Decoding structural transitions from CdSe nanoclusters to quantum dots through dynamic nuclear polarization NMR.

Achieving control over quantum dot size is essential for their performance, but remains challenging due to the limited atomic-level understanding of quantum dot growth. In this study, we employ signal-enhancing Dynamic Nuclear Polarization solid-state NMR to investigate the structural features of intermediate CdSe clusters and mature quantum dots to gain valuable insights. By integrating quantum mechanical calculations with experimental data, we leverage 113Cd chemical shift to elucidate local Cd environments at various positions, decoding the complex ligand distribution on cluster surfaces. Our findings reveal that ligand distribution is stabilizing through inter-ligand hydrogen bonds, while minimizing steric clashes during ligand packing on space-constrained planar facets. This study underscores the unique capability of 113Cd NMR to probe local Cd environments, offering a framework for monitoring structural transitions and improving size control during quantum dot growth.