Detection of ultra trace concentrations of explosives using fluorescent polymers
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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”

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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


High explosives

High Explosives


Octanitrocubane

Octanitrocubane


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


Detection of ultra trace concentrations of explosives using fluorescent polymers

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


Compilation of explosives used in anti personal landmines

Compilation Of Explosives Used In Anti-personal Landmines


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.


Polymer detector

Polymer detector


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


Polymerization

Polymerization


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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