Neal
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Does anyone do phosphorescent experiments in sealed glass containers?
Sealed glass containers such as vials or even something as thin as a straw.
Where the oxygen is removed.
Reason being is oxygen is a quencher. More oxygen = more quenching of intensity and duration.
Glass, because you can shine light on it, then watch the thing phosphoresce.
Are there Youtube videos of this?
And even a comparison of the same compound but not in a sealed-glass environment, which would be exposed to oxygen and therefore weaker.
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walruslover69
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Yes. I did some academic research on organic phosphorescence and it's very common to measure with and without oxygen in a sealed atmosphere. Viscosity
can also play a role, as low viscosity tends to quench the excited state faster than high viscosity solvents. Depending on the material, it can have a
profound effect.
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Neal
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Quote: Originally posted by walruslover69  | | Yes. I did some academic research on organic phosphorescence and it's very common to measure with and without oxygen in a sealed atmosphere. Viscosity
can also play a role, as low viscosity tends to quench the excited state faster than high viscosity solvents. Depending on the material, it can have a
profound effect. |
Do these sealed glass vials or whatever are bought on-line?
I wouldn't mind a phosphorescent powder to lock in a skinny glass container.
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walruslover69
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We used special cuvettes similar to this. https://www.amazon.com/Fluorescence-Cuvette-Spectrophotomete...
Oxygen is more problematic for things in solution since the oxygen dissolves in it. In my experience the effect of oxygen is significantly less
noticeable with solids. I had great success mixing my phosphorescent compounds in a solvent with plastic (we used water and PVA) dropping it on a
glass slide and letting it dry to a thin film. While it won't be as impermeable to oxygen as sealing it in glass. Turning it into a a thin film
dispersed in plastic makes most samples more luminous. A cover slide similar to how a microscope slide is prepared would go a long way.
Sounds like an interesting project. What compounds are you work on?
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Lionel Spanner
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| Quote: Originally posted by walruslover69 | | Yes. I did some academic research on organic phosphorescence and it's very common to measure with and without oxygen in a sealed atmosphere. Viscosity
can also play a role, as low viscosity tends to quench the excited state faster than high viscosity solvents. Depending on the material, it can have a
profound effect. |
In a textbook I have on this subject (Turro's "Modern Molecular Photochemistry") experiments to determine the rate of phosphorescence were typically
carried out at liquid nitrogen temperature, which freezes the solvent.
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walruslover69
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Any excuse to work with liquid nitrogen is always a good one!
When cooled down to liquid nitrogen temperatures, a lot of compounds are phosphorescent that we don't normally consider to be. The main mechanism for
phosphorescence quenching is intra and intermolecular vibrational relaxation. The molecules are bouncing around, promoting each other into different
vibrational states and relaxing back down to the ground state. The result is the excited electron not staying in the stable triplet state where it
emits very slowly. For this reason there is a direct correlation between temperature and the excited state half life, which determines how long it
"glows". However this will be different for every compound and it's conditions.
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Neal
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| Quote: Originally posted by walruslover69 | Any excuse to work with liquid nitrogen is always a good one!
When cooled down to liquid nitrogen temperatures, a lot of compounds are phosphorescent that we don't normally consider to be. The main mechanism for
phosphorescence quenching is intra and intermolecular vibrational relaxation. The molecules are bouncing around, promoting each other into different
vibrational states and relaxing back down to the ground state. The result is the excited electron not staying in the stable triplet state where it
emits very slowly. For this reason there is a direct correlation between temperature and the excited state half life, which determines how long it
"glows". However this will be different for every compound and it's conditions. |
I'm more curious if there are things that don't phosphoresce at 25 C but do at 0 C.
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walruslover69
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There are probably very few compounds that phosphoresce at 0C but not 25C, just because it's such a small difference in thermal energy. Pretty much
everything that phosphoresces at 25C will emit brighter and longer at 0C. So you might find some things that don't emit at 25C, but emit very faintly
at 0C. I imagine there are some unicorn compounds out there that have a change in crystal structure or some other phenomenon that causes them to
abruptly become phosphorescent with that small of a temperature change. I am just not familiar with anything like this.
I made some carbon nanoparticles by pyrolyzing citric acid with an organic nitrogen compound (you can find lots of super easy microwave synthesis on
this) they emit phosphoresce, but the half life in water was so short it was imperceivable with a half life of ~200ns. However when we put it into the
PVA thin films I mentioned, the emission was faintly noticeable with a half life of a 10-50 microseconds. When that film was chilled to -10C to 0C in
our freezer, the half life was extended to almost 100 microseconds.
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Neal
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So what are some easy-to-buy or find phosphorescent compounds? Preferably a powder. That you can stick in a glass vial.
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walruslover69
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doped Zinc sulfide, Calcium Sulfide, Strontium aluminate. There are also lot's of naturally occurring minerals that are doped with impurities that
make them phosphorescent.
As for organic molecules, it gets a bit trickier since they are tons of them, but their half life's are on the scale of nanoseconds/microseconds and
not observable from the naked eye.
[Edited on 18-6-2024 by walruslover69]
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