On the pH-dependent quenching of quantum dot photoluminescence by redox active dopamine

Xin Ji, Goutam Palui, Tommaso Avellini, Hyon Bin Na, Chongyue Yi, Kenneth Knappenberger, Hedi Mattoussi

Research output: Contribution to journalArticle

145 Citations (Scopus)

Abstract

We investigated the charge transfer interactions between luminescent quantum dots (QDs) and redox active dopamine. For this, we used pH-insensitive ZnS-overcoated CdSe QDs rendered water-compatible using poly (ethylene glycol)-appended dihydrolipoic acid (DHLA-PEG), where a fraction of the ligands was amine-terminated to allow for controlled coupling of dopamine-isothiocyanate onto the nanocrystal. Using this sample configuration, we probed the effects of changing the density of dopamine and the buffer pH on the fluorescence properties of these conjugates. Using steady-state and time-resolved fluorescence, we measured a pronounced pH-dependent photoluminescence (PL) quenching for all QD-dopamine assemblies. Several parameters affect the PL loss. First, the quenching efficiency strongly depends on the number of dopamines per QD-conjugate. Second, the quenching efficiency is substantially increased in alkaline buffers. Third, this pH-dependent PL loss can be completely eliminated when oxygen-depleted buffers are used, indicating that oxygen plays a crucial role in the redox activity of dopamine. We attribute these findings to charge transfer interactions between QDs and mainly two forms of dopamine: the reduced catechol and oxidized quinone. As the pH of the dispersions is changed from acidic to basic, oxygen-catalyzed transformation progressively reduces the dopamine potential for oxidation and shifts the equilibrium toward increased concentration of quinones. Thus, in a conjugate, a QD can simultaneously interact with quinones (electron acceptors) and catechols (electron donors), producing pH-dependent PL quenching combined with shortening of the exciton lifetime. This also alters the recombination kinetics of the electron and hole of photoexcited QDs. Transient absorption measurements that probed intraband transitions supported those findings where a simultaneous pronounced change in the electron and hole relaxation rates was measured when the pH was changed from acidic to alkaline.

Original languageEnglish (US)
Pages (from-to)6006-6017
Number of pages12
JournalJournal of the American Chemical Society
Volume134
Issue number13
DOIs
StatePublished - Apr 4 2012

Fingerprint

Quantum Dots
Semiconductor quantum dots
Oxidation-Reduction
Quenching
Dopamine
Photoluminescence
Electrons
Quinones
Buffers
Oxygen
Polyethylene glycols
Charge transfer
8,11,14-Eicosatrienoic Acid
Fluorescence
Catechols
Ethylene Glycol
Dispersions
Excitons
Nanoparticles
Nanocrystals

All Science Journal Classification (ASJC) codes

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

Cite this

Ji, Xin ; Palui, Goutam ; Avellini, Tommaso ; Na, Hyon Bin ; Yi, Chongyue ; Knappenberger, Kenneth ; Mattoussi, Hedi. / On the pH-dependent quenching of quantum dot photoluminescence by redox active dopamine. In: Journal of the American Chemical Society. 2012 ; Vol. 134, No. 13. pp. 6006-6017.
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On the pH-dependent quenching of quantum dot photoluminescence by redox active dopamine. / Ji, Xin; Palui, Goutam; Avellini, Tommaso; Na, Hyon Bin; Yi, Chongyue; Knappenberger, Kenneth; Mattoussi, Hedi.

In: Journal of the American Chemical Society, Vol. 134, No. 13, 04.04.2012, p. 6006-6017.

Research output: Contribution to journalArticle

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AU - Palui, Goutam

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AU - Knappenberger, Kenneth

AU - Mattoussi, Hedi

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