Friday, August 28, 2009

Zoom in on molecules at last

Thanks to specialised microscopes, we have long been able to see the beauty of single atoms. But strange though it might seem, imaging larger molecules at the same level of detail has not been possible – atoms are robust enough to withstand existing tools, but the structures of molecules are not. Now researchers at IBM have come up with a way to do it.

The earliest pictures of individual atoms were captured in the 1970s by blasting a target – typically a chunk of metal – with a beam of electrons, a technique known as transmission electron microscopy (TEM).

Later refinements of this technique, such as the TEAM project at the Lawrence Berkeley National Laboratory in California achieved resolutions of less than the radius of a single hydrogen atom. But while this method works for atoms in a lattice or thin layer, the electron bombardment destroys the arrangement of atoms in molecules.

Other techniques use a tiny stylus-like scanning probe to explore the atom-scale world. One method uses such a probe to measure the charge density associated with individual atoms – a technique called scanning tunnelling microscopy (STM).

Another, called atomic force microscopy (AFM), measures the attractive force between atoms in the probe and the target. The image is created by bumping the probe over the atoms of the molecule – much in the way we might feel our way around in a dark bedroom.

Source: New Scientist


Post a Comment