Evolution and the nanoworld

With all the talk of self-assembly in nanotechnology, a group of German researchers has been looking in detail at the mechanism of molecular self-selection. The group’s findings give direct insight into the evolution of inanimate objects into living entities, and could prove useful in the development of new catalysts and surface applications.

Nanometre scale organisation of molecular components on a copper surface demonstrates sorting of two sizes of molecules through molecular self-selection

Scientists in the research groups of Klaus Kern at the Max Planck Institute for Solid State Research in Stuttgart (MPI), and Mario Ruben at the Forschungszentrum Karlsruhe (FZK), show how molecular organisation on surfaces can lead to membranes, cells, leaves, trees, and other biological structures.

Ruben’s team at FZK is responsible for designing molecules with built-in instructions which activate the self-selection process. Scientists at the MPI then observe self-selection in action by imaging grid-like assemblies of molecules which have sorted themselves by size.

“The molecular instructions are chemically coded in the molecular structure,” says Steven Tait of the MPI. “That is, the structure and interaction sites of the molecule determine what the resulting network pattern will be. When the molecules are thrown together on a surface, they know how to assemble themselves without further external guidance.”

In practical terms, what this means is that when we try to build, say, a template for a thin film photovoltaic, or an active catalyst array, it is possible to design molecules which will not only construct themselves into the planned structure, but will also sort themselves and correct errors along the way. “Without the self-selection step, we would simply have a disordered mess on the surface which would not be useful for complex nanotechnology problems,” says Tait.

“The beauty of this study is that the authors succeeded in visualising important concepts in supramolecular chemistry such as self-recognition and self-selection,” says Catholic University of Leuven chemist Steven de Feyter. “This pioneering study paves the way to investigate and visualise in detail fundamental dynamic processes in supramolecular chemistry.”

Further reading: Self-recognition and self-selection in multicomponent supramolecular coordination networks on surfaces, Langner et al., PNAS 104, 17927 (2007).

Figure: Nanometre scale organisation of molecular components on a copper surface demonstrates sorting of two sizes of molecules through molecular self-selection. The spacing between molecular rows is around 1 nm (source: Forschungszentrum Karlsruhe & Max-Planck-Institut für Festkörperforschung, Stuttgart).

Article first published in Nanomaterials News.