Cation Exchange and Spontaneous Crystal Repair Resulting in Ultrathin, Planar CdS Nanosheets

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Abstract

Cation exchange has become a major postsynthetic tool to obtain nanocrystals with a combination of stoichiometry, size, and shape that is challenging to achieve by direct wet-chemical synthesis. Here, we report on the transformation of highly anisotropic, ultrathin, and planar PbS nanosheets into CdS nanosheets of the same dimensions. We monitor the evolution of the Cd-for-Pb exchange by ex-situ TEM, HAADF-STEM, and EDX. We observe that in the early stages of the exchange the sheets show large in-sheet voids that repair spontaneously upon further exchange and annealing, resulting in ultrathin, planar, and crystalline CdS nanosheets. After cation exchange, the nanosheets show broad sub-band gap luminescence, as often observed in CdS nanocrystals. The photoluminescence excitation spectrum reveals the heavy- and light-hole exciton features, with very strong quantum confinement and large electron–hole Coulomb energy, typical for 2D ultrathin Cd-chalcogenide nanosheets.
Original languageEnglish
Pages (from-to)8301-8308
Number of pages8
JournalChemistry of Materials
Volume35
Issue number19
DOIs
Publication statusPublished - 10 Oct 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.

Funding

M.M.S. and D.V. acknowledge financial support from the European ERC Council, ERC Advanced grant 692691 “First Step”. D.V. acknowledges the research program “Materials for the Quantum Age” (QuMat) for financial support, which is part of the Gravitation program financed by the Dutch Ministry of Education, Culture and Science (OCW, registration number 024.005.006).

FundersFunder number
European ERC Council
European Research Council692691
Ministerie van onderwijs, cultuur en wetenschap024.005.006

    Keywords

    • Ligand-exchange
    • Nanocrystals
    • Nanoplatelets
    • Quantum dots

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