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Proceedings Paper

Understanding the redox coupling between quantum dots and the neurotransmitter dopamine in hybrid self-assemblies
Author(s): Xin Ji; Nikolay S. Makarov; Wentao Wang; Goutam Palui; Istvan Robel; Hedi Mattoussi
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Paper Abstract

Interactions between luminescent fluorophores and redox active molecules often involve complex charge transfer processes, and have great ramifications in biology. Dopamine is a redox active neurotransmitter involved in a range of brain activities. We used steady-state and time-resolved fluorescence along with transient absorption bleach measurements, to probe the effects of changing the QD size and valence on the rate of photoluminescence quenching in QD-dopamine conjugates, when the pH of the medium was varied. In particular, we measured substantially larger quenching efficiencies, combined with more pronounced shortening in the PL lifetime decay when smaller size QDs and/or alkaline pH were used. Moreover, we found that changes in the nanocrystal size alter both the electron and hole relaxation of photoexcited QDs but with very different extents. For instance, a more pronounced change in the hole relaxation was recorded in alkaline buffers and for green-emitting QDs compared to their red-emitting counterparts. We attributed these results to the more favorable electron transfer pathway from the reduced form of the complex to the valence band of the QD. This process benefits from the combination of lower oxidation potential and larger energy mismatch in alkaline buffers and for green-emitting QDs. In comparison, the effects on the rate of electron transfer from excited QDs to dopamine are less affected by QD size. These findings provide new insights into the mechanisms that drive charge transfer interactions and the ensuing quenching of QD emission in such assemblies.

Paper Details

Date Published: 12 March 2015
PDF: 8 pages
Proc. SPIE 9338, Colloidal Nanoparticles for Biomedical Applications X, 93380N (12 March 2015); doi: 10.1117/12.2077876
Show Author Affiliations
Xin Ji, Florida State Univ. (United States)
Nikolay S. Makarov, Los Alamos National Lab. (United States)
Wentao Wang, Florida State Univ. (United States)
Goutam Palui, Florida State Univ. (United States)
Istvan Robel, Los Alamos National Lab. (United States)
Hedi Mattoussi, Florida State Univ. (United States)

Published in SPIE Proceedings Vol. 9338:
Colloidal Nanoparticles for Biomedical Applications X
Wolfgang J. Parak; Marek Osinski; Xing-Jie Liang, Editor(s)

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