New method for self-assembling molecules

Posted on Friday, March 11th, 2011 in News, Publications| Share this article

Researchers at the University of Sheffield have discovered a new way of making small molecules self-assemble into complex nanopatterns, which will push the limits of what is possible in “bottom-up” methods of nanopatterning for advanced functional materials through molecular self-assembly.

The research, which was led by Dr Xiangbing Zeng and Professor Goran Ungar from the Department of Materials Science and Engineering, and colleagues from Martin Luther University Halle-Wittenberg in Germany, was published in Science today (11 March 2011).

The study opens the way to new methods of producing “bottom-up” ultra-small electronic and photonic integrated circuits. This would mean that instead of the expensive and slow electron, ion-beam or X-ray lithography, the molecules would assemble and form the desired patterns themselves. Today visible or UV light is still used, but how small a pattern can be made is limited by the wavelength of light, that is of the order of a micron.

The discovery was made after the researchers carried out X-ray diffraction on very thin films, using the beam of the Diamond Light Source synchrotron near Oxford. Other methods were also used to confirm the findings, such as neutron diffraction and atomic force microscopy.

The nanopatterns presented by the team are the most complex patterns in liquid crystals so far. The findings show how the molecules have formed liquid crystal honeycomb shapes with highly complex tiling patterns with cells of up to five different compositions or “colours” and five different polygonal shapes. The patterns have been formed by the molecules themselves finding the optimum stacking mode through countless trials and errors. A good understanding of the principles of self-assembly, gained by research such as this, will allow chemists to design molecules that would assemble precisely in the way they want.

Professor Goran Ungar from the Department of Materials Science and Engineering at the University of Sheffield, said: “These findings are a new step toward making molecules that will create complex molecular electronic and photonic devices spontaneously and en masse.”

Sheffield Media Centre