The present invention provides a secured document including a composition
capable of anti-Stokes fluorescence containing an ion capable of
absorption of electromagnetic radiation, an ion capable of emitting
electromagnetic radiation, and a matrix composition comprising gadolinium,
yttrium, lanthanum, and lutetium, wherein the wavelength of the emitted
electromagnetic radiation is shorter than the wavelength of the absorbed
electromagnetic radiation, and wherein the concentrations of the absorbing
and emitting ions are adjusted to achieve concentration quenching of
anti-Stokes luminescence.
