Thermo-enhanced afterglow emission in Tm3+ doped fluoride nanoparticles for anti-counterfeiting application after X-ray excitation

Multimodal luminescence has emerged as a promising solution in the realm of anti-counterfeiting techniques, which have gained global attention due to their association with information and data security. The conventional approach to achieving multimodal luminescence typically involves combining upconversion and downshifting luminescence, which necessitates the use of external excitation sources and costly detection equipment. Herein, we develop an anti-counterfeiting strategy based on the afterglow performance of NaLuF4: Gd, Tm nanoparticles after X-ray excitation. The X-ray-induced Frenkel defects-base traps ensnare electrons with low kinetic energy, resulting in the creation of persistent photon traps that are responsible for the temperature-dependent afterglow intensity. The dual-band and thermo-enhanced afterglow emission can encrypt information well according to our proof-of-concept experiment and the visible light signal can be successfully captured by a smartphone camera. These unique features of NaLuF4: Gd, Tm nanoparticles render them highly appealing for multilevel anti-counterfeiting applications.