Abstract
A significant impediment to the deployment of anti-counterfeiting technologies is the reliance on specialized hardware. Here, anti-counterfeiting labels are developed that are both excited and detected using a smartphone. The persistent luminescence pattern and color changes on the timescale of hundreds of milliseconds to seconds. The labels can be authenticated by comparing still images from the red and green channels of video acquired at known times after flashlight excitation against expected reference patterns. The labels are based on a green-emitting SrAl2O4: Eu2+,Dy3+ (SAED), and red-emitting CaS:Eu2+ phosphors whose lifetimes are varied: (i) for SAED from 0.5 to 11.7 s by annealing the commercial material in air; and (ii) CaS:Eu2+ from 0.1 to 0.6 s by varying the dopant concentration. Examples of anti-counterfeiting labels exhibiting changing emission patterns and colors on a seven-segment display, barcode, and emoji are demonstrated. These results demonstrate that phosphors with visible absorption and tunable persistent luminescence lifetimes on the order of hundreds of milliseconds to seconds are attractive for anti-counterfeiting applications as they allow authentication to be performed using only a smartphone. Further development should allow richer color shifts and enhancement of security by embedding further covert anti-counterfeiting features.
Highlights
A significant impediment to the deployment of anti-counterfeiting technologies is the reliance on specialized hardware
For the red-emitting phosphor, the initial emission at time zero is uniformly bright, but the subsequent frames demonstrate the varied persistent lifetimes that decrease with the increase in E u2+ doping
It is clear from the frames that to 2 s, whereas tthheeCCaa00.9.98959SS::EEuu2020+.0+.01051eexxhhiibbiittss aa longer red persistent luminescence decay that is observable up very short persistent luminescence decay observable up to only
Summary
A significant impediment to the deployment of anti-counterfeiting technologies is the reliance on specialized hardware. 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 Scientific Reports | (2022) 12:2100 |
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