Role of solvent-oxygen ion pairs in photooxidation of CdSe nanocrystal quantum dots

Virginia W. Manner, Alexey Y. Koposov, Paul Szymanski, Victor I Klimov, Milan Sykora

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Understanding the mechanisms for photodegradation of nanocrystal quantum dots is an important step toward their application in real-world technologies. A usual assumption is that photochemical modifications in nanocrystals, such as their photooxidation, are triggered by absorption of a photon in the dot itself. Here, we demonstrate that, contrary to this commonly accepted picture, nanocrystal oxidation can be initiated by photoexcitation of solvent-oxygen ion pairs that relax to produce singlet oxygen, which then reacts with the nanocrystals. We make this conclusion on the basis of photolysis studies of solutions of CdSe nanocrystals. Our measurements indicate a sharp spectral onset for photooxidation, which depends on solvent identity and is 4.8 eV for hexane and 3.4 eV for toluene. Importantly, the photooxidation onset correlates with the position of a new optical absorption feature, which develops in a neat solvent upon its exposure to oxygen. This provides direct evidence that nanocrystal photooxidation is mediated by excitation of solvent-oxygen pairs and suggests that the stability of the nanocrystals is defined by not only the properties of their surfaces (as has been commonly believed) but also the properties of their environment, that is, of the surrounding solvent or matrix.

Original languageEnglish
Pages (from-to)2371-2377
Number of pages7
JournalACS Nano
Volume6
Issue number3
DOIs
Publication statusPublished - Mar 27 2012

Fingerprint

Photooxidation
photooxidation
oxygen ions
Nanocrystals
Semiconductor quantum dots
nanocrystals
quantum dots
Ions
Oxygen
oxygen
Singlet Oxygen
Photoexcitation
Photodegradation
Photolysis
Toluene
Hexanes
Hexane
photoexcitation
Light absorption
photolysis

Keywords

  • degradation
  • nanocrystals
  • oxidation
  • photochemistry
  • photooxidation
  • quantum dots

ASJC Scopus subject areas

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

Cite this

Role of solvent-oxygen ion pairs in photooxidation of CdSe nanocrystal quantum dots. / Manner, Virginia W.; Koposov, Alexey Y.; Szymanski, Paul; Klimov, Victor I; Sykora, Milan.

In: ACS Nano, Vol. 6, No. 3, 27.03.2012, p. 2371-2377.

Research output: Contribution to journalArticle

Manner, VW, Koposov, AY, Szymanski, P, Klimov, VI & Sykora, M 2012, 'Role of solvent-oxygen ion pairs in photooxidation of CdSe nanocrystal quantum dots', ACS Nano, vol. 6, no. 3, pp. 2371-2377. https://doi.org/10.1021/nn2046289
Manner, Virginia W. ; Koposov, Alexey Y. ; Szymanski, Paul ; Klimov, Victor I ; Sykora, Milan. / Role of solvent-oxygen ion pairs in photooxidation of CdSe nanocrystal quantum dots. In: ACS Nano. 2012 ; Vol. 6, No. 3. pp. 2371-2377.
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