A fluorescent chemosensor to detect saturated nitramine and nitrate ester explosives was devised based on a photochemical reduction reaction. 10-Methyl-9,10-dihydroacridine (AcrH(2)) was found to transfer a hydride ion equivalent to the high explosives RDX and PETN upon irradiation at 313 nm in degassed acetonitrile solutions. Mechanistic photophysical studies indicate that the photoreduction of RDX proceeds via a two-step electron-hydrogen atom transfer reaction, whereas PETN photoreduction proceeds via a three-step electron-proton-electron transfer sequence. A zinc analogue was synthesized and found to display an 80- or 25-fold increase in 480 nm emission intensity upon reaction with RDX or PETN, respectively. Moreover, the Zn analogue was found to be unresponsive to TNT and other common contaminants, in addition to being photostable under ambient conditions. On the basis of these characteristics, we report a powerful chemosensor that displays a direct fluorescent response to either RDX or PETN.