TY - JOUR
T1 - A fresh look into the time-resolved fluorescence of 8-hydroxy-1,3,6-pyrenetrisulfonate with the use of the fluorescence up-conversion technique
AU - Simkovitch, Ron
AU - Rozenman, Georgi Gary
AU - Huppert, Dan
N1 - Publisher Copyright:
© 2017
PY - 2017/7/1
Y1 - 2017/7/1
N2 - 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 H2O and D2O. 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, kPT, for HPTS in H2O and D2O is rather small 1010s−1 and 3.3 × 109s−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 τor = 80 ps in H2O, shorter than previously reported, whereas in methanol solution, with much lower viscosity, it is much larger – τor = 190 ps. We explain this large difference of τor by counter-ion association on all the three sulfonate groups of HPTS.
AB - 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 H2O and D2O. 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, kPT, for HPTS in H2O and D2O is rather small 1010s−1 and 3.3 × 109s−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 τor = 80 ps in H2O, shorter than previously reported, whereas in methanol solution, with much lower viscosity, it is much larger – τor = 190 ps. We explain this large difference of τor by counter-ion association on all the three sulfonate groups of HPTS.
KW - Excited state proton transfer
KW - Fluorescence up-conversion
KW - Geminate recombination
KW - Photoacid
KW - Time-resolved fluorescence
UR - http://www.scopus.com/inward/record.url?scp=85018428309&partnerID=8YFLogxK
U2 - 10.1016/j.jphotochem.2017.04.034
DO - 10.1016/j.jphotochem.2017.04.034
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:85018428309
SN - 1010-6030
VL - 344
SP - 15
EP - 27
JO - Journal of Photochemistry and Photobiology A: Chemistry
JF - Journal of Photochemistry and Photobiology A: Chemistry
ER -