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Preparation of Binary and Ternary Deep Eutectic Systems
Published on: October 31, 2019
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Pyrene Fluorescence To Probe a Lithium Chloride-Added (Choline Chloride + Urea) Deep Eutectic Solvent
Divya Dhingra1, Bhawna1, Ashish Pandey1
1Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas , New Delhi 110016 , India.
The Journal of Physical Chemistry. B
|March 28, 2019
Summary
Deep eutectic solvents (DESs) like Reline, mixed with LiCl, show stable properties with temperature changes. The addition of LiCl influences pyrene
Area of Science:
- Physical Chemistry
- Materials Science
- Electrochemistry
Background:
- Deep eutectic solvents (DESs) offer sustainable and cost-effective alternatives to conventional electrolytes.
- Reline, a DES composed of choline chloride and urea, is a promising medium for various applications.
- Understanding the behavior of DESs with added salts is crucial for optimizing their performance.
Purpose of the Study:
- To investigate the effect of lithium chloride (LiCl) on the physicochemical properties of the DES Reline.
- To explore the influence of temperature and LiCl concentration on the photophysical behavior of pyrene within Reline.
- To elucidate the quenching dynamics of pyrene in LiCl-Reline mixtures.
Main Methods:
- Utilized multidimensional fluorescence spectroscopy with pyrene as a probe.
- Measured pyrene's emission intensity ratio (I1/I3) to assess medium dipolarity.
- Analyzed excited-state decay kinetics and Stern-Volmer quenching with nitromethane.
- Investigated temperature effects (298.15–358.15 K) and varying LiCl concentrations (up to 2.093 m).
Main Results:
- LiCl addition did not significantly alter Reline's dipolarity but moderated temperature-induced changes.
- Pyrene's excited-state decay followed a two-exponential model, with longer decay times decreasing with temperature.
- Chloride ions (Cl-) from LiCl enhanced non-radiative decay pathways of excited pyrene.
- Bimolecular quenching rate constants (kq) initially increased then decreased with LiCl concentration, linked to viscosity and Cl- effects.
Conclusions:
- LiCl modifies the microenvironment and quenching dynamics within Reline without drastically changing its bulk properties.
- The interplay between viscosity, chloride ions, and temperature dictates the quenching efficiency in these DES-based electrolytes.
- DESs like Reline, when doped with salts, present tunable properties for advanced electrochemical applications.
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