Multifunctional lanthanide ions‐doped Ba2TiGe2O8 phosphor for near-infrared ratiometric thermometer and information security

On the basis of the remarkable optical properties, lanthanide ions‐doped luminescent materials have recently received increasing attention in the fields of information security and temperature sensors. Herein, the Ba2TiGe2O8 (BTGO) matrix can realize the cyan self-activated photoluminescence, the colour of lanthanide ions (Eu3+, Tb3+, Pr3+) doped BTGO phosphors can also change from cyan to red, green and yellow with varying excitation wavelength. Therefore, the dots with the various colour are designed to denote specific information for recognizing hiding message. In addition, a nonintrusive near-infrared (NIR)-II/III optical thermometer based on BTGO: Yb3+/Ho3+/Er3+ phosphor is also developed utilizing the phonon-assisted downshifting emissions (Ho3+, Er3+). All the results indicate that the optical property of lanthanide ions-doped BTGO phosphors are an important research and application field in the ratio thermometer and information security.