Triple NIR light excited up‐conversion luminescence in lanthanide‐doped BaTiO3 phosphors for anti‐counterfeiting

Abstract

AbstractUp‐conversion luminescent (UCL) materials are excellent candidate for optical anti‐counterfeiting and the exploitation of multi‐wavelength NIR light triggered UC phosphors with tunable color emission is essential for reliable anti‐counterfeiting technology. Herein, a series of lanthanide ions (Er3+, Er3+–Ho3+, and Yb3+–Tm3+) doped BaTiO3 submicrometer particles are synthesized through a modified hydrothermal procedure. XRD and SEM measurements were carried out to identify the structure and morphology of the samples and their UCL properties under 808, 980, and 1550 nm NIR excitation are investigated. Er3+ singly doped sample exhibits Er3+ concentration‐dependent and excitation wavelength‐dependent emission color from green to yellow and orange. The corresponding UC mechanisms under three NIR light excitation are clarified. Pure red emission under 1550‐nm excitation was obtained by introducing small amount of Ho3+ and the fluorescent lifetime test was used to confirm the energy transfer from Er3+ to Ho3+. In addition, Yb3+–Tm3+ co‐doped sample shows intense blue emission from 1G4 → 3H6 transition of Tm3+ under 980‐nm excitation. As a proof of concept, the designed pattern using phosphors with red, green, and blue three primary color emissions under 1550, 808, and 980 nm NIR excitation was displayed to demonstrate their anti‐counterfeiting application.