This
is extraordinary work. We now have a methodology to map not just the
atoms but also the nature of the bonds and likely electron locations
while we are at it. We have just gone from an idealized theoretical
model to a way more precise empirical framework in which the
anticipated variations can be actually seen. It does not get better
than this in terms of investigative chemistry. I suspect that any
deeper will be meaningless.
I do
not expect this to make a lot of difference in terms of work in
chemistry as the theory itself has been rather sufficient. It may
open nice questions in the theory though as we can now look and see.
We
should also see the special structure of biological water presently
ignored.
Atomic bond types
discernible in single-molecule images
13 September 2012
By Jason PalmerScience
and technology reporter, BBC News
A pioneering team from IBM in Zurich has published single-molecule
images so detailed that the type of atomic bonds between their
atoms can be discerned.
The same team took the
first-ever single-molecule image in 2009 and more recently published
images of a molecule shaped like the Olympic rings.
The new work opens
up the prospect of studying imperfections in the "wonder
material" graphene or plotting where electrons go during
chemical reactions.
The images are
published in Science.
The team, which
included French and Spanish collaborators, used a variant of a
technique called atomic force microscopy, or AFM.
AFM uses a tiny metal
tip passed over a surface, whose even tinier deflections are measured
as the tip is scanned to and fro over a sample.
The IBM team's
innovation to create the first single molecule picture, of a
molecule called pentacene, was to use the tip to pick up a single,
small molecule made up of a carbon and an oxygen atom.
This carbon monoxide
molecule effectively acts as a record needle, probing with
unprecedented accuracy the very surfaces of atoms.
It is difficult to
overstate what precision measurements these are.
The experiments must
be isolated from any kind of vibration coming from within the
laboratory or even its surroundings.
They are carried out
at a scale so small that room temperature induces wigglings of the
AFM's constituent molecules that would blur the images, so the
apparatus is kept at a cool -268C.
While some
improvements have been made since that first image of pentacene, lead
author of the Science study, Leo Gross, told BBC News that the new
work was mostly down to a choice of subject.
The new study examined
fullerenes - such as the famous football-shaped "buckyball"
- and polyaromatic hydrocarbons, which have linked rings of carbon
atoms at their cores.
The images show
just how long the atomic bonds are, and the bright and dark spots
correspond to higher and lower densities of electrons.
Together, this
information reveals just what kind of bonds they are - how many
electrons pairs of atoms share - and what is going on chemically
within the molecules.
"In the case of
pentacene, we saw the bonds but we couldn't really differentiate them
or see different properties of different bonds," Dr Gross said.
"Now we can
really prove that... we can see different physical properties of
different bonds, and that's really exciting."
The team will use the
method to examine graphene, one-atom-thick sheets of pure carbon that
hold much promise in electronics.
But defects in
graphene - where the perfect sheets of carbon are buckled or
include other atoms - are currently poorly understood.
The team will also
explore the use of different molecules for their "record
needle", with the hope of yielding even more insight into the
molecular world.
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