With the current rise in terrorist activity comes a renewed interest in the detection of possible chemical weapons. Commonly used chemicals are of particular interest because of their potential availability to terrorist organisations. Scientists have now developed a fast way of detecting phosgene (C(O)Cl₂), a poisonous gas used extensively in manufacturing industries. Phosgene was the major cause of chemical deaths among troops in the First World War.

Phosgene is a colourless gas that targets the lungs, eyes and skin. Though highly toxic, not everybody can smell it at low concentrations and the effects of exposure can take hours to appear. 

Phosgene sensors typically use electrochemical or laboratory-based spectroscopic techniques. Dmitry Rudkevich and Hexiang Zhang from the University of Texas at Arlington, US, have now used fluorescence resonance energy transfer (FRET) to detect this compound. Fluorescence occurs within seconds of adding triphosgene to a dye mixture. 

Angel Kaifer, an expert in supramolecular chemistry at the University of Miami, Florida, US, described the work as a 'very simple but elegant approach for the sensing and detection of this dangerous chemical'. 

The method relies on a mixture of two fluorescent dyes. Shining light on the mixture at a wavelength of 343nm causes fluorescence at 464nm only when phosgene is present to link the two dye molecules. This is because the phosgene link causes the two molecules to be separated by only 20Å, allowing energy transfer between them.

Rudkevich, an associate professor of organic chemistry, says the detection procedure can be quantitative as well as qualitative. His research group is currently working on lowering the detection limit by investigating other dye mixtures. 

Freya Mearns