Skenderović Božičević, Martina (2016) Primjena Ramanske spektroskopije i energetsko disperzivne fluorescencije rendgenskih zraka u forenzičnoj analizi krivotvorenih novčanica = Application of raman spectroscopy and energy dispersive x ray fluorescence in the forensic examination of counterfeit banknotes. Dissertation (PhD) thesis. Grafički fakultet. [Mentor: Zjakić, Igor].
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Abstract
U postupku analize krivotvorenih novčanica kao osnovne metode vještačenja danas se koriste vizualne metode analize. Takva vizualna analiza u pojedinim slučajevima dovodi do zaključka da krivotvoreni primjerci potječu iz istog 'izvora' što zapravo podrazumijeva da ih je izradio isti krivotvoritelj ili povezana skupina krivotvoritelja. Međutim, postoje slučajevi u kojima navedene vizualne metode nisu dostatne te je stoga u postupak analize krivotvorenih novčanica nužno implementirati znanstveno potkrijepljene i dokazano primjenjive metode za analizu papira i primijenjenih tehnika reprodukcije te njihovu usporedbu. Svrha ovog istraživanja jest istražiti potencijal primjene mikro-Ramanove spektroskopije i energetsko disperzivne fluorescencije rendgenskih zraka (engl. Energy Dispersive X-Ray Fluorescence; EDXRF) kao nedestruktivnih metoda analize krivotvorenih novčanica izrađenih na papirnim podlogama ispisom tonerom, inkjet tintom ili ofset-tiskom. Cilj istraživanja jest dokazati da su mikro-Ramanova spektroskopija i EDXRF metoda uspješno primjenjive u analizi krivotvorenih novčanica. Svrha ovog istraživanja jest unapređenje postupka vještačenja krivotvorenih novčanica implementacijom znanstveno utemeljenih metoda analize. Sukladno tome izabrani su uzorci koji odgovaraju najčešćim stvarnim uvjetima analize krivotvorenih novčanica neovisno o valuti i imitiranoj nominalnoj vrijednosti. Snimanja svih uzoraka provedena su na način da je obavljena izdvojena analiza elemenata reprodukcije u plavozelenoj, purpurnoj, žutoj i crnoj boji. Zaključeno je da pojedini papiri posjeduju karakteristične ramanske spektre čije vrpce se opažaju u ramanskim spektrima inkjet tinte, tonera ili ofsetnog tiskarskog bojila, snimljenim direktno na tim papirima bez prethodne pripreme. Ovom metodom moguće je zasebno analizirati ramanski spektar tonera, inkjet tinte ili ofsetnog tiskarskog bojila te ih uspoređivati s ramanskim spektrima drugih tonera, inkjet tinti i ofsetnih tiskarskih bojila koji su obrađeni na isti način, bez obzira na karakteristike papira na kojima su ispisani. Pobudno zračenje od 784.3 nm učinkovitije je u svrhu diskriminacije uzoraka kako ofsetnih tako i uredskih papira, od pobudnog zračenja od 514.5 nm. Pobudnim zračenjem od 514.5 nm moguća je međusobna diskriminacija tonera, inkjet tinti i ofsetnih tiskarskih bojila. EDXRF metodom mjereni su kemijski elementi u uzorcima različitih papira i procesnih boja te je moguća analiza i diskriminacija različitih vrsta papira. Usporedba plavozelenih tonera, inkjet tinti i ofsetnih bojila kao i crnih inkjet tinti mogla bi biti moguća jedino na osnovu analize količine bakra u pojedinim uzorcima.
