Shape Evolution of CdSe Nanoparticles controlled by Halogen Compounds

TL;DR

This study demonstrates how halogen compounds influence the shape evolution of CdSe nanoparticles from nanorods to pyramids, revealing a new method for shape control through ligand chemistry.

Contribution

It introduces a novel approach to nanoparticle shape manipulation using halogenated additives supported by experimental and theoretical analysis.

Findings

Halogen compounds direct shape evolution of CdSe nanoparticles.

Ligand chemistry influences nanoparticle surface facets.

Chemical composition of ligand sphere changes during shape transformation.

Abstract

Halogen compounds are capable of playing an important role in the manipulation of nanoparticle shapes and properties. In a new approach, we examined the shape evolution of CdSe nanorods to hexagonal pyramids in a hot-injection synthesis under the influence of halogenated additives in the form of organic chlorine, bromine and iodine compounds. Supported by DFT calculations, this shape evolution is explained as a result of X-type ligand coordination to sloped and flat Cd-rich facets and an equilibrium shape strongly influenced by halides. Synchrotron XPS measurements and TXRF results show that the shape evolution is accompanied by a modification in the chemical composition of the ligand sphere. Our experimental results suggest that the molecular structure of the halogenated compound is related to the degree of the effect on both rod growth and further shape evolution. This presents a new degree of freedom in nanoparticle shape control and highlights the role of additives in nanoparticle synthesis and their possible in situ formation of ligands.