Precursor reaction kinetics control compositional grading and size of CdSe 1- x S x nanocrystal heterostructures.

Autor: Hamachi LS; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu., Yang H; The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA., Jen-La Plante I; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu., Saenz N; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu., Qian K; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu., Campos MP; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu., Cleveland GT; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu., Rreza I; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu., Oza A; Department of Chemistry , Barnard College , New York , New York 10027 , USA . Email: acrowthe@barnard.edu., Walravens W; Physics and Chemistry of Nanostructures Group (PCN) , Ghent University , B-9000 Ghent , Belgium., Chan EM; The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA., Hens Z; Physics and Chemistry of Nanostructures Group (PCN) , Ghent University , B-9000 Ghent , Belgium.; Center of Nano and Biophotonics , Ghent University , B-9000 Ghent , Belgium., Crowther AC; Department of Chemistry , Barnard College , New York , New York 10027 , USA . Email: acrowthe@barnard.edu., Owen JS; Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email: jso2115@columbia.edu.
Jazyk: angličtina
Zdroj: Chemical science [Chem Sci] 2019 Jun 05; Vol. 10 (26), pp. 6539-6552. Date of Electronic Publication: 2019 Jun 05 (Print Publication: 2019).
DOI: 10.1039/c9sc00989b
Abstrakt: We report a method to control the composition and microstructure of CdSe 1- x S x 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 ( k E ) spanning 1.3 × 10 -5 s -1 to 2.0 × 10 -1 s -1 . Depending on the relative reactivity ( k Se / k S ), 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. CdSe 1- x S x alloys ( k Se / k S = 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.
Databáze: MEDLINE
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