Anticounterfeiting Labels with Smartphone‐Readable Dynamic Luminescent Patterns Based on Tailored Persistent Lifetimes in Gd₂O₂S:Eu³⁺/Ti⁴⁺

Abstract

Dynamic luminescent labels, in which a luminescent image changes with time after ultraviolet excitation is turned off, are attractive for anticounterfeiting. A sequence of Gd2O2S:Eu3+/Ti4+ phosphors is presented in which the Ti4+ doping concentration allows the persistent emission lifetime to be varied from 1.17 ± 0.02 to 5.95 ± 0.07 s. While this persistent lifetime is tuned, the photoluminescence quantum yield remains over 46% ± 3%. A broad charge‐transfer band allows these phosphors to be excited with inexpensive and relatively safe 375 nm light‐emitting diodes. By developing patterns with phosphors that have differing persistent lifetimes, dynamic changes in the luminescent image after the excitation source is removed can be observed. For patterns made from phosphor materials that have big differences in persistent lifetimes, these dynamic changes are observable by the eye. By contrast, the dynamic changes in patterns made by phosphors with comparable persistent lifetimes (0.20 s delayed lifetime difference) are difficult to observe by the naked eye but can be easily determined by analysis of a 30‐frames‐per‐second video taken with a smartphone. Thus, these bright phosphors with tunable persistent lifetime allow both overt (observable by eye) and covert (requiring smartphone video analysis) dynamic anticounterfeiting labels to be created.

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

“…Secondly, there should be sufficient emission from the excited anti-counterfeiting material that can be detected with the smartphone camera in a darkened environment. Thirdly, to achieve a dynamic shift in the emission pattern of the anti-counterfeiting labels should contain phosphors with varied persistent lifetimes as already demonstrated in the authors’ previous work 26 . Finally, to achieve a shift in color in the dynamic pattern, a blend of two or more phosphors with different emission spectra is required.…”

“…demonstrated the use of ultra-long lifetimes (up to 350 ms) using carbon dots in zeolite matrices with a photoluminescence quantum yield (PLQY) of up to 52% allowing post UV excitation observation with the naked eye 18 . The authors’ previous work advanced on this approach by developing smartphone-camera-readable dynamic anti-counterfeiting labels based on Gd 2 O 2 S: Eu 3+ /Ti 4+ phosphor 26 . Dynamic patterns were realized via the Ti 4+ co-doping that allowed the persistent lifetime to be tuned from 1.2 to 5.6 s 26 .…”

“…The authors’ previous work advanced on this approach by developing smartphone-camera-readable dynamic anti-counterfeiting labels based on Gd 2 O 2 S: Eu 3+ /Ti 4+ phosphor 26 . Dynamic patterns were realized via the Ti 4+ co-doping that allowed the persistent lifetime to be tuned from 1.2 to 5.6 s 26 . However, for these labels, a UV light source was required for exciting the labels before video-recording the emission for subsequent PL-lifetime analysis.…”

Sustainable Smart Tags with Two‐Step Verification for Anticounterfeiting Triggered by the Photothermal Response of Upconverting Nanoparticles

“…[ 16–20 ] Since UCNPs present singular spectroscopic features such as sharp emission bands, long excited‐state lifetimes, and photostable response, [ 21 ] it is possible to envisage smart tags based on QR codes containing UCNPs that present a unique luminescent response provided by NIR excitation sources. [ 22–27 ] Although several luminescent materials display light‐emitting properties under ultraviolet (UV) excitation, [ 15,28,29 ] the use of smart tags containing UCNPs provide a step further in anticounterfeiting applications because NIR excitation is more difficult to replicate. Furthermore, NIR irradiation does not give rise to downshifting light emission from conventional luminescent materials, avoiding interference from background luminescence during the readout of the QR code.…”

Hybrid Inorganic–Organic Luminescent Supraparticle Taggants with Switchable Dual‐Level ID

“…[ 2–6 ] Additionally, developments in the digitalization of manufacturing could be fostered by the realization of the Internet of Things, thanks to programmable ID taggants. [ 7–9 ] Moreover, ID taggants could contribute to the establishment of transparent global trading networks and prevent product counterfeiting, thereby improving quality assurance. [ 10–13 ]…”