Measurement of wavelength-dependent polarization character in the absorption anisotropies of ensembles of CdSe nanorods

Daniel B. Tice, David J. Weinberg, Nathan Mathew, Robert P. H. Chang, Emily A Weiss

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Transient absorption (TA) and photoluminescence excitation (PLE) anisotropy measurements were used to investigate the polarization of band-edge and above-band-edge excitonic states in ensembles of CdSe nanocrystals with aspect ratios of 1:1, 3:1, and 10:1, dispersed in hexanes. The 1:1 nanocrystals (quantum dots) are isotropic absorbers and emitters. The 10:1 nanorods have a nonzero but featureless anisotropy spectrum above the band edge due to heterogeneity in the crystal structure and, therefore, electronic structure within single nanorods. The nanocrystals with an aspect ratio of 3:1, which are largely single crystals, have PLE and TA anisotropy spectra with features that correspond to those in the absorption spectrum. Direct measurement of the TA anisotropy spectrum of the nanorods and comparison with the PLE anisotropy spectrum reveal that the band-edge absorptive and emissive transitions contain both linear (z) and planar (xy) character. The degree of planar character at the band-edge states, modulated by classical local field effects arising from the dielectric contrast between the nanorod and the solvent, limits the degree of photoselection at this wavelength. The variation in the magnitude of the xy projection of the absorptive transitions within states above the band edge is responsible for the wavelength dependence of the absorption and emission anisotropies.

Original languageEnglish
Pages (from-to)13289-13296
Number of pages8
JournalJournal of Physical Chemistry C
Volume117
Issue number25
DOIs
Publication statusPublished - Jun 27 2013

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Nanorods
nanorods
Anisotropy
Polarization
Wavelength
anisotropy
polarization
wavelengths
Nanocrystals
Photoluminescence
nanocrystals
photoluminescence
aspect ratio
Aspect ratio
excitation
Hexanes
Hexane
Semiconductor quantum dots
Electronic structure
Absorption spectra

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Measurement of wavelength-dependent polarization character in the absorption anisotropies of ensembles of CdSe nanorods. / Tice, Daniel B.; Weinberg, David J.; Mathew, Nathan; Chang, Robert P. H.; Weiss, Emily A.

In: Journal of Physical Chemistry C, Vol. 117, No. 25, 27.06.2013, p. 13289-13296.

Research output: Contribution to journalArticle

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