Dy3+, Mn4+ co-doped Sr4GaNbO8 materials towards dual-mode thermometry, anti-counterfeiting and information encryption applications

Herein, we reported a novel multi-function phosphor Sr4GaNbO8:Dy3+/Mn4+ with excellent performance. Under different UV excitations, the phosphor simultaneously exhibited characteristic emissions of Dy3+ around 490 and 578 nm and Mn4+ around 712 nm, realizing the tunable luminescence from yellow to red. Moreover, there is energy transfer between Mn4+ and Dy3+ in the co-doped phosphor. Based on the fluorescence intensity ratio (FIR) technique, maximum relative sensitivities (Sr) and absolute sensitivity (Sa) were achieved to be 14.12% K-1@298 K and 2.33 K-1@473K for Sr4GaNbO8:0.04Dy3+ ,0.005Mn4+, and 13.92% K-1@298 K and 1.68 K-1@473K, respectively, and for Sr4GaNbO8:0.04Dy3+,0.007Mn4+, which were much higher
than most reported results. Remarkably, we proposed an innovative fluorescence lifetime ratio (FLR) prototype approach based on the opposite change of temperature-dependent lifetime behaviors for Dy3+ and Mn4+ under 285 nm excitation, achieving maximal Sr and Sa values of 34.08% K-1@298 K and 5.22 K -1@393 K for the Sr4GaNbO8:0.04Dy3+,0.005Mn4+ sample, which is higher than those obtained using FIR technology, demonstrating its high potential in future design of fluorescent thermometers with higher sensitivity. Moreover, an anti-counterfeiting and information encryption model was designed based on the tunable luminescence properties related to excitation wavelength (250 - 420 nm) and temperature (298 - 473 K) of as-prepared materials. The results enable breakthrough applications in optical sensing, optical encryption and dynamic anti-counterfeiting systems, providing innovative solutions for non-contact thermometry and information security.