Chemical detection technology, able to instantly spot tiny amounts of explosives, drugs or pollutants, could enable the development of a new generation of compact and easy-to-use detection devices for security services and the police.
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.
According to one of the researchers on the project, Michael Cecchini, the system’s sensitivity means that it could be used to look for small amounts of a specific molecule even in busy, public areas. A device based on the technology could also potentially be used to detect tiny traces of explosives or other illegal substances left behind by criminals on the surfaces they touch.