Understanding the redox coupling between quantum dots and the neurotransmitter dopamine in hybrid self-assemblies

Xin Ji; Nikolay S. Makarov; Wentao Wang; Goutam Palui; Istvan Robel; Hedi Mattoussi

doi:10.1117/12.2077876

12 March 2015 Understanding the redox coupling between quantum dots and the neurotransmitter dopamine in hybrid self-assemblies

Xin Ji, Nikolay S. Makarov, Wentao Wang, Goutam Palui, Istvan Robel, Hedi Mattoussi

Author Affiliations +

Proceedings Volume 9338, Colloidal Nanoparticles for Biomedical Applications X; 93380N (2015) https://doi.org/10.1117/12.2077876
Event: SPIE BiOS, 2015, San Francisco, California, United States

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.

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Xin Ji, Nikolay S. Makarov, Wentao Wang, Goutam Palui, Istvan Robel, and Hedi Mattoussi "Understanding the redox coupling between quantum dots and the neurotransmitter dopamine in hybrid self-assemblies", Proc. SPIE 9338, Colloidal Nanoparticles for Biomedical Applications X, 93380N (12 March 2015); https://doi.org/10.1117/12.2077876

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KEYWORDS

Picosecond phenomena

Absorption

Luminescence

Neurotransmitters

Nanocrystals

Quantum dots

Dispersion

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