Novel Application of Some Luminescent Materials for Anti-counterfeiting Purposes

Abstract

Counterfeiting of valuable paper documents is a serious issue that represents a major economic threat for many countries. Therefore, protecting valuable paper documents against counterfeiting is a vital national security task. The current thesis presents three new methods to solve this problem. The first method proposes the addition of calcium titanate impregnated with trace Praseodymium (CaTiO3-Pr(III), CTPr) as a luminescent tag during manufacturing of security paper, that provides a simple, non-destructive and effective solution. The structure and properties of the synthesized CTPr were explored using X-ray diffraction, scanning electron microscopy and photoluminescent analysis. The addition of CTPr improved the optical and mechanical properties of the prepared paper sheets. Under UV light of 365 nm, white papers containing (CaCO3, CaTiO3 and CaTiO3- Pr(III)) exhibited (pale blue, blue and red-violet) luminescent colors, respectively. The red-violet emission of Pr(III) under UV excitation is attributed to the 1D2 to 3H4 transition. Thus, papers secured with CTPr can be easily distinguished using a UV lamp as a fast, and easy way to protect important documents from fraud.