A Temporal and Space Anti-counterfeiting Based on the Four-Modal Luminescent Ba₂Zr₂Si₃O₁₂ Phosphors

Abstract

Fluorescent anti-counterfeiting materials have been widely studied due to their high resolution and convenient identification by direct visualization of the color output. To date, the anti-counterfeiting technology of single ultraviolet excitation mode still has security problems because the single mode could be imitated easily. Here, we have successfully developed four modes of anti-counterfeiting from Eu 2+ and Er 3+ co-doped Ba 2 Zr 2 Si 3 O 12 phosphors with photo, long persistent, photo-stimulated, and upconversion luminescence behavior. The as-fabricated phosphors can emit an intense blue-green luminescence originating from the characteristic transition of Eu 2+ ions and exhibit a blue-green long persistent luminescence phenomenon. Moreover, the enhancement of photo-stimulated luminescence that contributed to the effectively increased trap concentration is observed, along with the produced up-conversion phenomenon thanks to the introduction of Er 3+ ions. Notably, the fluorescence rapidly changes from blue-green to stable green luminescence with the delay of excitation time under the excitation of a 980 nm laser diode. Herein, this work realizes the fast down-to up-conversion luminescence output over time, which provides the basis for its possible application in advanced multi-mode anti-counterfeiting.

Recent Progress in Inorganic Afterglow Materials: Mechanisms, Persistent Luminescent Properties, Modulating Methods, and Bioimaging Applications

“…Among rare earth activators, Eu 2+ ion is the most studied one, and it is famous for the green or blue PL in aluminates and silicates, including SrAl 2 O 4 :Eu 2+ , [ 39 ] SrAl 2 O 4 :Eu 2+ ,Dy 3+ , [ 40 ] CaAl 2 O 4 :Eu,Nd, [ 24a,41 ] SrMgSi 2 O 7 :Eu 2+ ,Dy 3+ , [ 42 ] and Ba 2 Zr 2 Si 3 O 12 :Eu 2+ ,Er 3+ . [ 43 ] Actually, Eu 2+ still can emit green, blue, yellow, and red PL depending on different crystal field effects. Normally, the afterglow of Eu 2+ doped samples can last from several minutes to fifty hours.…”

“…Similar rules were also observed in Gd 3 Al 2 Ga 3 O 12 :Ce 3+ ,Cr 3+ and Gd 2 MgTiO 6 :Bi 3+ ,Cr 3+ phosphors, [ 61b,226 ] which shows the special emissions of Ce 3+ (550 nm, green), Cr 3+ (≈720–760 nm, NIR), and Bi 3+ (430 nm, blue), as well as the polychromatic light of them. Yu and co‐workers designed Ba 2 Zr 2 Si 3 O 12 :Eu 2+ ,Er 3+ for blue‐green long PL under 374 nm, [ 43 ] while fast transformation to green up‐conversion luminescence was shown under the 980 nm irradiation.…”

A multicolor‐emitted phosphor for temperature sensing and multimode dynamic anti‐counterfeiting

“…Besides, PSL may be detected under 980 nm NIR laser excitation after UV pre‐stimulation at room temperature. A 980 nm NIR laser is scaled up and irradiated onto the pattern by a concave lens 40 …”

“…A 980 nm NIR laser is scaled up and irradiated onto the pattern by a concave lens. 40 And it emits the same yellow light as PL emission, which is the fourth anti-counterfeiting mode. After scanning the QR code with a mobile phone, the letters "SICCAS" can be displayed (Figure 6C).…”

Multimode-Responsive Luminescence of Er3+ Single-Activated CaF2 Phosphor for Advanced Information Encryption

“…Recently, researchers have been exploring multimode optical anticounterfeiting strategies that combine various luminescent features to enhance security. − One prominent example is the multilevel anticounterfeiting strategy that incorporates multiple luminescent modes, such as up-conversion luminescence (UCL), long persistent luminescence (LPL), photostimulated luminescence (PSL), and thermoluminescence (TL). − This strategy leverages the unique properties of these luminescent modes to create sophisticated anticounterfeiting features. For example, Xia and co-workers have demonstrated a photonic QR code by synergistically integrating three different light-emitting modes (PL, LPL, and UCL) in a single NaGdTi 2 O 6 :Pr 3+ ,Er 3+ material, and a very high information capacity is obtained through consolidating the QR code and the corresponding color information .…”