Chapter 1 Applications of Luminescence to Fingerprints and Trace Explosives Detection

Fingerprints and trace explosives detection requires great sensitivity, which is provided by luminescence and appropriate physical and chemical treatments. Ninhydrin, 1,2-indanedione and other chemicals react with the amino acids present in the fingerprint residue. The chemically treated samples, on which the prints are to be detected, are excited with the blue lines 476.5 and 488 nm of an Argon laser, and the sample’s fluorescence is observed under orange filters. The detection of common explosives including trinitrotoluene (TNT) may also be carried out using luminescence techniques. Trace explosive and fingerprint detection require sensitivity due to the minute amount of matter left and available on the samples to be detected. Detection sensitivity can be gained by taking advantage of luminescence techniques. To increase the sensitivity of such detection luminescent chemicals are used, and to distinguish among compounds in a mixture of explosives, time-resolved imaging techniques may suppress any unwanted and background luminescence. Explosives are tagged with europium complexes showing long lived luminescence (3 ms) and appropriate for time-resolved imaging. The europium luminescence excitation utilizes a laser operating at 355 nm. Comparison between photoluminescence fingerprints and trace explosives detection will be presented and discussed: common difficulties will be exposed. key words: Laser, Luminescence, Time-resolved, Explosives, Detection, Fingerprints, 1,2-indanedione, Europium.