Catch that molecule!

Catch that molecule An array of self-assembled 'nano test-tubes'. The raised white areas represent seven C60 buckyballs enclosed within a single 'test-tube'.

Dr Neil Champness, Professor Martin Schroder, Dr Peter Hubberstey, Professor Peter Beton and Dr James O'Shea.
University of Nottingham.

Nanotechnology is a big 'buzz' word at the moment. This ground-breaking technology involves constructing and manipulating materials on the molecular scale to make new structures with novel properties. These nano-materials might lead to many exciting new applications, for example, storing huge amounts of information in tomorrow's computers, delivering clean sources of energy or structures that change their properties according to their environment. But how do scientists go about making such materials?

'A good first step would be to trap the molecules you want to work with in nanosized test-tubes', says Neil Champness. 'To do this you need to engineer the construction of surfaces or bulk materials to have openings, or pores, with dimensions of 1-10 nanometres (a nanometre is one billionth of a metre) - not an easy task.' The ideal solution would be to have a molecular scale 'Lego' kit that chemists could dip into to assemble customdesigned containers that perfectly fit the host molecules they want to work with.

Neil and his colleagues have started work on parts of the kit already using 'self assembly' processes. This involves designing molecules that use their own chemical properties to recognise other molecules and organise themselves into larger structures. 'The analogy in everyday life would be if we dropped a pile of bricks on the ground, which then spontaneously formed themselves into a patio or a wall', explains Neil.

When two chemicals (a triangular molecule called melamine and another rectangular molecule called PTCDI) are brought together on a silicon surface they prefer to bind to each other via hydrogen bonds rather than to themselves and the result is a honeycomb or grid of hexagonal holes. Each hole is only 3 nanometres across and just the right size to accommodate one 'buckyball' (or C60) molecule. The buckyballs sitting in their tiny 'test-tubes' can be viewed with a scanning tunnelling microscope (STM) - see image opposite. This sort of spontaneous surface structuring could serve as a platform for future nanotechnologies, such as molecular memory devices that could store information equivalent to a hundred DVDs on a surface just one or two centime

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