Luminescent inorganic polymer sensors for vapour phase and aqueous detection of TNT

Photoluminescent conjugated organic polymers have been applied to the detection of nitroaromatic explosives, such as TNT. The low energy unoccupied pi(*) orbitals in nitroaromatics can accept an electron from the excited state of luminescent polymers. This electron transfer quenching of luminescence provides detection limits as low as the parts per trillion (ppt) range. Photoluminescent organometallic polymetalloles and metallole copolymers have been synthesized and may also be used for the detection of nitroaromatic explosives such as picric acid, trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and nitrobenzene. These soluble polymers are extended oligomers with a degree of polymerization of about 10 to 20 metallole units, and show high sensitivity for detecting nitroaromatics in solution or the vapour phase. The efficiency of photoluminescence quenching follows the order TNT > DNT > nitrobenzene, which is correlated with their reduction potentials. Quenching of photoluminescence is primarily attributable to electron transfer from the lowest excited state of metallole polymers to the pi(*) LUMO of the nitroaromatic analyte. Quenching of photoluminescence is a static process, since the excited state lifetime is invariant with varying quencher concentration. Each metallole polymer has a unique ratio of quenching efficiency to the corresponding analyte and each analyte has a variety of different responses to different metallole polymers, which could be used to specify the analyte by pattern recognition methods. These inorganic polymers are robust and insensitive to common interferents, such as organic solvents and inorganic acids.