| Item Type: | Dissertation (PhD) thesis |
|---|---|
| Mentor name: | Zjakić, Igor |
| Other mentors: | Gajović, Andreja |
| Thesis Committee: | Mrvac, Nikola and Mikota, Miroslav and Modrić, Damir and Žiljak Stanimirović, Ivana and Obhođaš, Jasmina and Poljičak, Ante and Glogar, Martinia Ira |
| Defence date: | 10 February 2016 |
| Abstract in english: | Usual methodology of counterfeit banknote analysis comprises optical methods of examination under the visible, ultraviolet and infrared electromagnetic spectrum. These methods serve to collect as much as possible information about the paper, toner, inkjet ink, ofset ink, security features' imitations and identification of the reproduction techniques. The same methods are used for the comparative analysis of the two or more samples of counterfeit banknotes on which basis the conclusion about the similarities and differences between them can be made. In some cases this kind of analysis leads to the conclusion that the source of the counterfeit samples is the same what implies that they were made by the same or organized group of counterfeiters. Most of the counterfeit banknotes, regardless of the currency, are offset printed followed by less numerous inkjet (or similar water based inks) and toner printed copies. Optical methods as the tool for determining the similarities or differences between two or more specimens of counterfeit banknotes in a comparative expert analysis are sufficient in most cases related to currency counterfeiting. Difficulties begin with counterfeit currency cases where different nominal values or currencies without the distinctive imitation of security features are made by the same perpetrator. There could be also the counterfeit banknotes cases where the imitation of security feature is distinctive but is easily available for use to different perpetrators and the printing technique and substrate of the counterfeited banknotes are more or less different. In both circumstances the expert cannot rely on the optical comparison of inks or paper only. The newest challenge for counterfeit banknote experts in currency counterfeiting criminal offences could be the sharing or selling of prepress data files electronically when the same reproduction of motives of original banknotes become available to different perpetrators, printing counterfeit banknotes on their own initiative, which probably implies the use of substrates and inks with different properties. In the counterfeiting cases of the same denomination and currency and even the same serial number when counterfeit banknotes appear identical at the first glance but detailed analysis of the optical characteristics and reproduction techniques implies possibility that they are coming from different sources, additional analytical techniques of paper and reproduction techniques are also needed in order to determine commonality or dissimilarity of two or more counterfeit samples. In all above mentioned hypothetical currency counterfeiting circumstances, additional methods of analysis of ink and paper and their comparison are crucially needed, besides already applied physical and optical analysis, in order to decide whether counterfeit banknotes are coming from the same source or not. Therefore, in addition to the existing optical methods of counterfeit banknote analysis it is necessary to implement scientifically based and proven workable methods for the analysis of paper and applied reproduction techniques and their comparison in the counterfeit banknote analysis methodology. In some cases such methods would only give scientific confirmation of the optical analysis results, and in the remaining cases would provide a proof of identity or difference between two or more counterfeit banknote samples, individually analyzed in a scientific manner, regardless of their visual similarity or dissimilarity. The result of such counterfeit banknote analysis methodology would have greater impact and credibility when presenting the expert opinions in judicial proceedings. Raman spectroscopy and Energy Dispersive X-ray Fluorescence (EDXRF) are analytical methods already applied, although not systematically, in the questioned document analysis. The purpose of the research conducted in the framework of this doctoral thesis is to explore the potential applications of micro-Raman spectroscopy and EDXRF as a non-destructive methods of analysis of counterfeit banknotes produced on paper substrates by toner, inkjet ink or offset printing. The research objective is to prove that the micro-Raman spectroscopy and EDXRF are successfully applicable in the counterfeit banknotes analysis. Raman spectroscopy was performed on the system Jobin Yvon T64000 with a monochromatic light source of 514.5 nm wavelength in the micro-Raman mode and Raman system Maya 2000 with a monochromatic light source of 784.3 nm wavelength. EDXRF technique was performed by Siemens's W X-ray tube and Canberra Si(Li) detector with a Mo secondary target in orthogonal geometry. The purpose of this research is the improvement of a counterfeit banknote analysis methodology through the implementation of science-based methods of analysis. Accordingly, selected specimens correspond to the most common real conditions of counterfeit banknotes analysis with regard to paper type and reproduction techniques and regardless of the currency and denomination. Twelve toner specimens, ten inkjet ink specimens and eighteen offset printing ink specimens are subjected to analysis. Measurements for all specimens were analyzed in such a way that a reproduction elements of each process colour, cyan, magenta, yellow and black, was analyzed separately. Keeping in mind the initial idea and the purpose of this research and the possibility of the final implementation of presented methods in the counterfeit banknote analysis, it should be noted that the main objective of the application of either Raman spectroscopy or EDXRF in the forensic