An advanced color tunable persistent luminescent NaCa₂GeO₄F:Tb³⁺phosphor for multicolor anti-counterfeiting

Abstract

Luminescent materials play an important role in anticounterfeiting application due to their superior properties of visual convenience and high concealment. However, traditional luminescent materials usually exhibit monochromatic emission and are...

Tailored Luminescence Output of Bi3+-Doped BaGa2O4 Phosphors with the Assistance of the Introduction of Sr2+ Ions as Secondary Cations

“…The establishment of an energy transfer process, − modulation of the host matrix, development of new, efficient, and stable phosphors, − along with the exploration of WLED structures, , are continuously devoted to achieve improved luminescence performance of corresponding phosphors and advanced lighting and display devices. Moreover, persistent energy transfer, , controlled traps associated with tailoring of the trap density, and tuning of trap depth distributions , enable versatile application of optical storage materials for multicolor anti-counterfeiting, optical information storage, and autofluorescence-free optical imaging technology . Recently, Li et al proposed a conceptual trap energy upconversion, such as the rejuvenateable persistent luminescence from near-infrared to near-infrared light, which should provide a new viewpoint for the design of new persistent-luminescence materials for numerous photonic and biophotonic applications .…”

Lattice-site engineering in ZnGa2O4:Cr3+ through Li+ doping for dynamic luminescence and advanced optical anti-counterfeiting

“…The excitation spectra of ZGCL (x = 0-0.08) phosphors (PLE, Fig. 4a), recorded by monitoring the B695 nm near-infrared emission of Cr 3+ , present a broad and strong band ranging from B220 to 300 nm in each case, which is attributed to the overlap of band-gap transition (VB -CB) and 4 A 2 ( 4 F) -4 T 1 ( 4 P) transition of Cr 3+ . Meanwhile, the bands centered at B410 nm and B560 nm can be assigned to the 4 A 2 ( 4 F) -4 T 1 ( 4 F) and 4 A 2 ( 4 F) -4 T 2 ( 4 F) transitions of Cr 3+ .…”

“…4e and f including CB (conduction band), VB (valence band), and the energy levels of V o , Cr 3+ was constructed, which helped understand the electron transitions, energy transfer process and luminescence mechanism of the ZGCL phosphor. Under ultraviolet excitation, the electrons of Cr 3+ ion are excited from the ground state 4 A 2 to the excited state 4 T 1 ( 4 P), 4 T 1 ( 4 F), 4 T 2 ( 4 F), they then relax to the lowest excited state 2 E through a nonradiative transition, and then returned to the ground state 4 A 2 , thus producing NIR emission at 695 nm. 27,39 Meanwhile, the electrons excited to the conduction band and V o release first to the extended V o state by a nonradiative transition and then return to the valence band, resulting in a green-yellow emission.…”

“…By contrast, TM and RE-doped phosphors are considered to be competitive alternatives due to their advantages of good photochemical stability, adjustable color, and long afterglow, etc. 4 The potential strategies to increase the security of luminescent labels are based on the ability of the security images to be invisible under standard conditions but revealed under the appropriate illumination. Recently, a few phosphors, including LiLuF 4 /LiYF 4 doped with Eu 3+ /Ce 3+ , Tb 3+ / Ce 3+ , Er 3+ /Ho 3+ /Tm 3+ /Yb 3+ , 19 NaYF 4 doped with Er 3+ /Yb 3+ , Tm 3+ / Yb 3+ /Er 3+ , 20 LiNbO 3 :Pr 3+ , Tm 3+ , Er 3+ Yb 3+ , 21 and Eu 2+ , Er 3+ -doped La 4 GeO 8 3 were synthesized for anti-counterfeiting applications, and dynamic luminescence and different emitting images were obtained by varying the excitation wavelength.…”

A single-beam NIR laser-triggered full-color upconversion tuning of a Er/Tm:CsYb2F7@glass photothermal nanocomposite for optical security

“…Recently, some Ln-doped luminescent materials, such as Tb:NaCa 2 GeO 4 F, (Pr, Tm, Er, Yb):LiNbO 3 and (Yb/Er, Yb/ Tm):NaYF 4 , can produce various colors by altering the concentration of the activators. [31][32][33] However, it is hard to achieve efficient multicolor luminescence in a sole material. As a competitive alternative, multimode luminescent materials with down-shifting (DS) and upconversion (UC) luminescence could effectively solve the problems mentioned above.…”