Last updated on March 16, 2014 at 13:20 EDT  The Smallest
Conceivable Switch  December 12, 2011  Targeted proton transfer
within a molecule  For a long time miniaturization has been the
magic word in electronics. Dr. Willi Auwaerter and Professor
Johannes Barth, together with their team of physicists at the
Technische Universitaet Muenchen (TUM), have now presented a
novel molecular switch in the journal Nature Nanotechnology.
Decisive for the functionality of the switch is the position of
a single proton in a porphyrin ring with an inside diameter of
less than half a nanometer. The physicists can set four distinct
states on demand.  Porphyins are ring-shaped molecules that can
flexibly change their structure, making them useful for a wide
array of applications. Tetraphenylporphyrin is no exception: It
likes to take on a saddle shape and is not limited in its
functionality when it is anchored to a metal surface. The
molecule holds has a pair of hydrogen atoms that can change
their positions between two config