Persistent luminescence (PersL) has drawn intense attention because of its widely practical applications. Dynamic color-tunable PersL is desired and fascinating for advanced anti-counterfeiting, information storage, etc. However, it is difficult to obtain and rarely reported. Herein, a simple and effective method by using coordination polymers (CPs) as precursors is designed for color-tunable zinc-cadmium silicate composites PersL phosphors. Compared with pure Zn 2 SiO 4 (ZSO) and CdSiO 3 (CSO), the composites (ZSO/CSO) exhibit significantly improved brightness and dynamic tunable color. With time evolution, the color varied from white to yellow to orange and finally even to red. Notably, the duration time of 1.0 % Dy 3+ doped ZSO/CSO is prolonged to 19000 s (>5 h) at the threshold value (0.32 mcd/m 2 ) after 254 nm irradiation, showing a more than 100-fold enhancement compared with CSO. In attempt to achieve a better understanding of the enhanced mechanisms, the formation energy of Dy 3+ and O-vacancy are accurately derived from first-principles calculations. Combined with thermoluminescence (TL) measurement, the PersL mechanism is proposed. Finally, the application of ZSO/CSO:1.0 % Dy 3+ in displaying and anti-counterfeiting was explored. This work not only provides a new way to the design of PersL phosphors through composite compounds, but also promotes the development of PersL phosphors in practical applications.
Panqin Wang,Jiaren Du,Tengyue Wang,Shaoxing Lyu,Rik Van Deun,Dirk Poelman,Hengwei Lin
Despite the substantial progress made, the responsiveness of thermo-responsive materials upon various thermal fields is still restricted to monochromatic visualization with single-wavelength light emission. This stems from a poor understanding of the photophysical processes within the materials and the unvarying optical performance of luminescent centers’ response to various ambient temperatures. Conventional techniques to assess the inhomogeneities of thermal fields can be time-consuming, require specialized equipment and suffer from inaccuracy due to the inevitable interference from background signals, especially at high temperature. To this end, we overcome these limitations for the first time, to flexibly visualize temperature inhomogeneities by developing a thermochromic smart material, SrGa12−xAlxO19:Dy3+. Two distinct modes of thermochromic properties (steady-state temperature-dependent luminescence and thermally stimulated luminescence) are investigated. It is revealed that the abundant colors (from yellow, green to red) and amazing color-changing features are due to the superior optical integration of the host (SrGa12−xAlxO19) and dopant (Dy3+) emissions under specific thermal stimulations. We suggest that this thermo-responsive smart material can be used to realize highly efficient and simple visualization of invisible thermal distribution in industry and beyond.
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