Counterfeiting money has existed for as long as money has been in use. However, gone are the days of shaving coins or engraving a printing press, as modern technologies like digital printing and graphic arts have made it easier to forge items like banknotes and important documents. Therefore, features based on molecular properties that can be verified in a short space of time are integral to increasing the security needed to easily identify counterfeit materials.
Luminescence is one such molecular property that is being used in the modern fabrication of documents and banknotes. Luminescent materials can absorb energy and then emit that energy as a photon of light which can be observed either as a visual readout or checked spectroscopically. Formulation of luminescent composite materials is a challenge in the security industry, banknote fabrication in particular, consists of multiple chemical processes to embed security features. The solubility of novel luminescent complexes and material stability are two components that can make or break a new compound going to market.
This project involves the synthesis, characterisation and composite formulation of novel luminescent ionic liquids that inherently overcome these issues. Ionic liquids being a class of materials that exist as a liquid but only consist of a positively charged species (cation) and a negatively charged species (anion) without the need for a solvent. These functional liquids can then be mixed with ease to form novel photo responsive materials. The project will involve fabrication of ionic liquid composite materials based on lanthanide coordination complexes, to cover both the visible and near infrared emission wavelengths, for use in security inks aimed at application in banknotes, food security and raw materials labelling. The physical state properties of the newly developed ionic liquids such as melting/glass temperature, and conductivity will also be explored as these can add an extra layer of difficulty in counterfeit reproduction of the security materials.
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