A fresh look into the time-resolved fluorescence of 8-hydroxy-1,3,6-pyrenetrisulfonate with the use of the fluorescence up-conversion technique
| Autor: | Dan Huppert, Ron Simkovitch, Georgi Gary Rozenman |
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| Rok vydání: | 2017 |
| Předmět: |
General Chemical Engineering
Cationic polymerization Analytical chemistry General Physics and Astronomy Protonation 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Fluorescence 0104 chemical sciences chemistry.chemical_compound Sulfonate Deprotonation Reaction rate constant chemistry Methanol Time-resolved spectroscopy 0210 nano-technology |
| Zdroj: | Journal of Photochemistry and Photobiology A: Chemistry. 344:15-27 |
| ISSN: | 1010-6030 |
| DOI: | 10.1016/j.jphotochem.2017.04.034 |
| Popis: | Steady-state and time-resolved fluorescence techniques were used to study the excited-state-proton-transfer (ESPT) process of 8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS) in H 2 O and D 2 O. In this contribution we use the fluorescence up-conversion technique with a time resolution of ∼100 fs to monitor the short-time components of HPTS ROH (protonated) and RO − (deprotonated) signals. The ESPT rate constant, k PT , for HPTS in H 2 O and D 2 O is rather small 10 10 s −1 and 3.3 × 10 9 s −1 , respectively. In the time-resolved fluorescence signal of the deprotonated form we find a rise-component of 2.5 ps which we assign to slow charge rearrangement as was already suggested by Spry and Fayer [Spry, D. B.; Fayer, M. D. Charge Redistribution and Photoacidity: Neutral Versus Cationic Photoacids. J. Chem. Phys . 2008 , 128, 084508-1–084508-9]. Already in the time-window of 0.2–1.2 ns, the proton geminate recombination (GR) fluorescence tail of the ROH form decays as t −α where α ≈ 3/2, as predicted by the diffusion-assisted GR model, but for much longer times ( t > 5 ns). We also found that the rotation-relaxation time of the ROH form is about τ or = 80 ps in H 2 O, shorter than previously reported, whereas in methanol solution, with much lower viscosity, it is much larger – τ or = 190 ps. We explain this large difference of τ or by counter-ion association on all the three sulfonate groups of HPTS. |
| Databáze: | OpenAIRE |
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