X-ray total scattering study of regular and magic-size nanoclusters of cadmium sulphide

TL;DR

This study uses x-ray total scattering to analyze the atomic structures of regular and magic-size cadmium sulphide nanoclusters, revealing differences in short-range and long-range order and ligand effects.

Contribution

It provides detailed atomic-level insights into the structure of magic-size CdS nanoclusters, distinguishing them from regular quantum dots and highlighting ligand influences.

Findings

Regular quantum dots show mixed phase structures due to stacking disorder.

Magic-size clusters have bulk-like short-range order but different long-range structures from bulk and regular dots.

Ligand type can significantly influence the atomic structure of magic-size nanoclusters.

Abstract

Four kinds of magic-size CdS clusters and two different regular CdS quantum dots have been studied by x-ray total scattering technique and pair distribution function method. Results for the regular CdS quantum dots could be modelled as a mixed phase of atomic structures based on the two bulk crystalline phases, which is interpreted as representing the effects of stacking disorder. However, the results for the magic-size clusters were significantly different. On one hand, the short-range features in the pair distribution function reflect the bulk, indicating that these structures are based on the same tetrahedral coordination found in the bulk phases (and therefore excluding new types of structures such as cage-like arrangements of atoms). But on the other hand, the longer- range atomic structure clearly does not reflect the layer structures found in the bulk and the regular quantum dots. We compare the effects of two ligands, phenylacetic acid and oleic acid, showing that in two cases the ligand has little effect on the atomic structure of the magic-size nanocluster and in another it has a significant effect.