Fluorescent anti-counterfeiting technologies have become indispensable by virtue of their high concealment properties. In this work, the observation of the characteristic emission originated from Eu 2+ and Eu 3+ ions in CaYAl 3 O 7 realizes a dual-mode anti-counterfeiting strategy. The host matrix provides an environment, where blue and red emission could be manipulated with the introduction of Nd 3+ ions for the reduced occupation of Eu 3+ in the sites of Y 3+ ions. Moreover, the photoluminescence spectra of these samples exhibit time and temperature-dependent dynamic changes thanks to the capture and release of carriers in the reconstructed traps induced by Nd 3+ ions. Herein, a multi-stimuli responsive dynamic and static anti-counterfeiting could be achieved in this work.
Traditional functional materials are the mainstream of modern materials science research. Recently, flexible inorganic functional materials have emerged, opening a new area of materials science. Among the multiple flexible inorganic functional materials, flexible inorganic luminescent materials are the most typical ones due to the compatibility between their nanostructure and luminescence, and are the best choice for investigation for new applications in this field. The luminous intensity of flexible inorganic luminescence materials increases with the increase of calcination temperature, but the macroscopic flexibility decreases with the increase of calcination temperature, which leads to the urgent demand of having a flexible inorganic luminescence material with both good macroscopic flexibility and high luminescence. In this paper, the famous inorganic luminous material CaYAl3O7:Eu3+ was successfully prepared by electrospinning into a macroscopically flexible form. The macroscopic flexibility and luminescence of a pure inorganic CaYAl3O7:Eu3+ nanofiber membrane were systematically investigated. After calcining at high temperature, the grain size increases, which is beneficial to luminescence. However, reducing the calcination temperature will further optimize the flexibility of the membrane. At the same calcination temperature, the maximum bending strain of the inorganic CaYAl3O7:Eu3+ nanofiber membrane is about 2.4 times that of the inorganic CaTiO3:Pr3+ nanofiber membrane, and the macroscopic flexibility of the inorganic CaYAl3O7:Eu3+ nanofiber membrane is obviously better than that of the inorganic CaTiO3:Pr3+ nanofiber membrane. This study provides an idea for the preparation of high-temperature macroscopically flexible inorganic functional materials.
Fengjun Chun,Binbin Zhang,Honggang Liu,Wen Deng,Wen Li,Meilin Xie,Chao Luo,Weiqing Yang
A series of Na+ and Pr3+ co-doped orange-emitting CaYAl3O7 (CYAO) phosphors were prepared by a conventional high-temperature solid-state reaction method. The crystalline structure, the luminescence properties and the decay times of the as-prepared samples were systematically investigated by X-ray diffraction (XRD) and steady-state and time-resolved photoluminescence. Under ultraviolet (UV) light and blue light excitation, the CYAO:Pr3+ phosphors exhibited orange photoluminescence emission and show potential for application in warm white LEDs, and the emission spectra of the as-prepared samples in the near-infrared (NIR) region were detected. Furthermore, Na+ ions were designed as charge compensators to maintain the charge balance. The luminescence intensities in the visible and NIR regions can be effectively enhanced by adjusting the doping amounts of Pr3+ ions and Na+ ions. Moreover, the optical spectra of Pr3+ in the CYAO host crystals were calculated by conventional parametric modeling based on the diagonalization of the complete 91 × 91 energy matrix. The calculated optical spectra were in good agreement with the observed ones and the obtained crystal field parameters were also in a reasonable range. This systemic study, and all of the above, will give a deep insight into the luminescence mechanism of the phosphors and then open one way to exploit the new phosphors for white LEDs.
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