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Proceedings Paper

Single-photon timing fluorometry using three-photon excitation
Author(s): David A. Hatrick; Andreas Volkmer; Yanghong Bai; David J. S. Birch
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Paper Abstract

We demonstrate the application of three photon excitation to fluorescence probe studies using time-correlated single- photon counting. By exciting with 120 fs Ti:sapphire laser pulses at 800 nm we have observed fluorescence emission from the scintillators p-Terphenyl (PT) and 2,1 Naphthyl, 5- Phenyloxazole ((alpha) -NPO). For solutions of (alpha) -NPO in cyclohexane and PT in propylene glycol the laser power dependence of the fluorescence is consistent with the emission being due to three-photon excitation of the same emitting S1 state which is populated with one-photon excitation at 267 nm. However, for (alpha) -NPO in alcohols some evidence for a mixture of three and two photon excitation is observed. This solute dependence correlates with the red edge of the one-photon absorption spectra. The observation of excimer emission and fluorescence anisotropy of (alpha) -NPO in small unilamellar vesicles (SUVs) of L- (alpha) -dipalmitoylphosphatidylcholine excited at 800 nm provides a clear illustration of the potential for using three photon excitation in fluorescence probe studies of microheterogeneous media. In SUVs the time-resolved data is consistent with a heterogeneous distribution of (alpha) -NPO molecules between isolated sites and ground state clusters in a similar manner to that which we reported previously for 2,5-diphenyloxazole.

Paper Details

Date Published: 7 May 1997
PDF: 11 pages
Proc. SPIE 2980, Advances in Fluorescence Sensing Technology III, (7 May 1997); doi: 10.1117/12.273545
Show Author Affiliations
David A. Hatrick, Univ. of Strathclyde (United Kingdom)
Andreas Volkmer, Univ. of Strathclyde (United Kingdom)
Yanghong Bai, Univ. of Strathclyde (United Kingdom)
David J. S. Birch, Univ. of Strathclyde (United Kingdom)

Published in SPIE Proceedings Vol. 2980:
Advances in Fluorescence Sensing Technology III
Richard B. Thompson, Editor(s)

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