Electronic and vibrational structure of complexes of tetracyanoquinodimethane with cadmium chalcogenide quantum dots

Laura C. Cass, Nathaniel K. Swenson, Emily A Weiss

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

This paper describes the use of visible, near-infrared, and mid-infrared steady-state optical spectroscopy to study the geometries in which tetracyanoquinodimethane (TCNQ) adsorbs to the surfaces of highly cadmium enriched and near-stoichiometric CdSe quantum dots (QDs) in the formation of QD-TCNQ charge transfer (CT) complexes. Several TCNQ molecules are spontaneously reduced by chalcogenides on the surface of each CdSe QD. The degree of CT depends on the geometry with which the TCNQ adsorbs and the degree of distortion of TCNQ's geometry upon adsorption. Comparison of the electronic and vibrational spectra of CdSe QD-TCNQ complexes with those of CT complexes of TCNQ with molecular reductants (including molecular chalcogenides) and computer simulations of the geometries and vibrational spectra of the TCNQ-chalcogenide CT complexes show that (i) the Cd-enriched CdSe QDs reduce a factor of 7.4 more TCNQ molecules per QD than nearly stoichiometric CdSe QDs because surface selenides are more accessible in the Cd-enriched QDs than in the near-stoichiometric QDs and (ii) TCNQ interacts with surface selenides through several adsorption modes that result in different amounts of charge transfer and different degrees of geometric distortion of TCNQ. This study provides a framework for determining the range of adsorption geometries of small molecules on QD surfaces, and for optimizing QD surfaces to adsorb molecules in configurations with maximal electronic coupling between the QD and the adsorbate.

Original languageEnglish
Pages (from-to)18263-18270
Number of pages8
JournalJournal of Physical Chemistry C
Volume118
Issue number31
DOIs
Publication statusPublished - Aug 7 2014

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Cadmium
cadmium
Semiconductor quantum dots
quantum dots
electronic structure
Charge transfer
charge transfer
Geometry
geometry
Chalcogenides
Molecules
selenides
chalcogenides
Vibrational spectra
Adsorption
vibrational spectra
adsorption
tetracyanoquinodimethane
molecules
Infrared radiation

ASJC Scopus subject areas

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

Cite this

Electronic and vibrational structure of complexes of tetracyanoquinodimethane with cadmium chalcogenide quantum dots. / Cass, Laura C.; Swenson, Nathaniel K.; Weiss, Emily A.

In: Journal of Physical Chemistry C, Vol. 118, No. 31, 07.08.2014, p. 18263-18270.

Research output: Contribution to journalArticle

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