Functional inks for smart label design

Based on its expertise in nanochemistry, the PRINTUP institute develops customized inks for several applications such as health and environment. Recently, we have developed an innovative grafting method on Ag nanoparticles allowing us the introduction of a wide range of functions on their surface. We have illustrated the potential of this methodology by producing inks with controlled and intense Raman signatures. Such inks have attracted great interest in recent years for their use as security labels in anti-counterfeiting applications. Indeed, they are promising alternatives to luminescent inks, which suffer from several limitations including emission peak overlap, toxicity and photobleaching. To overcome this issue, we develop a new generation of security labels based on silver nanoparticles (Ag NPs) functionalized by aryl diazonium salts, carrying various substituents (–NO2, –CN, –CCH) with distinguishable Raman fingerprints. The resulting tags were fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption and SERS. Then, they were incorporated into ink formulations to be printed on polyethylene naphthalate (PEN) substrates, using handwriting or inkjet printing.