Physics

Multicolor sustained luminescent material for dynamic optical anti-counterfeiting

Written by Light Publishing Center, Changchun Optical Research Institute, Precision Mechanical Physics, CAS

(a) Normalized excitation wavelength-dependent PersL spectrum of CaGa1.97O4:0.5%Bi (irradiation time 5 min, interval 1 min). (b) Sustained decay monitored at the corresponding wavelength after 5 min of xenon lamp excitation from 240 to 440 nm. (c) Tunable PersL color trajectory recorded when changing the excitation wavelength from 240 to 440 nm. (d) Ultraviolet color chart showing the ability to visually detect specific wavelengths in the ultraviolet region using CaGa1.97O4:0.5%Bi. Credit: Bo-Mei Liu, Yue Lin, Yingchun Liu, Bibo Lou, Chong-Geng Ma, Hui Zhang, Jing Wang

Optical anti-counterfeiting technology has deeply penetrated into our daily life as a preventive measure. Visually readable codes designed based on optical materials are widely used because they are easy to verify, affordable, and difficult to replicate. With the rapid development of modern technology and the prevalence of counterfeiting, optical anti-counterfeiting technology faces great challenges. As a result, optical anti-counterfeit material systems based on multimodal integrated applications have attracted wide attention.

In a new paper published in Light: Science & Applications, a team of scientists led by Professor Jing Wang from the Key Laboratory of Bioinorganic and Synthetic Chemistry, the National Key Laboratory of Optoelectronic Materials and Technology, and the Sun College of Cultural Studies, Ministry of Education. , Sen University, China, and their collaborators have developed a non-stoichiometric sustained luminescence (PersL) inorganic material, CaGaxO4:Bi (x < 2), that can respond to various UV stimuli.

This material exhibits a color change of PersL depending on the excitation wavelength, thereby exhibiting excitation wavelength-dependent emission properties. Under the stimulation of different UV wavelengths, steady and sustained luminescence of three different colors, green, yellow, and orange, can be achieved.

When the excitation wavelength is changed continuously from approximately 240 nm to 400 nm, the corresponding emission wavelength changes from 605 nm to 540 nm, indicating the ability of the material to visualize in response to specific UV wavelengths.

Multicolor sustained luminescent material for dynamic optical anti-counterfeiting

(a) Schematic diagram of the experimental setup for varying the excitation wavelength from 240 to 440 nm to achieve a multicolor display. (b) Schematic diagram and optical image of the prepared composite film. (c) PersL photo of colorful fish and cat patterns recorded on composite film. Note that the green and yellow parts were recorded after switching off the handheld lighter at 365 nm and 254 nm, respectively. (d) Poker pattern of hearts, clubs, and diamonds obtained simultaneously by randomly placing 254/340/365 nm light from a xenon lamp through a mask. (e), (f) Images are hand-held color and time-dependent PersL images of figure “8” pre-illuminated at 254 nm (yellow area, 10 s) and 365 nm (green area, 3 min) is. writer. Note that the top image inside the open circle is a simulation pattern based on the PersL image. The pattern on the right is the saved information. Scale bar: 1 cm. Credit: Bo-Mei Liu, Yue Lin, Yingchun Liu, Bibo Lou, Chong-Geng Ma, Hui Zhang, Jing Wang

In contrast to conventional inorganic PersL materials that can display only monochromatic afterglow images, in this study we present a composite film of polydimethylsiloxane (PDMS) prepared from a single component material system that can display multicolor afterglow patterns. Introducing. The response of a material to afterglow at a particular excitation wavelength is exploited by using different optical masks to display different colors and patterns at different UV excitations.

Furthermore, by controlling the excitation wavelength and irradiation time, we realize a new information storage mode that encodes the afterglow color and duration. By setting the irradiation time and pattern of the 254nm and 365nm light sources, you can control the display time of the yellow and green digital persistence patterns on the composite film. Afterglow digital patterns of different colors have observation windows, leading to the development of new information reading/writing modes.

The researchers briefly outlined the design principles and expected application scenarios. “We propose applying color and time-resolved PersL properties to writing, reading, and displaying information.

“Main advances include: Polychromatic PersL materials with excitation wavelength-dependent properties have been prepared by non-stoichiometric design. Experimental and theoretical studies reveal the basis of the unique luminescent effect. The unique multicolor PersL properties can be exploited for UV detection, anti-counterfeiting, information storage and Applications of this material in cryptography are being considered. ”

Further information: Bo-Mei Liu et al. Excitation wavelength-dependent sustained emission from single-component non-stoichiometric CaGaxO4:Bi for dynamic anti-counterfeiting, Light: Science & Applications (2024). DOI: 10.1038/s41377-024-01635-7

Provided by: Light Publishing Center, Changchun Institute of Optics, Fine Mechanics and Physics, CAS

Citation: Multicolor Persistent Luminescent Materials for Dynamic Optical Anti-Counterfeiting (October 15, 2024), https://phys.org/news/2024-10-multicolor-persistent-luminescent on October 15, 2024 Retrieved from -materials-dynamic.html

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