Visualizing heterogeneity of monodisperse CdSe nanocrystals by their assembly into three-dimensional supercrystals

Elena V. Shevchenko, Paul Podsiadlo, Xiaohua Wu, Byeongdu Lee, Tijana Rajh, Rachel Morin, Matthew Pelton

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We show that the self-assembly of monodisperse CdSe nanocrystals synthesized at lower temperature (∼310 °C) into three-dimensional supercrystals results in the formation of separate regions within the supercrystals that display photoluminescence at two distinctly different wavelengths. Specifically, the central portions of the supercrystals display photoluminescence and absorption in the orange region of the spectrum, around 585 nm, compared to the 575 nm photoluminescence maximum for the nanocrystals dispersed in toluene. Distinct domains on the surfaces and edges of the supercrystals, by contrast, display photoluminescence and absorption in the green region of the spectrum, around 570 nm. We attribute the different-colored domains to two subpopulations of NCs in the monodisperse ensemble: the nanocrystals in the “orange” regions are chemically stable, whereas the nanocrystals in the “green” regions are partially oxidized. The susceptibility of the “green” nanocrystals to oxidation indicates a lower coverage of capping molecules on these nanocrystals. We propose that the two subpopulations correspond to nanocrystals with different surfaces that we attribute to the polytypism of CdSe.

Original languageEnglish (US)
Pages (from-to)14989-14998
Number of pages10
JournalACS nano
Volume14
Issue number11
DOIs
StatePublished - Nov 24 2020
Externally publishedYes

Keywords

  • Nanocrystals
  • Photoluminescence
  • Polymorphism
  • Polytypism
  • Self-assembly
  • Superlattices

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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