Multiple Anti-Counterfeiting and optical storage of reversible dual-mode luminescence modification in photochromic CaWO4: Yb3+, Er3+, Bi3+ phosphor

Luminescence modification of rare earth ions doped phosphors based on photochromism is beneficial to expand their practical applications. Here, Bi3+ co-doping CaWO4: Yb3+, Er3+ phosphor is prepared. Color of CaWO4: Yb3+, Er3+, Bi3+ phosphor turn black grey upon the 254 nm ultraviolet light irradiation due to Bi3+ co-doping induced formation of the defects. Black grey CaWO4: Yb3+, Er3+, Bi3+ phosphor can recover their color to the primitive state under the stimulation of 473 or 532 nm lasers, exhibiting the double-light induced reversible photochromism. Dual-mode upconversion and downshift luminescence of CaWO4: Yb3+, Er3+, Bi3+ phosphor is reversibly modified based on its photochromism property. Potential applications of CaWO4: Yb3+, Er3+, Bi3+ phosphor are explored. The CaWO4: Yb3+, Er3+, Bi3+ phosphor is formulated into the inks, printed on the flexible substrate by the screen-printing technology. The luminescence color of printed various patterns can be changed based on the dual-mode luminescence modification, which demonstrate that the CaWO4: Yb3+, Er3+, Bi3+ phosphor ink is an ideal multiple anti-counterfeiting agent. The optical information recorded on the binary photochromic dot arrays of CaWO4: Yb3+, Er3+, Bi3+ sheet could be read upon the UV and near infrared light excitation, exhibiting the potential application of CaWO4: Yb3+, Er3+, Bi3+ phosphor as optical data storage medium.