Reviewed by Lexie CornerOct 16 2024
Researchers from Sun Yat-sen University have created a non-stoichiometric persistent luminescence (PersL) inorganic material, CaGaxO4:Bi (x < 2), that can react to a variety of UV light stimuli. The study was published in the journal Light: Science & Application.
(a) Normalized excitation-wavelength-dependent PersL spectra of CaGa1.97O4:0.5%Bi (irradiation time, 5 min; interval, 1 min). (b) Persistent decay monitored at the corresponding wavelength after 5 min of xenon lamp excitation from 240 to 440 nm. (c) The trajectory of tunable PersL colors 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 range using CaGa1.97O4:0.5 %Bi. Image Credit: Bo-Mei Liu, Yue Lin, Yingchun Liu, Bibo Lou, Chong-Geng Ma, Hui Zhang, and Jing Wang
Optical anti-counterfeiting technology has become a common preventative measure in daily life. Visually readable codes based on optical materials are often used because they are difficult to replicate, cost-effective, and easy to verify.
The rapid advancement of modern technology and the increasing prevalence of counterfeiting have posed new challenges for optical anti-counterfeiting technology. As a result, optical anti-counterfeiting materials that rely on multimodal integrated applications have garnered significant attention.
The material created by Sun Yat-sen researchers exhibits excitation-wavelength-dependent emission, where its PersL changes color based on the excitation wavelength. It can produce stable luminescence in green, yellow, and orange when stimulated by different ultraviolet wavelengths.
The material's response to specific ultraviolet wavelengths is demonstrated by the emission wavelength shifting from 605 nm to 540 nm as the excitation wavelength changes from around 240 nm to 400 nm.
This study introduces a composite film of polydimethylsiloxane (PDMS) made from a single-component material system that can display multicolor afterglow patterns. Unlike traditional inorganic PersL materials that only show single-color afterglow images, this material allows for multicolor afterglow patterns.
Using different optical masks, distinct colors and patterns can be displayed under varying UV excitations. A new information storage mode has also been developed, in which the afterglow color and duration can be controlled by adjusting the excitation wavelength and irradiation time.
Additionally, the display duration of yellow and green afterglow patterns in the composite film can be regulated by adjusting the irradiation time and patterns of 254 nm and 365 nm light sources. This introduces a novel information read-write mode, enabling the observation of distinct colored afterglow patterns.
The researchers added, “We propose the application of color- and time-resolved PersL properties for information writing, reading, and display. The main breakthroughs are as follows: (1) A multicolor PersL material with excitation-wavelength-dependent properties was prepared by a non-stoichiometric design; (2) Experimental and theoretical studies have substantiated the mechanism underlying the distinct luminescence effect and demonstrated the feasibility of the defect engineering strategy in fabricating materials with PersL; and (3) Taking advantage of the distinct multicolor PersL properties, the applications of this material in UV detection, anti-counterfeiting, and information storage and encryption have been explored.”
Journal Reference:
Liu, B.-M., et al. (2024) Excitation-wavelength-dependent persistent luminescence from single-component nonstoichiometric CaGaxO4:Bi for dynamic anti-counterfeiting. Light Science & Applications. doi.org/10.1038/s41377-024-01635-7.