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“Detection of Ultra-Trace Concentrations of Explosives Using Fluorescent Polymers”

“Detection of Ultra-Trace Concentrations of Explosives Using Fluorescent Polymers”. Presented By Allen Luebbe. Overview. Brief history of explosives General explosive knowledge Energy of explosives Chemical fingerprints New fluorescent polymers. History of Explosives.

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“Detection of Ultra-Trace Concentrations of Explosives Using Fluorescent Polymers”

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  1. “Detection of Ultra-Trace Concentrations of Explosives Using Fluorescent Polymers” Presented By Allen Luebbe

  2. Overview • Brief history of explosives • General explosive knowledge • Energy of explosives • Chemical fingerprints • New fluorescent polymers

  3. History of Explosives • 1242 Roger Bacon publish optimum recipe for gunpowder • 1659 first ammonium nitrate synthesized by J.R. Glauber • 1846 Italian chemist Ascanio Sobrero synthesized nitroglycerine • 1866 Alfred Nobel invented dynamite • 1955 invention of ANFO • 2000 Philip Eaton synthesized octanitrocubane

  4. For A Chemical To Be An Explosive, It Must Exhibit All Of The Following • Formation of gases • Evolution of heat • Rapid rate of reaction

  5. Explosives • Most explosives are organic compounds and contain multiple nitro groups • In addition to these compounds explosives properties they are also toxic to humans

  6. Categories Of Explosives • High Explosives • Detonate (1000 to 8500m/s) • Differentiated by sensitivity • Primary - extremely sensitive to impact, heat, and friction • Secondary - less sensitive • Low Explosives • Used as propellants • Burn rapidly (up to 400m/s)

  7. Nitro Group • Many nitro compounds are unstable • The nitrogen atom is positively charged and each oxygen atom has a partial negative charge. • The nitro group has a powerful attraction for electrons

  8. Why do nitro groups lead to unstable compounds? • Nitrogen has charge of +1 and nitro groups have a strong tendency to withdraw electrons from other parts of the compound

  9. High Explosives

  10. Octanitrocubane

  11. Energy of Explosives • Chemical explosives must provide a means to transfer heat energy to mechanical energy

  12. Energy of Explosives • Total amount of energy released in an explosive reaction is called the heat of explosion • Calculated by comparing heats of formation before and after the reaction ∆E = ∆Ef(reactants) - ∆Ef(products)

  13. Heat Of Explosion for TNT ∆E = ∆Ef(reactants) - ∆Ef(products) ∆E = ∆Ef(-54.4kJ/mol) - ∆Ef(-670.8kJ/mol) ∆E = 616.4 kJ/mol ∆E > 0, rxn is exothermic (616.4 kJ/mol)(1000 J/1 kJ)(1 mol/227 g) = 2175 J/g

  14. TNT • Most commonly used explosive in landmines is TNT • Mines containing TNT or a mixture of TNT and other explosives accounts for 80% of all landmines manufactured world wide • 90% of landmines used in military operations contain TNT

  15. Compilation Of Explosives Used In Anti-personal Landmines

  16. Chemical Fingerprints • Explosives emit chemical signatures called fingerprints • Each explosive has its own distinct chemical fingerprint

  17. Chemical Fingerprint of TNT • Military grade TNT contains chemical contaminants • Contaminants are produced during the synthesis of TNT • Contaminants in TNT usually have a higher equilibrium vapor pressure than TNT • Examples of contaminants in TNT are dinitrotoluenes

  18. Detecting Explosives • Canines: canines can detect minute quantities for a variety of explosives. • Chemical Sensor: molecules are collected on a fiber and "ion mobility spectrometer" identifies type of explosive. • Neutron Beam: When neutrons contact contaminant, they instantly produce high energy gamma rays. Explosives are identified from energy of gamma rays. • Lasers: The interaction of laser radiation with traces of explosive causes micro bursts. Explosives are identified from light generated by bursts.

  19. Chromophore • chemical group capable of selective light absorption resulting in the coloration of certain organic compounds.

  20. Polymer detector

  21. Advantages of Polymer detector • Can detect concentrations of TNT in the parts per quadrillion • A single molecular binding event can change the fluorescence of an entire chain instead of just one molecule • Sensitivity of devices can be increased up to 10,000 times • Polymer receptor sites can be tuned to interact with only certain types of molecules

  22. Synthesis of (5-bromo-pyridin-2-yl)-(4-bromo-thiophen-2-ylmethylene)-amine

  23. Polymerization

  24. References • http://www.biochemtech.uni-halle.de/PPS2/projects/jonda/chromoph.htm • http://www.mn-net.com/web/ • Sheats, J. R. Science. 1997, 277, 191-192. • http://www.nomadics.com/Landmine_Detector/Brochures_white_papers/uxo2001.pdf • Chen, L; McBranch, D.; Wang, R.; Whitten, D. Chem Phys Lett., 330, 27-33, 2000. • http://www.fas.org/man/dod-101/navy/docs/es310/chemstry/chemstry.htm • http://www.umich.edu/~navyrotc/NS202/ExplosivesandWarheads.ppt

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