Atomistic simulations reveal ligand shell heterogeneity in perovskite quantum dots

The performance of colloidal quantum dots in optoelectronics, quantum technologies, and photocatalysis strongly depends on their organic ligand shells. However, understanding how these flexible molecules arrange themselves around nanocrystal surfaces remains challenging, particularly because conventional experimental techniques cannot easily resolve local variations.

In a recent Advanced Materials study, Feld and co-workers combined single-particle Förster resonance energy transfer (FRET) spectroscopy with atomistic molecular dynamics simulations using the Amsterdam Modeling Suite (AMS). By attaching fluorescent dyes to surface ligands, the researchers measured their distances from individual CsPbBr₃ perovskite quantum dots, revealing substantial variations even within the ligand shell of a single particle.

To understand the molecular origin of this heterogeneity, the authors used ADF 2024.102 with the GFN1-xTB tight-binding model to simulate dye-labeled ligands on CsPbBr₃ surfaces with different ligand compositions and surface coverages. Molecular dynamics simulations at 300 K, complemented by potential energy scans, provided insight into how the surrounding ligands influence the position and configuration of the fluorescent probe.

The simulations reproduced the experimentally observed range of dye-surface distances and showed that higher ligand coverage generally pushes the dye farther from the surface. Different ligand chemistries also influenced the preferred configurations. These findings suggest that variations in local ligand coverage contribute to the structural heterogeneity observed experimentally.

By connecting single-particle spectroscopy with atomistic modeling, the study demonstrates how AMS simulations can help interpret experimental measurements and reveal molecular-level details of complex nanomaterial interfaces. Such insights are valuable for understanding and ultimately controlling the surface chemistry of quantum dots used in light-emitting devices, quantum technologies, and photocatalysis.