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Issue 26, 2019
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Precursor reaction kinetics control compositional grading and size of CdSe1−xSx nanocrystal heterostructures

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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

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Supplementary files

Article information


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

Chem. Sci., 2019,10, 6539-6552
Article type
Edge Article

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

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    [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC.
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    [Original citation] - Published by The Royal Society of Chemistry.

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