How does photochromic fluid work

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In summary, when you switch between visible and IR light with LEDs, the colored half of the queens head on the English 5 pound note is reflecting IR while the other half is absorbing it.
  • #1
Hi all,
I purchased this photochromic fluid

I have been trying to get to the bottom of how it works.

From wikipedia

For example, the spiro form of an oxazine is a colorless leuco dye; the conjugated system of the oxazine and another aromatic part of the molecule is separated by a sp³-hybridized "spiro" carbon. After irradiation with UV light, the bond between the spiro-carbon and the oxazine breaks, the ring opens, the spiro carbon achieves sp² hybridization and becomes planar, the aromatic group rotates, aligns its π-orbitals with the rest of the molecule, and a conjugated system forms with ability to absorb photons of visible light, and therefore appear colorful. When the UV source is removed, the molecules gradually relax to their ground state, the carbon-oxygen bond reforms, the spiro-carbon becomes sp³ hybridized again, and the molecule returns to its colorless state.

So the when bond breaks and the ring opened does the red example above say then absorb all the frequencies except the photons of the red part of the spectrum we are seeing?

Any help gratefully received.
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  • #2
See this thread and references within. Link
  • #3
Hi Yanick, thanks for the link. I have read it and am assuming that the dye that has changed colour in my video is red for the same reasons a leaf is green. So the dye in my video to look red must it not be preferntially scattering photons of red wavelength into my eye and absorbing the photons with wavelengths in the visible part of the spectrum?

I have been removing the filters from web cams recently and an English 5 pound note has an interesting effect. Half the queens head is in a pigment that absorbs IR and the other half an ink that reflects it.
In this video I am switching between visible an IR with LEDs

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Related to How does photochromic fluid work

1. How does photochromic fluid change color?

Photochromic fluid contains molecules called photochromes that are sensitive to light. When exposed to UV or visible light, the molecules undergo a chemical reaction that causes them to change shape, which in turn changes the color of the fluid.

2. What causes photochromic fluid to change back to its original color?

The photochromic molecules have a reversible chemical reaction, meaning they can change shape back and forth. When the light source is removed, the molecules return to their original shape, and the fluid returns to its original color.

3. How long does it take for photochromic fluid to change color?

The time it takes for photochromic fluid to change color varies depending on the specific formula and the intensity of the light source. Generally, it can take anywhere from a few seconds to a few minutes for the color change to occur.

4. Can photochromic fluid be used in any color?

Yes, photochromic fluid can be made in a variety of colors, including clear, grey, blue, and green. However, the color change may not be as dramatic in darker colors due to the absorption of light.

5. Is photochromic fluid safe to use?

Yes, photochromic fluid is generally safe to use. However, as with any chemical substance, it is essential to follow proper safety precautions, such as wearing gloves and eye protection when handling and avoid ingestion or inhalation.

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