity of the surface states can be essential for the size dependence of the Soret effect in a general way.
关键词： CsPbBr3,Soret effect,quantum dots,phase transition,ligand concentration
更新于2025-09-16 10:30:52
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The Effect of Chiral Ligand Concentration and Binding Mode on Chiroptical Activity of CdSe/CdS Quantum Dots
摘要： Chiroptically active fluorescent semiconductor nanocrystals, quantum dots (QDs), are of high interest from a theoretical and technological point of view as they are promising candidates for a range of potential applications. Optical activity can be induced in QDs by capping them with chiral molecules, resulting in circular dichroism (CD) signals in the range of the QD UV-Vis absorption. However, the effects of the chiral ligand concentration and binding modes on the chiroptical properties of QDs are still poorly understood. In the present study, we report the strong influence of the concentration of a chiral aminoacid (cysteine) on its binding modes upon the CdSe/CdS QD’s surface, resulting in varying QD chiroptical activity and corresponding CD signals. Importantly, we demonstrate that the increase of cysteine concentration is accompanied by the growth of the QD CD intensity, reaching a certain critical point after which it starts to decrease. The intensity of the CD signal varies by almost an order of magnitude across this range. NMR and FTIR data, supported by DFT calculations, reveal a change in the binding mode of cysteine molecules from tridentate to bidentate when going from low to high concentrations, which results in a change in the CD intensity. Hence, we conclude that the chiroptical properties of QDs are dependent on the concentration and binding modes of the capping chiral ligands. These findings are very important for understanding chiroptical phenomena at the nanoscale and for the design of advanced optically active nanomaterials.
关键词： cysteine,chiroptical activity,density functional theory,quantum dots,chirality,ligand concentration,binding mode
更新于2025-09-12 10:27:22