Re: Do you know of any materials whose color may be controlled electrically?

Sorry, I dont know any now, other than things like neon which light up when 
excited.  I'll have to do some research, and it might take some time

I havent been able to find anything on this one.  Interesting property, but 
nothing listed in any of my resources.

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Admin note:

Marc Breen adds the following:

Alan,

The phenomenon to which you are referring is called electroluminescence
[electro = electricity; luminescence = gives off light].  Many compounds
can be "excited" by absorbing electrical energy.  During excitation, an
electron in its lowest energy state (involved in bonding) might move to a
higher energy state (an antibonding orbital).  In such a scenario, an
electron involved in bonding might be located between and shared by the
nuclei of two atoms.  If you relocate that electron to the other side of
one of the atoms (or to an orbital further out from the nucleus), that
will weaken the bond between the two atoms.  These are called anti-bonding
orbitals because when an electron is moved into one of them, the molecule
starts to pull apart.  This is a very unstable situation, so the electron
tries to "relax" by losing its energy.  It can do this by releasing the
energy in the form of heat and/or light.  There are a variety of
semiconductor materials such as zinc sulfide (ZnS) or zinc selenide
(ZnSe), when doped with a small amount of manganese (Mn), which are
electroluminescent.  Typically you are stuck with one color.  You can't
really change the color by flipping a switch.  However, there are some
tricks that you can pull.  There is another phenomenon referred to as
"quantum confinement."  Basically, when you shrink semiconducting
particles down to the nanometer scale (smaller than the wavelengths of
visible light) a lot of strange things happen.  Below a certain point, you
can change the color of the light observed by changing the diameter of the
particles (i.e. small particles = red light; really, really small
particles = blue light).  This is really cutting edge stuff and the
reasons why are far too complex to go into at this time, but if
you are interested look up material on "quantum dots."

Slan,


Marc