analysis of counterfeited banknotes is to establish, confirm or refute the commonality or dissimilarity of two or more specimens of toner, inkjet ink, offset printing ink or paper. Therefore, the focus of interest of this research is not to determine the physical or chemical characteristics of the specimens but their interrelationship without taking into account their visual characteristics that could be studied by means of conventional methods of graphic reproduction and graphic materials analysis. When applying Raman spectroscopy with a monochromatic light source of 514.5 nm it was necessary to choose only one dot of a specific colour in order to make a micro-Raman measurement on approximately 1 square micrometer of the specimen. Comparisons of Raman spectra were conducted on the basis of the presence of characteristic Raman bands in a way that the Raman spectra are considered different if there is at least one difference in positions of Raman bands between the two Raman spectra. It was concluded that some papers have characteristic Raman spectrum that may affect the Raman spectrum of inkjet ink, toner or offset printing ink, measured directly on that paper. Therefore it is important to consider it in the application of Raman spectroscopy in the counterfeit banknotes or questioned documents forensic analysis. In cases where the Raman spectrum of paper really affects the measured Raman spectrum of a specimen, from the Raman spectrum of the specimen is necessary to take away the Raman spectrum of paper most often with an aid of the Raman spectroscopy system's software. Once the Raman spectrum of paper is cancelled by subtracting, it is possible to make an independent analysis of the Raman spectra of toner, inkjet ink or offset printing ink, and compare them with the Raman spectra of other toner, inkjet inks and offset printing inks which are prepared in the same way, regardless of characteristics of the paper on which they were printed on. Raman spectroscopy with a monochromatic light source of 784.3 nm is showed to be more effective in discrimination of paper specimens, than Raman spectroscopy with a monochromatic light source of 514.5 nm. Discrimination of office and offset paper specimens according to characteristic positions of the Raman bands is not related to their affiliation to a particular manufacturer. Raman spectroscopy with a monochromatic light source of 514.5 nm allows discrimination of yellow and magenta toners, while the discrimination of cyan toners is not possible due to identical positions of Raman bands. Measurement efficacy of cyan toner was 100%, yellow 83% and magenta 66%. Discrimination of toner specimens according to characteristic positions of the Raman bands is not related to their affiliation to a particular manufacturer. Raman spectroscopy with a monochromatic light source of 514.5 nm provides discrimination of yellow and cyan inkjet inks, while the measurement of magenta inkjet ink specimens was not successful. Measurement efficacy of cyan inkjet ink was 70% and yellow 80%. Discrimination of inkjet ink specimens according to characteristic positions of the Raman bands is not related to their affiliation to a particular manufacturer. Raman spectroscopy with a monochromatic light source of 514.5 nm did not provide discrimination of yellow and cyan offset inks, while the measurement of magenta offset ink specimens was not successful. Measurement efficacy of cyan offset ink was 94% and yellow 89%. The results of analysis of paper, toner, inkjet ink and offset ink specimens by micro-Raman spectroscopy showed that the method allows differentiation of different toners reproduced on different papers, different inkjet inks reproduced on different papers and different offset inks printed on different papers. A prerequisite of their discrimination is of course their different chemical composition. Measurement of chemical elements in the specimens of different papers and process colours reproduction elements was done by EDXRF technique. EDXRF analysis of 20 office and 20 offset papers on the basis of comparison of their Ca:Sr, Ca:Fe, Ca:Br and Ca:Ti ratios showed that papers of different chemical composition can be distinguished by this method. Further analysis of eighteen offset paper specimens and reproduction elements in cyan, magenta, yellow and black showed that offset papers can be distinguished among each other. Measured values were processed by BG-PCA statistical analysis. Analysis of the cyan, magenta, yellow and black reproduction elements showed that only cyan toner, inkjet and offset inks as well as black inkjet inks can be detected by this technique due to presence of copper (Cu) that can be a base for their comparison. The latter was not proved by this research because information on the chemical composition of the ink, toner or offset ink could not have been separated from the information on the chemical composition of the paper with the applied EDXRF technique. The findings that have arisen from the analysis of measurements done on the specimens in this study are applicable in forensic analysis of counterfeit banknotes with the purpose of identifying characteristic Raman spectra of paper, toner, inkjet ink or offset printing ink specimens, as well as the chemical composition of the paper. |
| Uncontrolled Keywords: | krivotvorina, toner, tinta, tiskarska boja, papir, Ramanova spektroskopija, EDXRF |
| Keywords in english: | counterfeit, toner, ink, offset ink, paper, Raman spectroscopy, EDXRF |
| Subjects: | TECHNICAL SCIENCES > Graphic Technology |
| Institution: | Grafički fakultet |
| City: | Zagreb |
| Number of Pages: | 107 |
| Callnumber: | 343.51 SKE p |
| Inventory number: | 10118 |
| Depositing User: | Nina Jelača |
| Status: | Unpublished |
| Date Deposited: | 24 Feb 2016 08:31 |
| Last Modified: | 24 Feb 2016 08:31 |
| URI: | http://eprints.grf.unizg.hr/id/eprint/2476 |
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