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Detection of UltraTrace Concentrations of Explosives Using Fluorescent Polymers

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... used in military operations contain TNT ... of contaminants in TNT are dinitrotoluenes. Detecting ... detect concentrations of TNT in the parts per ... – PowerPoint PPT presentation

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Title: Detection of UltraTrace Concentrations of Explosives Using Fluorescent Polymers


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-thiop
hen-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/Brochure
    s_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/che
    mstry/chemstry.htm
  • http//www.umich.edu/navyrotc/NS202/Explosivesand
    Warheads.ppt
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