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Fluorescence Spectroscopy for Studying Evaporating Droplets Using the Dye Eosin-Y.
Matthias Koegl1,2, Christoph Weiß1, Lars Zigan1,2
1Lehrstuhl für Technische Thermodynamik (LTT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany.
Sensors (Basel, Switzerland)
|October 27, 2020
Summary
Laser-induced fluorescence (LIF) spectroscopy is crucial for droplet sizing, but dye concentration and temperature affect accuracy. This study investigates dye enrichment effects on LIF signals in single droplets, revealing complex changes with evaporation and deformation.
Area of Science:
- Fluid dynamics
- Spectroscopy
- Physical chemistry
Background:
- Laser-induced fluorescence (LIF) spectroscopy is widely used for characterizing liquids and two-phase flows, including droplet sizing in sprays.
- Uncertainty in LIF measurements arises from varying dye concentration and temperature fluctuations during processes like mixing and evaporation.
- Systematic studies are needed to understand dye enrichment effects on LIF signals in single droplets.
Purpose of the Study:
- To investigate the influence of dye enrichment on the LIF signal of single droplets.
- To characterize the photophysical properties of Eosin-Y in water and ethanol under varying conditions.
- To analyze the effects of droplet evaporation, deformation, and concentration changes on LIF signals.
Main Methods:
- Spectrometric LIF setup and microcell for photophysical characterization of Eosin-Y solutions.
- Acoustic levitator to study single droplets under controlled conditions.
- Investigation of Eosin-Y in water and ethanol, common solvents in biomedical and power engineering.
Main Results:
- Eosin-Y in ethanol shows minimal temperature dependency up to 373 K, with negligible photodissociation.
- Eosin-Y in water exhibits significant photodissociation.
- Single droplet measurements revealed complex LIF signal variations with decreasing droplet size due to deformation and dye enrichment during evaporation.
Conclusions:
- Dye enrichment and droplet deformation significantly impact LIF signal intensity in evaporating droplets.
- Understanding these effects is critical for accurate droplet sizing and characterization using LIF.
- The choice of solvent (ethanol vs. water) influences dye stability and photodissociation, affecting LIF signal reliability.
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