Compositional Study of Different Currency Coins Using Non-Destructive Laser Induced Breakdown Spectroscopy

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Compositional Study of Different Currency Coins
Using Non-Destructive Laser Induced Breakdown
Spectroscopy
2nd SASC Muharram, 1425 Jeddah, KSA
Zain Yamani, Ph.D. Physics Department KFUPM
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Presentation plan

• Introduction What is LIBS?
• Different physical methods for material analysis.
• What is special about LIBS?
• Compositional determination of coins using LIBS
• a- Experimental set-up
• b- Results
• c- Conclusions
• Concluding remarks

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Introduction
LIBS Laser Induced Breakdown Spectroscopy
LIBS is an analytical method by which one can
determine (qualitatively and quantitatively) the
elemental composition of solid, liquid or gas
samples.

• LIBS
• focused laser pulses
• vaporize, atomize and excite the sample
• plasma emission
• collect, disperse and analyze light
• atomic spectral lines determine the elemental
  composition

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What other methods are used for elemental analysis
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How does LIBS compare with other analytical
methods?

• Micro-LIBS
• Portability
• Rapid
• NDT

• Different types of samples
• Little sample preparation
• No (chemical) waste

This is not to say that there are no
complications in LIBS. Of course, there are!
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What is LIBS used for? (applications, from the
literature)

• Environmental monitoring to measure soil
  contamination (Zolotovitskaya et al., 1997)
• Detect toxic metals (Yamamoto et al., 1996
  Buckley et al., 2000)
• Study the chemical compositions in liquids (Yueh
  et al., 2002 Samek et al., 2000)
• Study the chemical compositions in polymers
  (Sattmann et al., 1998)
• In forensics and military applications (Kincade,
  2003)
• Biomedical studies of bones and teeth
• Art restoration (or conservation), by analyzing
  pigments and/or precious and ancient metals
  (Anzano et al., 2002)

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LIBS for coin compositional determination
Experimental set-up
Movie
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With a Photo-Diode Array (PDA), one can
simultaneously detect the intensity of many
different wavelengths.
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LIBS for coin compositional determination
Experimental Results

• PDA Calibration
• Apply LIBS to coins
• Check repeatability
• Look for coin signatures
• Reliability (same results in different regions!!)
• NDT

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LIBS for coin compositional determination
Fe I 4045.8 4000
Fe I 4063.6 1500
Fe I 4071.7 1200
Fe I 4143.9 800
Br II 4223.9 1000
Fe I 4260.5 800
Fe I 4271.8 1200
Fe I 4282.4 1200
Fe I 4307.9 1200
Fe I 4325.8 1500
Br I 4365.1 2000
Br II 4365.6 1000
Fe I 4375.9 800
Fe I 4383.5 3000
Fe I 4404.8 1200
Br I 4425.1 1500
10 iron in KBr (calibration pellet)
http//physics.nist.gov/cgi-bin/AtData/lines_form
Data 4000-4400 Å
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LIBS spectra for (solid) one side of a 25 Fils
Bahrain coin and (dashed) the other side of the
same coin.
Notice how the spectra are almost identical!!
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There are similarities between the three spectra
for example, all have Fe peaks (e.g., _at_ 4228 Å.
The game token does not contain copper (e.g. _at_
4180, 4275 4377 Å). The real currencies do
contain copper!!
LIBS spectra for (solid) a 10-Hallalah Saudi
coin, (dashed) 20 cent Euro coin and (dotted) a
game token, in the 4000-4425 Å region.
The game token has more iron and nickel than the
other (real) currencies.
The Euro coin does not have the 4201 4401Å Ni
peaks.
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Common iron peaks (e.g. 5270 Å).
The game token does not contain copper. The real
currencies do contain copper!! (e.g. 5293 Å).
The Euro coin does not have the Ni peaks. (e.g.
5475 Å).
LIBS spectra for (solid) a 10-Hallalah Saudi
coin, (dashed) 20 cent Euro coin and (dotted) a
game token, in the 5250-5550 Å region.
The results are consistent with that of the
4000-4400 Å region.
It is difficult to distinguish between Saudi and
Bahrani coins. They probably have very similar
elemental composition.
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(a)
(b)
Photographs of the four coins used in the
experiments (a) before and (b) after 30 seconds
of laser irradiation. The coins show no apparent
destruction due to LIBS.
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LIBS as NDT?
Is LIBS absolutely NDT?
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LIBS for coin compositional determination
Conclusions

• LIBS spectra are repeatable.
• LIBS gives consistent/ reliable results in
  different regions.
• Coins have iron.
• Game token has no copper.
• 20 cent Euro coin is nickel-free.
• We can distinguish between different
  currencies using LIBS.
• The spectra of the Saudi 10-Hallalah and the
  Bahrain 25 Fils are very similar.
• At the macroscopic level, LIBS procedure can be
  NDT.

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Good general references on LIBS
Also, check Applied Optics vol 42 (30), Oct. 2003
(theme issue)
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Concluding Remarks

1. LIBS is a very useful technique for the elemental
   analysis of material.
2. LIBS can be used for fast, precise, on-line,
   non-destructive testing of coins.
3. LIBS can be beneficial for the identification of
   currency and also for quality control in coins
   production.
4. LIBS applies to different types of material and
   is conducive to interdisciplinary research, a
   concept very beneficial for academic research in
   Saudi Arabia.

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• Further study
• both qualitative and quantitative.
• different photon energy and laser pulse energy.
• effect of optical alignment of beam with the
  sample, and optical alignment of beam with the
  detection system.
• increase sensitivity by using gated ICCD.
• study the effects of delayed time.
• I would be happy to work with collaborators.

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Acknowledgement
The support of King Fahd University of Petroleum
and Minerals is gratefully acknowledged. The
encouragement of professor M.A. Gondal, as well
as the assistance of Mr. Abdullah Baziyad and Mr.
Abdullah Al-Zahrani, is deeply appreciated. I am
thankful to Mr. Fuad Enaya for his help in
preparing the presentation.
Thank you for your attention
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Complications in Using LIBS
Sample matrix Morphology Power energy per pulse
pulse width dependence Atmosphere type and
pressure Shot to shot energy fluctuation Depends
on photon energy esp. plasma absorption