New insight into printable europium-doped yttrium borate luminescent pigment for security ink applications

Counterfeiting is a major current concern throughout the world, and recent technological advances have made counterfeiting of sophisticated products easy. It is therefore essential to develop further means to combat counterfeiting, including the use of new luminescent materials for security inks. Here, we report the synthesis by a sol–gel technique of a highly luminescent YBO₃:Eu³⁺ phosphor, which can be scaled up to 1 kg amounts in single batches. This phosphor is both structurally and chemically stable and has a particle size of 110 ± 10 nm. It emits strongly at a wavelength of 591 nm (orange–red) upon excitation at a wavelength of 245 nm and is also excitable by wavelengths in the 280–480 nm range. The structural and microstructural characteristics and the photoluminescence behavior of the phosphor were characterized by SEM, TEM/HRTEM, and fluorescent spectroscopy, respectively. The phosphor was used with a commercially available PVC gold medium to produce a luminescent security ink for printing security codes, and the results were investigated by photoluminescence mapping instruments. TheYBO₃: Eu³⁺ phosphor-based security ink described here provides a low-cost material for use in printing security codes that are easy to detect but difficult to counterfeit.