Lanthanides-based luminescent hydrogels applied as luminescent inks for anti-counterfeiting

Lanthanides-based luminescent hydrogels emitting green and red luminescence have been fabricated successfully by the coordinative self-assembly of 1,3,5-benzenetricarboxylic acid (H3BTC) and lanthanide ions (Tb3+ or Eu3+). And the hydrogel with yellow emission color can be obtained by controlling the molar ratio of Tb3+ to Eu3+ at 9/1. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the formation of coordination bonds between H3BTC and lanthanides. Scanning electron microscopy images showed that the hydrogels formed 3D porous structures. Luminescent spectra, luminescent decay curves, and digital images indicated that the H3BTC-lanthanides hydrogels can be applied as luminescent inks for anti-counterfeiting. Importantly, the rational designed multiple encryption strategies were applied for improving the anti-counterfeiting level. This work provides an alternative strategy to prepare lanthanides-based luminescent materials for anti-counterfeiting.