Hi!

Does any chemical compound (which could be in liquid or solid state)
exist that emits light when the surrounding temperature rises up to a
specific temperature (no electricity is allowed to be involved)? I?m
mostly interested in compounds that behave like this in the lower
temperature scale, between 25 degrees Celsius (77 F) to 35 degrees
Celsius (95 F), please post any information that you can find even if
you find compounds that fall outside the above temperature range.
Chemiluminescence could be something to look into since these kinds of
mixtures light emitting properties are proportional to the surrounding
temperature. If you do that, please be aware of the fact that
chemiluminescence requires (from what I know) that two liquids first
be mixed together before light is sent out. My requirement on the
compound that I?m looking for is that no additional work (like mixing
two fluids) should be required; the compound should be ?as is?. The
compound should also be stable and have a ?shelf life? of at least 2-3
weeks and being non toxic.

If you would like to look in to the chemiluminescence area the
following links is a good starting point:
://www.google.com/answers/threadview?id=296954
http://science.howstuffworks.com/light-stick1.htm
http://www.complast.com/cyalume/cyalume_history.htm

If you need a clarification of the question, please don?t hesitate to
post some follow up questions!

Kind regards, 
Ralf.

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Clarification of Question by tindraswe-ga on 05 Sep 2004 10:03 PDT

Thanx for your comment crythias-ga!

I do have to make an adjustment of the temperature range I provided
before. The range that I'm looking for is between 30 degrees Celsius
(80 F)and 45 degrees Celsius (115 F). Sorry for providing the wrong
numbers earlier!

I can't make any specification of the brightness at the moment, I
don't need that kind of brightness usually provided by bulbs. A more
faded or dim light will be quite ok.

Neither UV, photoreactive or IR reactive should be a requirement on
the compound that I'm looking for.

I agree on the fact that thermoluminescence could be a better search
term than chemiluminescence, thx for your suggestion!

/Ralf

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Clarification of Question by tindraswe-ga on 05 Sep 2004 16:17 PDT

The most important factor is that the compound glow, the ability to
change color will be a nice add on but is not required. I can't be too
specific regarding the application unfortunately since that probably
would reveal too much about the business idea that I'm looking into.

I just realized that I need to clarify myself on the temperature issue
one more time. The compound should glow when the surrounding
temperature is equal to or higher than 30 degrees Celsius (80 F). It's
not a problem if the compound still glows when the temperature is
above 45 degrees Celsius (115 F), even if that is the maximum
temperature in which the product would operate in.

The "glow in the dark" stickers rely on phosphorescence to my
knowledge so the technique involved there is unfortunately not
applicable here. It should not be a requirement that the compound
first needs exposure to light (in any part of the spectrum) before
being able to glow. What I mean with this is that the end customer
that buy the product shouldn?t have this requirement on him/her, if
the compound needs to be prepared with light that would be ok if it
could be done in the production process of  the compound.

I do prefer (if I have the ability to choose) to find a solid compound
rather than a liquid. Maybe some kind of polymer could be found?

If nothing can be found with the requirements given above, then maybe
chemiluminescence needs to be considered again. A glow stick is
normally constructed as a plastic stick containing a small fragile
glass vial in the middle of the stick. An automatic mixture of the two
liquids contained in and outside the glass vial could maybe be
achieved if the glass was exchanged for another material that is
sensitive to heat above 30 degrees? Going above this temperature would
then mean that this material dissolves. It is important that this
material is not degraded by the surrounding liquids upon which the
chemiluminescent reaction is built. The ?shelf life? mentioned earlier
is still an important property.

/Ralf

It seems that you'd necessarily have to keep this in a refrigerator if
it worked at all, because your "shelf" room temperature is likely to
be the activation range.

Are you looking for any brightness at all? Or is color change at a
specific temperature significant enough? Would UV reactive or
photoreactive (or IR reactive?) at the temperature be acceptable?

I'd guess that if there was a way to make slightly-more-than-room
temperature luminescence, this would be very useful. I'd expect toy
manufacturers to be using this as well as this being something that,
similar to cyalume light sticks, you could shake to make the light
appear. The difference would be that the shaking would be friction
instead of mixing.

PS: Perhaps the search query is thermoluminescence. 
(spinach leaf) http://www.ias.ac.in/currsci/jun102003/1419.pdf
Some minerals that have thermoluminescent properties of 50 degrees
Celcius to 475 C http://mineral.galleries.com/minerals/pleochro.htm

I see a lot about thermoluminescent dosimeters. ... still not what
you're asking for. But, is color change adequate or does it really
need to glow? Can you provide a bit of info on application?

I keep thinking in my head about the "glow in the dark" stickers and
stars that a kid might put on his/her ceiling ... I realize this isn't
the same thing as well, but I wonder if it's on the same track or not?