Research by scientists at The University of Nottingham has provided a bridge between the molecular world of chemistry and the fabrication of nanostructures.
The academics in the University’s Schools of Physics and Astronomy and Chemistry will report the new development in nanotechnology, in particular a branch known as bottom-up nanotechnology, in the science journal Nature this week.
In their work Dr Neil Champness and Professor Peter Beton, together with research students James Theobald and Neil Oxtoby, have come up with a method of making nanoscale containers that can be filled with small numbers of molecules.
The technique is based on using molecular building blocks that spontaneously arrange themselves into an array of nanoscale pores or containers with a width slightly less than three nanometres. This spontaneous assembly, sometimes referred to as self-assembly, is achieved by depositing the molecular building blocks of interest on a surface on which they can move around and lock into their preferred position.
Professor Peter Beton said: ‘This is analogous in the everyday world to emptying a pile of bricks onto the ground which then, instead of forming an unstructured heap, spontaneously arrange themselves into an ordered structure, for example, a wall or block paving.’
The molecular building blocks used at Nottingham come in two different sorts. One (melamine) is triangular while the other (a perylene derivative) is rectangular. The molecules are chosen so that the ends of the rectangular molecules stick to the edges of the triangular molecules, resulting in three rectangular molecules attach themselves to each triangular molecule. This process forms a honeycomb-like network that can then be used as an array of containers into which other molecules can be placed and stored.
The Nottingham team has demonstrated that each pore has the capacity for several large molecules. In their work they filled pores with buckyballs (C60, fullerenes). The buckyballs, which are trapped within a pore, interact and stick together to form a small hexagon.
The work demonstrates a breakthrough in bottom-up nanotechnology in which molecular components are assembled into larger structures and provides an alternative route to top-down nanotechnology. In the top-down approach small objects are fabricated by sculpting a large object, for example ‘chipping away’ until a sufficiently small feature or structure remains.
The Nottingham team believe that these nanoscale containers – or nano test tubes – may be filled with a wide variety of alternative atoms and molecules leading to the assembly of a wide range of new nanostructures.