World's smallest test tube
29 Nov 2004
David Britz and his colleagues at Oxford and Nottingham Universities have performed chemical reactions inside carbon nanotubes, hollow cylinders with nanoscale diameters.
The nanotube served as a confining environment for the researchers to initiate reactions between the molecules inside it and then directly observe the resulting material using an electron microscope.
It also allowed them to improve the way the molecules connected to each other. Without the tiny test tube, the molecules made up a twisted, branched polymer - but the tube seemed to have an ordering effect, forcing them into a linear chain.The nanotube has an inner diameter of approximately 1.2 nanometres, and a length of about 2 micrometers. Its volume is two zeptolitres (a zeptolitre is 10 to the power of -21 litres), and around 2,000 molecules react in that space.
The molecules used were Buckminster fullerene oxides (a 'buckyball' with a single oxygen atom attached), which were inserted into the nanotube in an inert environment. To initiate the reaction of polymerization, the material was heated. The tube affected the way the fullerenes connected to each other, forcing them into a line. This more ordered polymer was of much higher quality and the technique could evolve into a new way to make high-quality polymers.
Mr Britz said: 'Much of synthetic chemistry is about finding ways to make unfavourable reactions more favourable by changing environmental parameters. The inside of a nanotube is a new place to study chemical reactivity and may offer routes to synthesis of novel materials inaccessible by other means.'
The researchers would like to go on to see how other chemical reactions can be manifested inside confined spaces. They will also work on how to get the polymer product out of the nanotubes at the end of the reaction. 'We have some ideas for how to do it, but we have yet to find a suitable way,' said Mr Britz. 'Obviously if we wanted to one day use this technique to create materials, that's going to be pretty crucial.'
The full paper, 'Chemical reactions inside single-walled carbon nano test-tubes', by David A Britz, Andrei N Khlobystov , Kyriakos Porfyrakis , Arzhang Ardavan and G Andrew D Briggs, can be read online <link>here=http://www.rsc.org/CFmuscat/intermediate_abstract.cfm?FURL=/ej/CC/2005/B414247K/index.htm&TYP=ADV</link>.
