Waterborne polyurethane/YVO4:Eu3+ nanocomposites for UV-responsive anti-counterfeiting ink

In recent years, there has been a growing demand for advanced materials with security and anti-counterfeiting functionalities, particularly for applications in security printing and smart labeling. In this study, luminescent nanocomposites were successfully synthesized by dispersing Eu 3+ rare earth ion-doped YVO 4 nanoparticles (YVO 4 :Eu 3+ NPs) at an optimized concentration into a waterborne polyurethane (WPU) polymer matrix. The YVO 4 :Eu 3+ NPs were synthesized using the co-precipitation method, yielding highly crystalline nanostructures, as confirmed by X-ray diffraction analysis. Field emission scanning electron microscopy revealed nearly spherical YVO 4 :Eu 3+ NPs with an average diameter in the range of 31–37 nm, which is well suited for inkjet printing applications. Photoluminescence (PL) characterization demonstrated that doping with 5 mol% Eu 3+ resulted in the maximum emission intensity. The YVO 4 :Eu 3+ NPs were uniformly dispersed in the WPU matrix without noticeable agglomeration or structural degradation. The nanocomposite was used as a luminescent ink for printing labels using both screen printing and electrohydrodynamic inkjet printing techniques. The printed patterns exhibited sharp, seamless lines with widths of 130-250 μm and emitted red luminescence under UV irradiation. The combination of luminescent NPs with a flexible WPU matrix opens up the possibility of applications in security labels, anti-counterfeiting coatings, and flexible luminescent devices.