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A vibrant area of research within the Nanoscience group is the organisation of molecules on surfaces. Non-covalent interactions between molecules, through mechanisms such as hydrogen bonding and metal coordination, can be used to create supramolecular nanostructures with new and interesting properties.
The images on this page give some examples of the types of structures that can be created by the self-assembly of simple organic molecules.
Understanding why these structures form and what properties they have is of great value to researchers in fields as diverse as electro-optics, biophysics, and photolithography. Our work in this area is carried out in close collaboration with Prof. Neil Champness' group within the School of Chemistry at Nottingham.
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The DNA-base molecule adenine forms chiral domains on Ag-terminated Si(111) [1].
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(a) Cyanuric acid and melamine lattice on Au(111) [2], (b) Kinetic Monte Carlo simulations of 1D chain growth as observed with PTCDI molecules on the Ag-terminated Si(111) surface [3].
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PTCDI molecules (yellow) isolate melamine clusters (purple) on the Au(111) surface [4].
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We use the Scanning Tunneling Microscope (STM) as our primary tool for studying the formation of these nanostructures in both ultra high vacuum (UHV) and liquid environments. Recently installed facilities within the Nottingham Nanotechnology & Nanoscience Centre have also extended our studies from ambient to cryogenic temperature ranges. In addition to well-established deposition methods such as sublimation, we are currently developing an electrospray technique to deliver molecules directly from solution into the UHV environment.
There are many interesting topics to study in this fast-moving field of research. The competition between molecule-molecule and molecule-substrate interactions is one such area. By using a variety of substrates as platforms for self-assembly it is possible to explore this behaviour. We are currently investigating the templating properties of the boron nitride nanomesh as well as adsorption on more established surfaces such as Au(111) and graphite.
Another popular area of research is the development of supramolecular host-guest complexes on surfaces. Inspiration for this work can be traced back to the achievements of Donald Cram, Jean-Marie Lehn and Charles Pedersen who pioneered the field of supramolecular chemistry and were jointly awarded the Nobel Prize in 1987. Here at Nottingham we have demonstrated the trapping of fullerene molecules as guests within supramolecular networks.
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Host-guest interactions : Clusters of C60 trapped within the hexagonal pores of the melamine - PTCDI supramolecular network on Ag-terminated Si(111) [5].
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Relevant staff members : Prof. Peter Beton, Prof. Philip Moriarty, Dr. James O'Shea
References :
[1] L. M. A. Perdigão et al, Phys. Rev. B, 73, 195423 (2006)
[2] P. A. Staniec et al, J. Phys. Chem. C, 111, 886 (2007)
[3] J. Ben Taylor and P. H. Beton, Phys. Rev. Lett. 97, 236102 (2006)
[4] L. M. A. Perdigão et al, J. Phys. Chem. B, 110, 12539 (2006)
[5] J. A. Theobald et al, Nature, 424, 1029 (2003)
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