Technology could enable new chemical detection devices

Developed by scientists at Imperial College London, through research partly funded by the Defence Science and Technology Laboratory (DSTL) - part of the UK Ministry of Defence - the system is able to pick out a single target molecule from 10,000 trillion water molecules within milliseconds thanks to an effect called Surface Enhanced Raman Scattering (SERS) of light.

This technique exploits the way in which individual molecules each scatter light in a unique way. Previous research has shown that the signal can be amplified by catching molecules in a particular way on a layer of metal nanoparticles. However, these sheets are complex to manufacture. 

The team overcame this problem by dealing with interfaces of two liquids that do not mix, such as water and oil, or water and air interface. By manipulating the electrical charge of the gold nanoparticles and the composition of the solution, it was able 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.