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www.reading.ac.uk
Emily Sonnex
Identification of forged Bank of England £20 banknotes using IR spectroscopy
Infrared spectroscopy in ForensicsFT-IR has been used for many forensic applications
Infrared microscopy is a relatively new technique and currently has few forensic uses
Perkin Elmer Spectrum 100 with Spotlight 400 imaging system attachment (Beaconsfield, UK)
Figure 1. Perkin Elmer Spectrum 100 and Spotlight 400 FT-IR
Banknotes -Previous workVila et al. (2006), used ATR FT-IR to distinguish between
forged and genuine euro notes
Distinct differences in spectra between the notes
Little other work has been done in this field
Is it possible to do the same with notes from the Bank of England and develop a method for their identification?
Vila et al. Analytica Chemica Acta 559 (2006) 257-263
FT-IR of banknotes
ATR attachment on a spectrum 100
Additional peaks in the forged notes
Calcium carbonate
1400 cm-1 broad, stretching mode
879 and 715 cm-1 sharp, deformation mode
Figure 2. FT-IR spectra of genuine (top) and forged (bottom) notes, paper area
Simplifying the process
Nicolet IR 100 FT-IR by Fisher Scientific ‘spectrometer in a suitcase’
Identifying peak at 1400 cm-1 still present.
Figure 3. FT-IR spectra of genuine (top) and forged (bottom) notes, paper area
Investigating other areas of the note
The hologram section was also investigated
Several subtle differences observed
υ(OH) ~ 3500 cm-1
υ(C-H) ~ 2900 cm-1
υ(C=O) ~ 1740cm-1
Requires greater skill to identify differences in these peaks
Figure 4. FT-IR spectra of genuine (top) and forged (bottom) notes, hologram area
Taking it further
Spectrum 100 FT-IR with Spotlight 400 microscope attachment
Spectral imaging with principle component analysis
Mirrors the work of Villa et al.
Figure 5. Visible image and spectral map of a banknote with corresponding spectra, Forged (left) and Genuine (right)
Looking forward
The Bank of England has announced its intent to issue polymer banknotes from 2016
Australia is currently a large producer of polymer banknotes
Most of their detectable forged notes are printed on paper
Could the proposed method be extended to polymer notes even if the forgeries were printed on polymer?
FT-IR of polymer banknotes
The polymer notes can be distinguished from other readily available polymers
-Acetate
-PolyethyleneFigure 6. FT-IR spectra to compare genuine Australian banknote (top) Cellulose acetate (middle) Polyethylene (bottom)
Spectral mapping of polymer banknotes
Spectral maps of polymer banknotes were recorded
No spectral contrast seen other than black writing
May see a contrast if forged notes were produced on polymer
Figure 8. Visible image and spectral maps of an Australian banknote , Main body (left) and Black writing (right)
FT-IR of polymer banknotes
The polymer notes have two distinct sections – a clear window and the rest of the note
Both are distinctly different to forged paper notes Figure 9. FT-IR spectra to compare forged banknote (top) Australian
banknote printed section (middle) Australian banknote clear window (bottom)