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7 May 1997 Single-photon timing fluorometry using three-photon excitation
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Proceedings Volume 2980, Advances in Fluorescence Sensing Technology III; (1997)
Event: BiOS '97, Part of Photonics West, 1997, San Jose, CA, United States
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.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David A. Hatrick, Andreas Volkmer, Yanghong Bai, and David J. S. Birch "Single-photon timing fluorometry using three-photon excitation", Proc. SPIE 2980, Advances in Fluorescence Sensing Technology III, (7 May 1997);

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