120th General Meeting of the KCS

Type Poster Presentation
Area Physical Chemistry
Room No. Exhibition Hall 2+3
Time 10월 20일 (금요일) 13:00~14:30
Code PHYS.P-113
Subject Photophysical properties of dyes in reverse micelles studied by time-resolved electronic spectroscopy
Authors Taehyung Jang, Gisang Lee, YOONSOO PANG1,*
Department of Chemistry, Gwangju Institute of Science and Technology, Korea
1Division of Physical Chemistry, Gwangju Institute of Science and Technology, Korea
Abstract Proton transfer or charge transfer is known as one of important chemical processes in many chemical and biological systems. Photo-induced proton and charge transfer occurring on ultrafast time scales have been of great interest in time-resolved spectroscopy. HPTS (8-hydroxypyrene-1,3,6-trisulfonic acid) is one of well-known photoacids. Its pKa value decreases greatly (7.7 → 0.5) when photo-excited and deprotonated HPTS shows distinct emission spectrum and kinetics compared to those of protonated HPTS. Another molecule is DNBP (4-Dimethylamino-4'-nitrobiphenyl) whose geometry in the ground state has a torsional angle of ~40 degree between two phenyl rings. Upon the photoexcitation, excited-state charge transfer occurs with the rotation of phenyl rings which are strongly dependent on the solvent polarity and viscosity. Emission spectra of DNBP show large Stokes shifts in polar solvent than nonpolar solvent. In this research, excited-state dynamics of HPTS and DNBP were investigated by time-correlated single photon counting (TCSPC) and femtosecond transient absorption spectroscopy. Fluorescence of HPTS and DNBP are strongly affected by solvent properties and local environments; dyes encapsulated in nano-pools of reverse micelles showed significant difference in emission spectra and kinetics compared to those in bulk phase. Emission spectra of HPTS in reverse micelles show a large change in the ratio of deprotonated species depending on the size of the nano-pools. Also emission spectra of DNBP in reverse micelles shift between the emission spectra of polar and nonpolar solvent. In addition, quantum yields of DNBP in the reverse micelles increase dramatically against the bulk phase.
E-mail taehyungjang@gist.ac.kr