William Trogler and his team at the University of California, San Diego have designed a super-sensitive spray-on explosive detector which can detect even a billionth of gram of explosive. They have designed a silafluorene-fluorene copolymer which can detect nitrogen-containing explosives at a much lower rate because it detects particles instead of explosive vapours. It works just as in CSI Miami, spray the polymer solution over the test area, let it dry, shine UV light on it, spots of explosive quench the fluorescent polymer and turn blue. The technology is being commercialized by a US security firm RedXDefense.

Initially, polymer-treated spots of both compounds appear blue under UV light, but after further exposure the trinitroglycerin spot fluoresces green-yellow whilst the TNT spot remains blue. This colour change is thought to be due to photooxidation of the fluorenyl groups of the polymer.

Trogler was surprised to find that adding a spirofluorene co-monomer gave the polymer a 100 per cent efficient conversion of UV light into fluorescence, describing this increase as dramatic. 'From a technology perspective, the most surprising thing was the ability to use photochemistry to attain a reasonably chemospecific turn-on sensor,' he says.

RSC via Slashdot