Back to Search
Start Over
Photophysics of Phenanthrene in Supercritical Carbon Dioxide. Solvent−Solute and Solute−Solute Interactions Revealed by Lifetime Distribution Analysis
- Source :
- The Journal of Physical Chemistry. 100:17931-17939
- Publication Year :
- 1996
- Publisher :
- American Chemical Society (ACS), 1996.
-
Abstract
- The exponential series method of analysis is applied to single photon counting measurements of phenanthrene fluorescence decay in supercritical carbon dioxide at 32 and 35 °C and at pressures ranging from 76 to 207 bar for chromophore concentrations between 5 × 10-5 and 5 × 10-6 M. The analysis revealed trimodal fluorescence lifetime distributions near the critical temperature which can be explained by the presence of solvent−solute and solute−solute clustering. This local aggregation causes an increase in nonradiative relaxations and, therefore, a decrease in the observed fluorescence lifetimes. Concentration and density gradients are responsible for these three unique lifetimes (trimodal) in the supercritical fluid, as contrasted with the single lifetime observed in a typical organic solvent. An increase in temperature to 35 °C induces no change in lifetime distributions at high chromophore concentration, but the trimodal distribution collapses to a single mode at lower concentrations, indicating that t...
Details
- ISSN :
- 15415740 and 00223654
- Volume :
- 100
- Database :
- OpenAIRE
- Journal :
- The Journal of Physical Chemistry
- Accession number :
- edsair.doi...........a391c919da80baf225c8056921f498d8