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Created
December 15, 2023 15:55
by
yqc5545
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Updated
December 15, 2023 15:55
by
[unknown user]
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December 15, 2023 15:57
by
yqc5545
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December 15, 2023 15:57
by
yqc5545
Description
Previous studies of water dynamics in hydrated Nafion® film utilizing various experimental techniques resulted in several different temperatures at which the water freezes in the hydrated Nafion® membrane. The goal of this project is to gain further insights into the low temperature water dynamics in this system by using luminescent probes in addition to differential scanning calorimetry technique. The asymmetry in peaks and enthalpies of water freezing and ice melting in the DSC thermogram indicates that a portion of water freezing starts at -38 °C; about 34 wt% of water is frozen at -65 °C and water continues to freeze as the temperature decreases to -150 °C. The thermogram also reveals that the frozen water in Nafion® membrane melts at -22 °C, which is consistent with the previously established fact that the water freezing and melting temperatures are sample size dependent. The emission spectra of *Ru(bpy)32+ embedded Nafion® film were captured from room temperature to -180 °C. Three crossovers (-30, -71, -105.5 ℃) were detected in the emission spectra maximum vs. temperature plot as shown in Figure 5; the first two can be attributed to some phase transition in the polymer membrane matrix while the third one can be attributed to the complete freezing of water inside the membrane. The photophysical properties of the PRODAN luminescent probe were analyzed in water-ethanol mixtures in the temperature range +25 to -150 °C. It was concluded that PRODAN can be used as a luminescent probe sensitive to water mobility. However, an attempt to use PRODAN as a luminescent probe for water dynamics in hydrated Nafion® membrane failed because Nafion® acted as a catalyst and PRODAN was degraded.
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Added Creator Yin-Jen Chang
December 15, 2023 15:57
by
yqc5545
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Added
LOW TEMPERATURE WATER DYNAMICS STUDY IN FULLY HYDRATED NAFION® MEMBRANE .pdf
December 15, 2023 16:00
by
yqc5545
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Deleted
LOW TEMPERATURE WATER DYNAMICS STUDY IN FULLY HYDRATED NAFION® MEMBRANE .pdf
December 15, 2023 16:11
by
yqc5545
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Added
LOW TEMPERATURE WATER DYNAMICS STUDY IN FULLY HYDRATED NAFION® MEMBRANE .pdf
December 15, 2023 16:11
by
yqc5545
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December 15, 2023 16:13
by
yqc5545
Description
- Previous studies of water dynamics in hydrated Nafion® film utilizing various experimental techniques resulted in several different temperatures at which the water freezes in the hydrated Nafion® membrane. The goal of this project is to gain further insights into the low temperature water dynamics in this system by using luminescent probes in addition to differential scanning calorimetry technique. The asymmetry in peaks and enthalpies of water freezing and ice melting in the DSC thermogram indicates that a portion of water freezing starts at -38 °C; about 34 wt% of water is frozen at -65 °C and water continues to freeze as the temperature decreases to -150 °C. The thermogram also reveals that the frozen water in Nafion® membrane melts at -22 °C, which is consistent with the previously established fact that the water freezing and melting temperatures are sample size dependent. The emission spectra of *Ru(bpy)32+ embedded Nafion® film were captured from room temperature to -180 °C. Three crossovers (-30, -71, -105.5 ℃) were detected in the emission spectra maximum vs. temperature plot as shown in Figure 5; the first two can be attributed to some phase transition in the polymer membrane matrix while the third one can be attributed to the complete freezing of water inside the membrane. The photophysical properties of the PRODAN luminescent probe were analyzed in water-ethanol mixtures in the temperature range +25 to -150 °C. It was concluded that PRODAN can be used as a luminescent probe sensitive to water mobility. However, an attempt to use PRODAN as a luminescent probe for water dynamics in hydrated Nafion® membrane failed because Nafion® acted as a catalyst and PRODAN was degraded.
License
- https://rightsstatements.org/page/InC/1.0/
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Published
December 15, 2023 16:13
by
yqc5545
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December 19, 2023 11:41
by
avs5190
Work Title
LOW TEMPERATURE WATER DYNAMICS STUDY IN FULLY HYDRATED NAFION® MEMBRANE
- Low Temperature Water Dynamics Study in Fully Hydrated Nafion® Membrane
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Updated
April 04, 2024 10:22
by
[unknown user]