Simultaneous determination of the adsorption constant and the photoinduced electron transfer rate for a Cds quantum dot - Viologen Complex

Adam J. Morris-Cohen, Matthew T. Frederick, Laura C. Cass, Emily A Weiss

Research output: Contribution to journalArticle

133 Citations (Scopus)

Abstract

Transient absorption (TA) spectroscopy of solution-phase mixtures of colloidal CdS quantum dots (QDs) with acid-derivatized viologen molecules, N-[1-heptyl],N′-[3-carboxypropyl]-4,4′-bipyridinium dihexafluorophosphate (V2+), indicates electron transfer occurs from the conduction band of the QD to the LUMO of V2+ after photoexcitation of a band-edge exciton in the QD. Analysis of the magnitude of the ground state bleach of the QD as a function of the molar ratio QD:V 2+ yields the QD - ligand adsorption constant, Ka (4.4 × 104 M-1) for V2+ ligands adsorbed in geometries conducive to electron transfer. The value of Ka, together with the measured rates of (i) formation of the V+• electron transfer product and (ii) recovery of the ground state bleach of the QD, enables determination of the intrinsic rate constant for charge separation, k CS,int ∼ 1.7 × 1010 s-1, the rate for a single QD - V2+ donor - acceptor pair. This analysis confirms previous reports that the number of ligands adsorbed to each QD is well-described by a Poisson distribution. This is the first report where the QD - ligand charge transfer and binding equilibria are quantitatively investigated simultaneously with a single technique.

Original languageEnglish
Pages (from-to)10146-10154
Number of pages9
JournalJournal of the American Chemical Society
Volume133
Issue number26
DOIs
Publication statusPublished - Jul 6 2011

Fingerprint

Viologens
Quantum Dots
Semiconductor quantum dots
Adsorption
Electrons
Ligands
Ground state
Poisson Distribution
Poisson distribution
Photoexcitation
Conduction bands
Absorption spectroscopy
Excitons
Charge transfer
Rate constants
Spectrum Analysis

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Simultaneous determination of the adsorption constant and the photoinduced electron transfer rate for a Cds quantum dot - Viologen Complex. / Morris-Cohen, Adam J.; Frederick, Matthew T.; Cass, Laura C.; Weiss, Emily A.

In: Journal of the American Chemical Society, Vol. 133, No. 26, 06.07.2011, p. 10146-10154.

Research output: Contribution to journalArticle

@article{ea45ee866e234b8f8729bc14ef458891,
title = "Simultaneous determination of the adsorption constant and the photoinduced electron transfer rate for a Cds quantum dot - Viologen Complex",
abstract = "Transient absorption (TA) spectroscopy of solution-phase mixtures of colloidal CdS quantum dots (QDs) with acid-derivatized viologen molecules, N-[1-heptyl],N′-[3-carboxypropyl]-4,4′-bipyridinium dihexafluorophosphate (V2+), indicates electron transfer occurs from the conduction band of the QD to the LUMO of V2+ after photoexcitation of a band-edge exciton in the QD. Analysis of the magnitude of the ground state bleach of the QD as a function of the molar ratio QD:V 2+ yields the QD - ligand adsorption constant, Ka (4.4 × 104 M-1) for V2+ ligands adsorbed in geometries conducive to electron transfer. The value of Ka, together with the measured rates of (i) formation of the V+• electron transfer product and (ii) recovery of the ground state bleach of the QD, enables determination of the intrinsic rate constant for charge separation, k CS,int ∼ 1.7 × 1010 s-1, the rate for a single QD - V2+ donor - acceptor pair. This analysis confirms previous reports that the number of ligands adsorbed to each QD is well-described by a Poisson distribution. This is the first report where the QD - ligand charge transfer and binding equilibria are quantitatively investigated simultaneously with a single technique.",
author = "Morris-Cohen, {Adam J.} and Frederick, {Matthew T.} and Cass, {Laura C.} and Weiss, {Emily A}",
year = "2011",
month = "7",
day = "6",
doi = "10.1021/ja2010237",
language = "English",
volume = "133",
pages = "10146--10154",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "26",

}

TY - JOUR

T1 - Simultaneous determination of the adsorption constant and the photoinduced electron transfer rate for a Cds quantum dot - Viologen Complex

AU - Morris-Cohen, Adam J.

AU - Frederick, Matthew T.

AU - Cass, Laura C.

AU - Weiss, Emily A

PY - 2011/7/6

Y1 - 2011/7/6

N2 - Transient absorption (TA) spectroscopy of solution-phase mixtures of colloidal CdS quantum dots (QDs) with acid-derivatized viologen molecules, N-[1-heptyl],N′-[3-carboxypropyl]-4,4′-bipyridinium dihexafluorophosphate (V2+), indicates electron transfer occurs from the conduction band of the QD to the LUMO of V2+ after photoexcitation of a band-edge exciton in the QD. Analysis of the magnitude of the ground state bleach of the QD as a function of the molar ratio QD:V 2+ yields the QD - ligand adsorption constant, Ka (4.4 × 104 M-1) for V2+ ligands adsorbed in geometries conducive to electron transfer. The value of Ka, together with the measured rates of (i) formation of the V+• electron transfer product and (ii) recovery of the ground state bleach of the QD, enables determination of the intrinsic rate constant for charge separation, k CS,int ∼ 1.7 × 1010 s-1, the rate for a single QD - V2+ donor - acceptor pair. This analysis confirms previous reports that the number of ligands adsorbed to each QD is well-described by a Poisson distribution. This is the first report where the QD - ligand charge transfer and binding equilibria are quantitatively investigated simultaneously with a single technique.

AB - Transient absorption (TA) spectroscopy of solution-phase mixtures of colloidal CdS quantum dots (QDs) with acid-derivatized viologen molecules, N-[1-heptyl],N′-[3-carboxypropyl]-4,4′-bipyridinium dihexafluorophosphate (V2+), indicates electron transfer occurs from the conduction band of the QD to the LUMO of V2+ after photoexcitation of a band-edge exciton in the QD. Analysis of the magnitude of the ground state bleach of the QD as a function of the molar ratio QD:V 2+ yields the QD - ligand adsorption constant, Ka (4.4 × 104 M-1) for V2+ ligands adsorbed in geometries conducive to electron transfer. The value of Ka, together with the measured rates of (i) formation of the V+• electron transfer product and (ii) recovery of the ground state bleach of the QD, enables determination of the intrinsic rate constant for charge separation, k CS,int ∼ 1.7 × 1010 s-1, the rate for a single QD - V2+ donor - acceptor pair. This analysis confirms previous reports that the number of ligands adsorbed to each QD is well-described by a Poisson distribution. This is the first report where the QD - ligand charge transfer and binding equilibria are quantitatively investigated simultaneously with a single technique.

UR - http://www.scopus.com/inward/record.url?scp=79959914257&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79959914257&partnerID=8YFLogxK

U2 - 10.1021/ja2010237

DO - 10.1021/ja2010237

M3 - Article

C2 - 21618976

AN - SCOPUS:79959914257

VL - 133

SP - 10146

EP - 10154

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 26

ER -