Here, we have developed a novel ultra long ultraviolet-A afterglow material CaMgGeO 4 : Bi 3+ , which shows more than 24 h UVA afterglow emission peaked at 346 nm. The crystal structure shows that the prepared sample is a pure phase with an orthogonal system of Pmnb space group. The composition of valence band and conduction band was analyzed by the density of states , which reveals that the bandgap of the CaMgGeO 4 matrix is 3.69 eV. The photoluminescence spectrum of the sample consists of a broadband in the 320–400 nm UVA region, which belongs to the 3 P 1 → 1 S 0 electron transition of Bi 3+ . More importantly, under the excitation of ultraviolet lamp for 3 min, CaMgGeO 4 : Bi 3+ exhibited an UVA ultra long persistent luminescence (LPL) with a duration of more than 24 h, which afterglow emission intensity still reaches 1500 cps and is about 6 times of the background intensity. In addition, the UVA emission of CaMgGeO 4 : Bi 3+ after 13 h day can be repeatedly by short periods of low-energy light sources stimulation. The thermoluminescence analysis indicates that the presence of shallow and deep traps is responsible for excellent UVA-LPL and photo-stimulate luminescence (PSL). The excellent LPL and PSL properties can prompt CaMgGeO4: Bi 3+ phosphor to be widely used in the field of photodynamic therapy.
Hanyu Hu,Zeyu Lyu,Dashuai Sun,Shuai Wei,Jia Liu,Xin Wang,Luhui Zhou,Hongpeng You
Although there have been numerous reports on broadband near-infrared (NIR) emitting phosphors, their emissions are mainly concentrated in the range of 700–1000 nm (NIR-I). Herein, we successfully synthesized a broadband near-infrared phosphor CaMgGeO4:Cr4+(CMG:Cr4+) with an emission in the range of 1000–1600 nm (NIR-II). The introduction of Er3+ ions into CMG:Cr4+ resulted in a wider near-infrared emission phosphor CaMgGeO4:Cr4+,Er3+ (fwhm = 361 nm), compensating for the luminescence of 1500–1600 nm. More importantly, an energy transfer from Cr4+ to Er3+ ions has been discovered. Furthermore, a NIR pc-LED was fabricated by combining the CMG:Cr4+,Er3+ phosphor with a 590 nm chip. The changes in intensity and profile of the transmission spectra of light passing through different liquids reveal its potential application in organic compound recognition. This work opens a direction for the development of NIR-II phosphors.
Here, we successfully synthesized the fast-X-ray-charged UV-visible mechanoluminescence (ML) phosphor CaMgGeO4:Tb3+. Fast X-ray charging (only 10 s of irradiation) can induce strong ML from CaMgGeO4:Tb3+, and the ML intensity reaches saturation after only 3 min of X-ray charging. The strong ultraviolet-blue ML emission (380 and 416 nm) of CaMgGeO4:Tb3+ can be used as an excitation source to effectively stimulate LED phosphors to produce ML emission of various colors. At the same time, there is a certain linear relationship between the ML intensity of the sample and the compressive load, indicating that the applied force can be accurately detected. According to the thermoluminescence results, the long-term and stable ML emission of CMG:Tb3+ is due to the continuous distribution of deep traps. The large number of deeply trapped electrons allows the long-term detection of stress bursts. After one-time X-ray charging for 3 min, even after a delay of 84 h, the signal-to-noise ratio can still reach 1.3 (2500 N) and 1.7 (3000 N) in multiple cycles of stress burst detection. The results have shown that CaMgGeO4:Tb3+ can not only be regarded as an efficient excitation source to realize various colors of ML emission, but it can also serve as a sensor to monitor potential force bursts over extended periods, which would expand the application of ML sensors.
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