Chemists develop device to isolate single target molecule

According to the chemists, this technology will help lead to the development of other compact, easy-to-assemble and reusable devices. It will be easier and faster to detect various pollutants in rivers, nerve gases released into the air or even illegal drugs. The researchers said that the device could even be used to capture criminals who fail to wipe out all traces they leave behind. This latest technology could also benefit law enforcers whose job it is to identify activities that involve illegal substances.

Said one of the authors of the study, Michael Cecchini from the Department of Chemistry at Imperial College London: 'Our system could solve a key problem of reliable and portable chemical testing for use in the outside world. It is very sensitive and could well be used to look for very small amounts of a specific molecule even in busy, public areas.'

The team said the effect Surface Enhanced Raman Scattering (SERS) of light identifies the target molecules. According to them, this near-40-year-old technique works because each molecule scatters light in a unique way. Past studies found that the signal can be amplified by catching molecules in a particular way on a layer of metal nanoparticles. But, it is not easy to make these sheets.

To get the results they needed, the scientists dealt with interfaces of two liquids that do not mix, such as water and oil, or water and air interface. They manipulated the electrical charge of the gold nanoparticles and the composition of the solution to create a situation where the particles line themselves up at the interface between the two non-mixable liquids, or between a liquid and the air, they said.

'The trick to achieving this system's sensitivity to the target molecules was in finding the conditions at which nanoparticles would settle at the interface at close distances to each other without fusing together,' said co-author Jack Paget.

Vladimir Turek, another research team member and co-author, said: 'The system shows real promise for detectors for use in rough outdoor environmental and defence applications, since the liquids and nanoparticles can be easily replaced to regenerate the device.'

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Imperial College London:  http://www3.imperial.ac.uk/

Nature Materials:  http://www.nature.com/nmat/index.html