We carried out transient absorption spectroscopy of thioflavin T (ThT) molecules in various solvents employing an asynchronous optical sampling (ASOPS) scheme with dual synchronized and frequency up-converted mode-lock lasers in the near UV (NUV) spectral region. We developed a pair of synchronized femtosecond lasers with tunable center wavelengths ranging from 380 to 430 nm and spectral bandwidths of 30 nm. As a proof-of-principle experiment, we measured interferometrically detected time and frequency-resolved pump–probe signals of ThT in various solvents to study the twisted intramolecular charge transfer process of photo-excited ThT molecules. Both single-color NUV-NUV and two-color NUV-near IR (NIR) pump–probe measurements reveal that the vibronic coupling strengths of two vibrational modes with frequencies of 214 and 526 cm−1 in the excited state of ThT are reduced when ThT is dissolved in a chlorine-containing solvent, e.g., chloroform. We confirm theoretically that these vibrational modes have relatively high electric dipole moments in the excited state. As a result, the intramolecular charge transfer process of ThT in chloroform, which is driven by the solvation process of surrounding polar solvent molecules, could occur less efficiently, which results in an increase in the fluorescence quantum yield. Here, we demonstrate that the NUV-NUV and NUV-NIR ASOPS-transient absorption could be useful techniques for studying ultrafast photochemical reactions in condensed phases.
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14 February 2022
Research Article|
February 11 2022
Time-resolved spectroscopy of thioflavin T solutions: Asynchronous optical sampling method with two frequency-upconverted mode-locked lasers
Special Collection:
Time-resolved Vibrational Spectroscopy
Noh Soo Han;
Noh Soo Han
1
Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS)
, Seoul 02841, Republic of Korea
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JunWoo Kim;
JunWoo Kim
2
Department of Chemistry, Princeton University
, Princeton, New Jersey 08544, USA
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Tai Hyun Yoon
;
Tai Hyun Yoon
a)
1
Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS)
, Seoul 02841, Republic of Korea
3
Department of Physics, Korea University
, Seoul 02841, Republic of Korea
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Minhaeng Cho
Minhaeng Cho
b)
1
Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS)
, Seoul 02841, Republic of Korea
4
Department of Chemistry, Korea University
, Seoul 02841, Republic of Korea
b)Author to whom correspondence should be addressed: mcho@korea.ac.kr
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a)
E-mail: thyoon@korea.ac.kr
b)Author to whom correspondence should be addressed: mcho@korea.ac.kr
Note: This paper is part of the JCP Special Topic on Time-Resolved Vibrational Spectroscopy.
J. Chem. Phys. 156, 064201 (2022)
Article history
Received:
November 05 2021
Accepted:
January 27 2022
Citation
Noh Soo Han, JunWoo Kim, Tai Hyun Yoon, Minhaeng Cho; Time-resolved spectroscopy of thioflavin T solutions: Asynchronous optical sampling method with two frequency-upconverted mode-locked lasers. J. Chem. Phys. 14 February 2022; 156 (6): 064201. https://doi.org/10.1063/5.0077756
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