Three techniques - X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and scanning electron microscopy (SEM) - were used to analyze the elemental composition of two European coins without damaging them. XPS and UPS identified the elements in each coin by the binding energies of ejected electrons. SEM further verified the identified elements and provided information on their relative concentrations in different areas of the coins. The analyses found that the British penny was mostly copper, while the Euro coin's center was a copper-nickel alloy and its outer ring was a copper-zinc alloy, consistent with reported compositions.

1. Elemental Analysis of European Coins Using Photoelectric Spectroscopy
N. Turpin, W. Chen, M. Mezher, D. Hanks
Department of Chemistry, University of Nevada, Las Vegas
Introduction
New techniques were employed to determine the make up of
two different types of European coins that are worth more
than the US Dollar (according to current exchange rates) to
ensure the integrity of each. These new techniques, XPS,
UPS, and SEM, were able to analyze each coin without
defacing the legal tender. Each element in the sample could
be identified by its corresponding, ejected electron.
Databases have been compiled extensively with data for
these types of spectroscopy.(4) The experimental findings
were compared with the reported make up of each coin.
Methods and Materials
http://photonicswiki.org/index.php?title=Photoelectron_Spectrometer_X
PS_and_UPS
Key points to understand for this experiment:
*X-ray Photoelectric Spectroscopy sends photon in and a core electron
comes out.
*UV Photoelectric Spectroscopy sends a photon in and a valence
electron comes out.
*Scanning Electron Microscope sends a focused beam of electrons onto
surface of sample, detects back-scattered and secondary electrons along
with x-rays.
These detected and measured electrons were identified to their host atom
by their binding energy confirmed by references.
The instrument used for the XPS and UPS was an amalgam of
components from different manufactures. Such components included,
but not limited to: Specs XR 50 X-ray source, VG Scienta R4000
spectrometer, Stanford Research Systems residual gas analyzer 300. Due
to the mixed family of devices from different manufacturers this device
was wittily referred to as “The Brady Bunch.” Thus reaffirming the
“indisputable truth that PHYSICAL CHEMISTRY IS FUN.” (2) The
SEM used was a Joel JSM-5600.
References
[1] European Central Bank. https://www.ecb.europa.eu/euro/coins/1euro/html/index.en.html (accessed Oct 29, 2014).
[2] Mezher, M., Hanks, J. CHEM 423L Syllabus, Chem. Dept. UNLV, 2014.
[3] Moulder, J.F., et al. Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer: Eden Prairie, 1992
[4] National Institute of Standards and Technology. NIST X-ray Photoelectron Spectroscopy Database;
http://srdata.nist.gov/xps/Default.aspx, (accessed Oct 29, 2014).
[5] The Royal Mint. http://www.royalmintmuseum.org.uk/coins/british-coinage/current-coins/one-penny-coin/index.html (accessed Oct
29, 2014)
Data
British Penny 1 € National Coin
Goal: To determine the elemental make up of each coin.
British Penny 1st Sweep with Al Kα
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
100.00
250.00
400.00
550.00
700.00
850.00
1000.00
1150.00
1300.00
1450.00
Binding Energy
CountsPerSecond
O 1s
Cu Auger
L3M45M45
Satellite
Satellite
Cu 2p1/2
O Auger
KL1L1
C 1s
Euro XPS
0
20000
40000
60000
80000
100000
120000
140000
160000
100.0
250.0
400.0
550.0
700.0
850.0
1000.0
1150.0
1300.0
1450.0
KE (eV)
CountsperSecond
SEM Surface Img
XPS
SEM
XPS
SEM
SEM Surface Image
Inner part / Outer ring
Results
Both coins were cleaned by
sonication in acetone. The 1€
had to be trimmed in order to
fit into the holder for XPS. It
was cut with a silicon carbide
blade but not cleaned properly.
As a result, peaks for silicon
and carbon in the form of
carbide were detected.
XPS was performed with non-
monochromated x-ray. This
was why many unidentifiable
peaks were present in spectra.
UPS was performed with
monochromated UV light from
excited He. The advantage of
UPS was that it was more
surface-sensitive, thus
produced narrower line peaks.
SEM confirmed the identified
peaks from the XPS/UPS
spectra. Relative
concentrations of elements
were identified as well by the
SEM. The British Penny was
coated with mostly copper and
a little of oxygen from the
oxide form of the copper. The
Euro’s center was 67:31:2 Cu-
Ni-Zn alloy. Its outer ring
consisted of 67:22:11 Cu-Zn-
Ni alloy. The actual
composition of the coin was
not listed. Simply stated:
copper-nickel alloy for the
center and copper-zinc alloy
for the ring (1).
Discussion
Photoelectric spectroscopy was a useful tool for verifying the contents of
the two coins. XPS did a good job at identifying the elements on the
surface (3,4). This included contaminants such as NaCl from sweaty
fingers and SiC from the cutting disc used on the Euro. Satellite and
shake off peaks in the XPS spectrum made it somewhat confusing for the
identification. The NIST database(4) proved especially useful for peak
identification. A much better spectrum could have been obtained had a
monochromated x-ray source been used. Due to time limitations that was
skipped and SEM was used to verify elements. UPS was not used fully in
this experiment. UPS did verify the presence of copper with the lone
“bump” in the spectrum.
SEM was the most user-friendly. The beam was easily focused on
specific locations of the coins in order to analyze the specific location.
SiC was verified using SEM but omitted form the images because of the
delocalization of the contaminant.
All in all, these two currencies proved valid and legit based on the
published information from both mints.
C 1s
O 1s
Cl Alkali
Si 2s
Cu
2p3/2
Cu 2s
Cu
2p1/2
Ni 2p3/2
Ni 3p
Zn
2p3/2
British Penny UPS
0.00E+00
2.00E+04
4.00E+04
6.00E+04
8.00E+04
1.00E+05
1.20E+05
1.40E+05
-34.8 -32.3 -29.8 -27.3 -24.8 -22.3 -19.8 -17.3 -14.8 -12.3 -9.8 -7.3 -4.8 -2.3
Kinetic Energy (eV)
CountsperSecond
UPS
(5)
(1)