A Spectroscopic and Computational Exploration of the Cybotactic Region of Gas-Expanded Liquids: Methanol and Acetone
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- 作者：John L. Gohres ; Christopher L. Kitchens ; Jason P. Hallett ; Alexander V. Popov ; Rigoberto Hernandez ; Charles L. Liotta ; Charles A. Eckert
- 刊名：Journal of Physical Chemistry B
- 出版年：2008
- 出版时间：April 17, 2008
- 年：2008
- 卷：112
- 期：15
- 页码：4666 - 4673
- 全文大小：386K
- 年卷期：v.112,no.15(April 17, 2008)
- ISSN：1520-5207
文摘
Local compositions in supercritical and near-critial fluids may differ substantially from bulk compositions,and such differences have important effects on spectroscopic observations, phase equilibria, and chemicalkinetics. Here, we compare such determinations around a solute probe dissolved in CO2-expanded methanoland acetone at 25 
C from solvatochromic experiments with molecular dynamics simulations. UV/vis andsteady-state fluorescence measurements of the dye Coumarin 153 in the expanded liquid phase indicatepreferential solvation in both the S0 and S1 states by the organic species. Simple dielectric continuum modelsare used to estimate local compositions from the spectroscopic data and are compared to molecular dynamicssimulations of a single C153 molecule dissolved in the liquid phase at bubble point conditions. The simulationsprovide information about the local solvent structure around C153. They suggest the presence of large solventclustering near the electron-withdrawing side of the probe. Preferential solvation exists in both the S0 and S1states, but a large disagreement between simulation and experiment exists in the S1 state. Potential reasonsfor this disparity are discussed.
C from solvatochromic experiments with molecular dynamics simulations. UV/vis andsteady-state fluorescence measurements of the dye Coumarin 153 in the expanded liquid phase indicatepreferential solvation in both the S0 and S1 states by the organic species. Simple dielectric continuum modelsare used to estimate local compositions from the spectroscopic data and are compared to molecular dynamicssimulations of a single C153 molecule dissolved in the liquid phase at bubble point conditions. The simulationsprovide information about the local solvent structure around C153. They suggest the presence of large solventclustering near the electron-withdrawing side of the probe. Preferential solvation exists in both the S0 and S1states, but a large disagreement between simulation and experiment exists in the S1 state. Potential reasonsfor this disparity are discussed.