Preparation of fluorescent ink using perylene-encapsulated silica nanoparticles toward authentication of documents

Novel inorganic–organic hybrid fluorescent ink was produced for anticounterfeiting applications. Pigment/resin ink formulations were prepared from the thermally and photostable fluorescent perylene-doped silica nanoparticles (PSN). To create a colorless printed film from pigment/resin ink, the fluorescent perylene must be physically disseminated without clumping. Using screen-printing technique, the pigment/resin combination was successfully applied to sheets of cellulose paper. CIE Lab tests showed that pigment concentrations as low as 1 % result in a red emission when a uniform fluorescent layer was produced on the pale yellow cellulose paper surface. These printed sheets displayed an absorption band at 436 nm and an emission band at 625 nm. The fluorescent PSN exhibited diameters of 6–33 nm. The printed paper sheet was analyzed using various spectroscopic techniques, including scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), energy-dispersive X-ray (EDX), and wavelength dispersive X-ray fluorescence (WDXRF). Upon repeated exposure to UV light, the prints exhibited a reversible fluorescence. Investigations into the ink rheological characteristics, stability, and printability were conducted.