Precision synthesis and atomistic analysis of deep blue cubic quantum dots made via self-organization

Abstract

As a crystal approaches a few nm in size, atoms become nonequivalent, bonds vibrate, and quantum effects emerge. To study quantum dots (QDs) with structural control common in molecular science, we need atomic precision synthesis and analysis. We describe here the synthesis of QDs of lead bromide perovskite via self-organization of a lead malate chelate complex and PbBr3– under ambient conditions. Millisecond and angstrom resolution electron microscopic analysis revealed the structure and the dynamic behavior of individual QDs—structurally uniform cubes made of 64 lead atoms, where eight malate molecules are located on the eight corners of the cubes, and oleylamonium cations lipophilize and stabilize the edges and faces. Lacking translational symmetry, the cube is to be viewed as a molecule rather than a nanocrystal. The QD exhibits quantitative photoluminescence and stable electroluminescence at 460 nm with a narrow half-maximum linewidth of 15 nm, reflecting minimum structural defects. This controlled synthesis and precise analysis demonstrate the potential of cinematic chemistry for the characterization of nanomaterials beyond the conventional limit.

Precision Synthesis and Atomistic Analysis of Deep-Blue Cubic Quantum Dots Made via Self-Organization

“…By adding malic acid (MLA), we could prevent the formation of irregular structures and instead formed micron-sized cubes, whose size could be decreased by the addition of oleylamine, leading to the exclusive formation of ≈2.5 nm blue-emitting perovskite nanoclusters. 31 Theory predicts blue emission of a lead bromide perovskite QD such as Cs 112 Pb 64 Br 240 (Cs•QD 4 , Figure 1c, see Supplementary Note 1). 31 However, in practice, previous studies showed that it is unstable and has poor metrics because of dangling bonds and surface defects 33 and the dynamic nature of the QD−ligand interaction.…”

“…31 Theory predicts blue emission of a lead bromide perovskite QD such as Cs 112 Pb 64 Br 240 (Cs•QD 4 , Figure 1c, see Supplementary Note 1). 31 However, in practice, previous studies showed that it is unstable and has poor metrics because of dangling bonds and surface defects 33 and the dynamic nature of the QD−ligand interaction. 34 We report here the synthesis of QDs methylammonium ion, MA + ) at room temperature in air via selforganization of a lead malate chelate complex 35 and PbBr 3 − via a corner−edge−corner intermediate similar to the one we previously described for the formation of bulk crystals (Figure 1d).…”

“…We demonstrate that in a ligand-less synthesis, perovskite precursors quickly grow to form elongated dodecahedra and cuboids (Figure b). By adding malic acid (MLA), we could prevent the formation of irregular structures and instead formed micron-sized cubes, whose size could be decreased by the addition of oleylamine, leading to the exclusive formation of ≈2.5 nm blue-emitting perovskite nanoclusters …”