Issue 26, 2019

Precursor reaction kinetics control compositional grading and size of CdSe1−xSx nanocrystal heterostructures

Abstract

We report a method to control the composition and microstructure of CdSe1−xSx nanocrystals by the simultaneous injection of sulfide and selenide precursors into a solution of cadmium oleate and oleic acid at 240 °C. Pairs of substituted thio- and selenoureas were selected from a library of compounds with conversion reaction reactivity exponents (kE) spanning 1.3 × 10−5 s−1 to 2.0 × 10−1 s−1. Depending on the relative reactivity (kSe/kS), core/shell and alloyed architectures were obtained. Growth of a thick outer CdS shell using a syringe pump method provides gram quantities of brightly photoluminescent quantum dots (PLQY = 67 to 90%) in a single reaction vessel. Kinetics simulations predict that relative precursor reactivity ratios of less than 10 result in alloyed compositions, while larger reactivity differences lead to abrupt interfaces. CdSe1−xSx alloys (kSe/kS = 2.4) display two longitudinal optical phonon modes with composition dependent frequencies characteristic of the alloy microstructure. When one precursor is more reactive than the other, its conversion reactivity and mole fraction control the number of nuclei, the final nanocrystal size at full conversion, and the elemental composition. The utility of controlled reactivity for adjusting alloy microstructure is discussed.

Graphical abstract: Precursor reaction kinetics control compositional grading and size of CdSe1−xSx nanocrystal heterostructures

Supplementary files

Article information

Article type
Edge Article
Submitted
26 Feb 2019
Accepted
14 May 2019
First published
05 Jun 2019
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2019,10, 6539-6552

Precursor reaction kinetics control compositional grading and size of CdSe1−xSx nanocrystal heterostructures

L. S. Hamachi, H. Yang, I. Jen-La Plante, N. Saenz, K. Qian, M. P. Campos, G. T. Cleveland, I. Rreza, A. Oza, W. Walravens, E. M. Chan, Z. Hens, A. C. Crowther and J. S. Owen, Chem. Sci., 2019, 10, 6539 DOI: 10.1039/C9SC00989B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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