A sensor that can rapidly detect the chemical nerve agent Sarin has been developed by US scientists. 

Sarin, which is a liquid at room temperature, evaporates quickly to give a colourless and odourless gas.  It attacks the nervous system of humans and was used in the terrorist attack on the Tokyo subway in 1995.  

'In today's political climate, the threat of terrorist activity is ever more prevalent.and the detection of chemical nerve agents is imperative,' said Eric Anslyn, a chemist at the University of Texas, Austin. This prompted Anslyn and colleagues to design a molecule that reacts with a sarin surrogate, a chemically similar but safer proxy for sarin, in mere milliseconds.

'The sensor is able to switch on a fluorescence signal very rapidly, upon the detection of chemical nerve agents,' said Anslyn.  

Previous methods for detecting chemical warfare agents involve the reaction of an alcohol with the agent, which is an intrinsically slow reaction, explained Anslyn. The detection system used by the new sensor much faster, with a reaction half life of 50 milliseconds.

The sensor is based on the dye molecule coumarin, which carries an oximate functional group. An electron pair on the oximate group normally quenches the fluorescent part of the coumarin so that the dye molecule does not fluoresce. But when the oximate group reacts with the sarin surrogate, the fluorescence of the dye is turned on.

'The next stage is to attach these particular molecules onto the surface of solid supports for the development of a device,' said Anslyn.  

Alison Stoddart