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Photophysical behaviors of single fluorophores localized on zinc oxide nanostructures.

Fu Y, Zhang J, Lakowicz JR - Int J Mol Sci (2012)

Bottom Line: In this report we studied photophysical behaviors of single fluorophores in proximity to zinc oxide nanostructures by single-molecule fluorescence spectroscopy and time-correlated single-photon counting (TCSPC).Single fluorophores on ZnO surfaces showed enhanced fluorescence brightness to various extents compared with those on glass; the single-molecule time trajectories also illustrated pronounced fluctuations of emission intensities, with time periods distributed from milliseconds to seconds.The fluorescence fluctuation dynamics were found to be inhomogeneous from molecule to molecule and from time to time, showing significant static and dynamic disorders in the interfacial electron transfer reaction processes.

View Article: PubMed Central - PubMed

Affiliation: Center for Fluorescence Spectroscopy, Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland School of Medicine, 725 Lombard Street, Baltimore, MD 21201, USA; E-Mails: jianzhang@umaryland.edu (J.Z.); jlakowicz@umaryland.edu (J.R.L.).

ABSTRACT
Single-molecule fluorescence spectroscopy has now been widely used to investigate complex dynamic processes which would normally be obscured in an ensemble-averaged measurement. In this report we studied photophysical behaviors of single fluorophores in proximity to zinc oxide nanostructures by single-molecule fluorescence spectroscopy and time-correlated single-photon counting (TCSPC). Single fluorophores on ZnO surfaces showed enhanced fluorescence brightness to various extents compared with those on glass; the single-molecule time trajectories also illustrated pronounced fluctuations of emission intensities, with time periods distributed from milliseconds to seconds. We attribute fluorescence fluctuations to the interfacial electron transfer (ET) events. The fluorescence fluctuation dynamics were found to be inhomogeneous from molecule to molecule and from time to time, showing significant static and dynamic disorders in the interfacial electron transfer reaction processes.

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(a) The typical decay curves on glass (green line) and on ZnO surface (red line); (b) Lifetime histograms of single Cy5 molecules on glass (top, gray) and ZnO covered glass (bottom, dark). Red line: Gaussian fits. The histograms are constructed from more than 50 molecules on glass and ZnO, respectively.
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f6-ijms-13-12100: (a) The typical decay curves on glass (green line) and on ZnO surface (red line); (b) Lifetime histograms of single Cy5 molecules on glass (top, gray) and ZnO covered glass (bottom, dark). Red line: Gaussian fits. The histograms are constructed from more than 50 molecules on glass and ZnO, respectively.

Mentions: where Γ and knr are the radiative and non-radiative decay rate, respectively. Suppose a fluorophore displays a low quantum yield, which implied knr >> Γ, as the value of Γ increases, the lifetime decreases. The changes in knr are typically due to changes in an emitter’s environment, quenching or resonance energy transfer (RET). The radiative decay rate Γ is constant and the changes are primarily due to changes in dielectric constant. Many fluorescence decays of single Cy5 molecules on glass can be fitted to a single component exponential function and the measured lifetimes are equal to the intrinsic lifetime. Figure 6 shows examples of time-resolved decay curves derived from trajectories illustrated in Figure 2c,e, respectively. The fluorescence intensity decays were analyzed in terms of the multi-exponential model as the sum of individual single exponential decays [44]:


Photophysical behaviors of single fluorophores localized on zinc oxide nanostructures.

Fu Y, Zhang J, Lakowicz JR - Int J Mol Sci (2012)

(a) The typical decay curves on glass (green line) and on ZnO surface (red line); (b) Lifetime histograms of single Cy5 molecules on glass (top, gray) and ZnO covered glass (bottom, dark). Red line: Gaussian fits. The histograms are constructed from more than 50 molecules on glass and ZnO, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3472795&req=5

f6-ijms-13-12100: (a) The typical decay curves on glass (green line) and on ZnO surface (red line); (b) Lifetime histograms of single Cy5 molecules on glass (top, gray) and ZnO covered glass (bottom, dark). Red line: Gaussian fits. The histograms are constructed from more than 50 molecules on glass and ZnO, respectively.
Mentions: where Γ and knr are the radiative and non-radiative decay rate, respectively. Suppose a fluorophore displays a low quantum yield, which implied knr >> Γ, as the value of Γ increases, the lifetime decreases. The changes in knr are typically due to changes in an emitter’s environment, quenching or resonance energy transfer (RET). The radiative decay rate Γ is constant and the changes are primarily due to changes in dielectric constant. Many fluorescence decays of single Cy5 molecules on glass can be fitted to a single component exponential function and the measured lifetimes are equal to the intrinsic lifetime. Figure 6 shows examples of time-resolved decay curves derived from trajectories illustrated in Figure 2c,e, respectively. The fluorescence intensity decays were analyzed in terms of the multi-exponential model as the sum of individual single exponential decays [44]:

Bottom Line: In this report we studied photophysical behaviors of single fluorophores in proximity to zinc oxide nanostructures by single-molecule fluorescence spectroscopy and time-correlated single-photon counting (TCSPC).Single fluorophores on ZnO surfaces showed enhanced fluorescence brightness to various extents compared with those on glass; the single-molecule time trajectories also illustrated pronounced fluctuations of emission intensities, with time periods distributed from milliseconds to seconds.The fluorescence fluctuation dynamics were found to be inhomogeneous from molecule to molecule and from time to time, showing significant static and dynamic disorders in the interfacial electron transfer reaction processes.

View Article: PubMed Central - PubMed

Affiliation: Center for Fluorescence Spectroscopy, Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland School of Medicine, 725 Lombard Street, Baltimore, MD 21201, USA; E-Mails: jianzhang@umaryland.edu (J.Z.); jlakowicz@umaryland.edu (J.R.L.).

ABSTRACT
Single-molecule fluorescence spectroscopy has now been widely used to investigate complex dynamic processes which would normally be obscured in an ensemble-averaged measurement. In this report we studied photophysical behaviors of single fluorophores in proximity to zinc oxide nanostructures by single-molecule fluorescence spectroscopy and time-correlated single-photon counting (TCSPC). Single fluorophores on ZnO surfaces showed enhanced fluorescence brightness to various extents compared with those on glass; the single-molecule time trajectories also illustrated pronounced fluctuations of emission intensities, with time periods distributed from milliseconds to seconds. We attribute fluorescence fluctuations to the interfacial electron transfer (ET) events. The fluorescence fluctuation dynamics were found to be inhomogeneous from molecule to molecule and from time to time, showing significant static and dynamic disorders in the interfacial electron transfer reaction processes.

Show MeSH
Related in: MedlinePlus