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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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Publication details

The article was received on 26 Feb 2019, accepted on 14 May 2019 and first published on 05 Jun 2019


Article type: Edge Article
DOI: 10.1039/C9SC00989B
Chem. Sci., 2019,10, 6539-6552
  • Open access: Creative Commons BY license
    All publication charges for this article have been paid for by the Royal Society of Chemistry

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    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.

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