We are investigating the basic photophysics of novel, potential two-photon active photoinitiators (synthesized in the group of Prof. Liska, TU-Vienna). In the example shown here, we observe an interesting solvent dependence: in all solvents studied (polar and apolar), steady-state fluorescence is basically absent (quantum yield < 0.1%). However, broadband femtosecond time-resolved transient absorption reveals, that this low fluorescence quantum yield does not allow a priori conclusions about the "chemical reactivity" to be drawn.
Indeed, whereas the triplet state is populated very efficiently in apolar solvents, the singlet excited state decays via rapid internal conversion in polar solvents. Both pathways result in negligible fluorescence quantum yields. However, the photochemically "active" triplet state is efficiently populated in apolar solvents only.
Legend:
GSB ... ground state bleach
ESA ... excites state absorption
SE ... stimulated emission
| FOR MORE INFORMATION | ||
   |
||
Contact:
Eric Vauthey
Physical Chemistry Department - Sciences II - University of Geneva
30, Quai Ernest Ansermet - CH-1211 Geneva 4 (Switzerland)
© All rights reserved by Eric Vauthey and the University of Geneva
Design and code by Guillaume Duvanel