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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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Enhancement factor distribution of single Cy5 molecules on ZnO surfaces. The histogram was constructed from more than 50 molecules.
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f5-ijms-13-12100: Enhancement factor distribution of single Cy5 molecules on ZnO surfaces. The histogram was constructed from more than 50 molecules.

Mentions: The fluorescence emission rates of single probes on glass coverslips covered with ZnO were enhanced or remained the same on glass. A large distribution of single molecules shows as much as more than 10-fold increase in brightness when deposited on ZnO (Figure 5), which is in good agreement with ensemble experiment results. Zinc nanostructures have been reported to enhance emission of fluorophores [17–19] and such effects were ascribed to the enhanced absorption rate [17] in close proximity to zinc films and the possible changes in photonic mode density or reduction in self-quenching of fluorophores near ZnO nanostructures [18,19]. The exact mechanism governing the enhanced fluorescence on ZnO is still under investigating. In our approach, we assume the incident light is trapped by scattering so the effective intensity is increased, leading to enhanced fluorescence emission. The SEM image of ZnO film shows distinct features on the nanometer scale, making a heterogeneous environment available on the surface, as a result variation in brightness of the fluorophores was observed.


Photophysical behaviors of single fluorophores localized on zinc oxide nanostructures.

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

Enhancement factor distribution of single Cy5 molecules on ZnO surfaces. The histogram was constructed from more than 50 molecules.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5-ijms-13-12100: Enhancement factor distribution of single Cy5 molecules on ZnO surfaces. The histogram was constructed from more than 50 molecules.
Mentions: The fluorescence emission rates of single probes on glass coverslips covered with ZnO were enhanced or remained the same on glass. A large distribution of single molecules shows as much as more than 10-fold increase in brightness when deposited on ZnO (Figure 5), which is in good agreement with ensemble experiment results. Zinc nanostructures have been reported to enhance emission of fluorophores [17–19] and such effects were ascribed to the enhanced absorption rate [17] in close proximity to zinc films and the possible changes in photonic mode density or reduction in self-quenching of fluorophores near ZnO nanostructures [18,19]. The exact mechanism governing the enhanced fluorescence on ZnO is still under investigating. In our approach, we assume the incident light is trapped by scattering so the effective intensity is increased, leading to enhanced fluorescence emission. The SEM image of ZnO film shows distinct features on the nanometer scale, making a heterogeneous environment available on the surface, as a result variation in brightness of the fluorophores was observed.

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