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“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

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

Presented By Allen Luebbe

overview
Overview
  • Brief history of explosives
  • General explosive knowledge
  • Energy of explosives
  • Chemical fingerprints
  • New fluorescent polymers
history of explosives
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
for a chemical to be an explosive it must exhibit all of the following
For A Chemical To Be An Explosive, It Must Exhibit All Of The Following
  • Formation of gases
  • Evolution of heat
  • Rapid rate of reaction
explosives
Explosives
  • Most explosives are organic compounds and contain multiple nitro groups
  • In addition to these compounds explosives properties they are also toxic to humans
categories of explosives
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)
nitro group
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
why do nitro groups lead to unstable compounds
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
energy of explosives
Energy of Explosives
  • Chemical explosives must provide a means to transfer heat energy to mechanical energy
energy of explosives1
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)

heat of explosion for tnt
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

slide14
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
chemical fingerprints
Chemical Fingerprints
  • Explosives emit chemical signatures called fingerprints
  • Each explosive has its own distinct chemical fingerprint
chemical fingerprint of tnt
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
detecting explosives
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.
chromophore
Chromophore
  • chemical group capable of selective light absorption resulting in the coloration of certain organic compounds.
advantages of polymer detector
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
synthesis of 5 bromo pyridin 2 yl 4 bromo thiophen 2 ylmethylene amine
Synthesis of (5-bromo-pyridin-2-yl)-(4-bromo-thiophen-2-ylmethylene)-amine
references
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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