How does photochromic fluid work

  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.
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. See this thread and references within. Link
  4. 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

    Last edited by a moderator: Sep 25, 2014
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