Structural transition in alcohol-water binary mixtures: A spectroscopic study |
| |
Authors: | Tuhin Pradhan Piue Ghoshal and Ranjit Biswas |
| |
Institution: | (1) Department of Chemical, Biological and Macromolecular Sciences, and Unit for Nanoscience and Technology, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata, 700 098, India |
| |
Abstract: | The strengthening of the hydrogen bonding (H-bond) network as well as transition from the tetrahedral-like water network to
the zigzag chain structure of alcohol upon increasing the alcohol concentration in ethanol-water and tertiary butanol (TBA)
— water mixtures have been studied by using both steady state and time resolved spectroscopy. Absorption and emission characteristics
of coumarin 153 (C153), a widely used non-reactive solvation probe, have been monitored to investigate the structural transition
in these binary mixtures. The effects of the hydrogen bond (H-bond) network with alcohol concentration are revealed by a minimum
in the peak frequency of the absorption spectrum of C153 which occur at alcohol mole fraction ∼0·10 for water-ethanol and
at ∼0·04 for water-TBA mixtures. These are the mole fractions around which several thermodynamic properties of these mixtures
show anomalous change due to the enhancement of H-bonding network. While the strengthening of H-bond network is revealed by
the absorption spectra, the emission characteristics show the typical non-ideal alcohol mole fraction dependence at all concentrations.
The time resolved anisotropy decay of C153 has been found to be bi-exponential at all alcohol mole fractions. The sharp change
in slopes of average rotational correlation time with alcohol mole fraction indicates the structural transition in the environment
around the rotating solute. The changes in slopes occur at mole fraction ∼0·10 for TBA-water and at ∼0·2 for ethanol-water
mixtures, which are believed to reflect alcohol mole fraction induced structural changes in these alcohol-water binary mixtures. |
| |
Keywords: | Alcohol-water binary mixtures hydrogen-bonding network structural transition absorption and fluorescence emission fluorescence anisotropy |
本文献已被 SpringerLink 等数据库收录! |
|