Colloidal Synthesis of CsX Nanocrystals (X = Cl, Br, I).

Peter Shaw,Sara Martí-Sánchez,Pavlos Lagoudakis,Albert Grau-Carbonell,Yong Zuo,Jordi Arbiol,Michaela Meyns,Martin Charlton,Andreu Cabot,Antonios Kanaras

doi:10.3390/nano8070506

Abstract

A facile colloidal synthesis of highly ionic cesium halide nanocrystals is reported. Colloidal nanocrystals of CsI, CsCl and CsBr with unprecedentedly small dimensions are obtained using oleylammonium halides and cesium oleate as precursors. The ease and adaptability of our method enables its universalization for the formation of other highly ionic nanocrystals.

Highlights

The colloidal synthesis of nanocrystals has reached a degree of control over composition, size and shape that allows precise manipulation of physical and chemical properties of a wide range of materials
To obtain cesium halide nanocrystals, we injected a hot solution of cesium oleate into a solution of the desired halide precursor and oleic acid in octadecene [22,23]
For optimum solubility and to avoid the use of further metal cations, we employed oleylammonium halides, prepared from oleylamine and the respective mineral acid [21], as a combined source of anions and a stabilizer. The temperature of both solutions was kept at 120 ◦C and the reaction was left to proceed for 5 s before cooling down in an ice–water bath

Summary

Introduction

The colloidal synthesis of nanocrystals has reached a degree of control over composition, size and shape that allows precise manipulation of physical and chemical properties of a wide range of materials. Despite this fact, highly ionic compounds, such as alkali halides, are a class of materials that form macroscopic crystals of high purity and quality, but pose a significant challenge in regard to nanocrystal formation. The most ionic examples of alkali halides and, the most ionic binary compounds available are the halides of cesium, CsX (X = F, Cl, Br, I) These materials exhibit wide band-gaps, with energies ranging from 6.1 to 8.3 eV at ambient conditions [1,2,3], while changing to metallic phase at high pressures [4]. A peculiarity of CsI and CsCl is their ability to exhibit an optical color due to the phenomenon of halide vacancies, an effect that is still being actively investigated in other alkali halide salts [1,3,5]

Methods

Results

Conclusion