Direct fluorescence detects explosives

Few techniques can directly detect RDX and PETN, explosives that could be hidden in war zones and transportation hubs. Now, a new sensor can selectively identify these two common explosives by using a straightforward fluorescence method (J. Am. Chem. Soc. 2007, 129, 7254). Trisha L. Andrew and Timothy M. Swager at MIT developed the sensor, which is based on a photochemical reduction of RDX (1,3,5-trinitro-1,3,5-triazacyclohexane, a component of the explosive known as C-4) and PETN (pentaerythritol tetranitrate). The sensor design emerged from efforts to mimic an enzymatic reduction mediated by NADH (the reduced form of nicotinamide adenine dinucleotide). That reaction was previously discovered in a microbe that naturally destroys RDX in contaminated wastewater. An NADH mimic that the researchers designed was unstable, but it led them to a stable zinc analog (shown, Me is methyl). The analog exhibits 80- and 25-fold increases in emission intensity at 480 nm when it reacts in acetonitrile with RDX and PETN, respectively. The zinc compound does not react with the explosive 2,4,6-trinitrotoluene (TNT).