Luminescent Poly(vinylidene fluoride)‐Based Inks for Anticounterfeiting Applications

Abstract

Counterfeiting is a global ever-growing problem of immense magnitude that represents a menace to security, economy, and health at a worldwide level. Herein, a new luminescent security ink composed of poly(vinylidene fluoride) (PVDF) and the home-made ionic liquid (IL) 1-butyl-3-methylimidazolium tetra(thenoyltrifluoroacetonato)europate(III) ([Bmim][Eu(tta)4]) is reported. The optimized PVDF/[Bmim][Eu(tta)4] composite is processed by the doctor blade method as a micrometer-thick film invisible under white light, with porous texture. The material exhibits high thermal stability, high chemical stability (inertness with respect to ethanol), high photostability, and intense red emission when excited with long UV radiation (365?nm) with a maximum quantum yield value of 0.10?±?0.01. A test of the PVDF/[Bmim][Eu(tta)4] ink screen-printed on a medical N95 protection mask performed under irradiation with white light and with a commercial 365?nm LED demonstrates its suitability to combat fraud. The exciting possibilities offered by PVDF/luminescent IL pair in terms of chemical modification of PVDF (copolymerization or functionalization) and IL (cation type/lanthanide ion/ligand type) for the tuning of the ink properties allow envisaging the production of tailor-made tri- or biluminescent security inks, for authentication purposes.