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1. Gd ³⁺ -activated narrowband ultraviolet-B persistent luminescence through persistent energy transfer

   https://doi.org/10.1039/D1DT00120E  

   Wang, Xianli ; Chen, Yafei ; Kner, Peter A. ; Pan, Zhengwei ( March 2021 , Dalton Transactions)

   This work reports the realization of Gd 3+ persistent luminescence in the narrowband ultraviolet-B (NB-UVB; 310–313 nm) through persistent energy transfer from a sensitizer of Pr 3+ , Pb 2+ or Bi 3+ . We propose a general design concept to develop Gd 3+ -activated NB-UVB persistent phosphors from Pr 3+ -, Pb 2+ - or Bi 3+ -activated ultraviolet-C (200–280 nm) or ultraviolet-B (280–315 nm) persistent phosphors, leading to the discovery of ten Gd 3+ NB-UVB persistent phosphors such as Sr 3 Gd 2 Si 6 O 18 :Pr 3+ , Sr 3 Gd 2 Si 6 O 18 :Pb 2+ and Y 2 GdAl 2 Ga 3 O 12 :Bi 3+ as well as five ultraviolet-B persistent phosphors such as Y 3 Al 2 Ga 3 O 12 :Pr 3+ , Sr 3 Y 2 Si 6 O 18 :Pb 2+ and Y 3 Al 2 Ga 3 O 12 :Bi 3+ . The persistent energy transfer from the sensitizers to Gd 3+ is very efficient and the Gd 3+ NB-UVB afterglow can last for more than 10 hours. This study expands the persistent luminescence research to the NB-UVB as well as the broader ultraviolet-B spectral regions. Themore »NB-UVB persistent phosphors may act as self-sustained glowing NB-UVB radiation sources for dermatological therapy.« less
2. A new up-conversion charging concept for effectively charging persistent phosphors using low-energy visible-light laser diodes

   https://doi.org/10.1039/C8TC02419G  

   Chen, Yafei ; Liu, Feng ; Liang, Yanjie ; Wang, Xianli ; Bi, Jianqiang ; Wang, Xiao-jun ; Pan, Zhengwei ( January 2018 , Journal of Materials Chemistry C)

   It is general knowledge in persistent luminescence that high-energy illumination, mostly ultraviolet light, is usually necessary in order to effectively charge persistent phosphors. However, the need for high-energy ultraviolet light excitation compromises some applications. In his pioneering work on ruby (Al 2 O 3 :Cr 3+ ) laser materials in 1960, Theodore Maiman observed an excited-state absorption phenomenon under the excitation of a high-intensity green-light flash tube. Inspired by Maiman's observation, here we propose a new two-photon up-conversion charging (UCC) concept to effectively charge Cr 3+ -activated near-infrared persistent phosphors using low-energy, high-intensity visible-light laser diodes. As an example, we demonstrate that a low-energy 635 nm laser diode can produce persistent luminescence in the LiGa 5 O 8 :Cr 3+ persistent phosphor at the same magnitude as that produced by high-energy 335 nm ultraviolet light from a xenon arc lamp. Moreover, the UCC appears to be a common phenomenon in persistent phosphors containing other UCC-enabling activators such as rare-earth Pr 3+ ions and transition metal Mn 2+ ions. The UCC technique offers a new way to study persistent luminescence and utilize persistent phosphors; for instance, in bioimaging it makes effective in vivo charging persistent optical probes using tissue-friendly visible lightmore »possible.« less
3. Near-infrared photoluminescence of Portland cement

   https://doi.org/10.1038/s41598-022-05113-1  

   Meng, Wei ; Bachilo, Sergei M. ; Parol, Jafarali ; Nagarajaiah, Satish ; Weisman, R. Bruce ( January 2022 , Scientific Reports)

   Portland cement emits bright near-infrared photoluminescence that can be excited by light wavelengths ranging from at least 500–1000 nm. The emission has a peak wavelength near 1140 nm and a width of approximately 30 nm. Its source is suggested to be small particles of silicon associated with calcium silicate phases. The luminescence peak wavelength appears independent of the cement hydration state, aggregates, and mechanical strain but increases weakly with increasing temperature. It varies slightly with the type of cement, suggesting a new non-contact method for identifying cement formulations. After a thin opaque coating is applied to a cement or concrete surface, subsequent formation of microcracks exposes the substrate’s near-infrared emission, revealing the fracture locations, pattern, and progression. This damage would escape detection in normal imaging inspections. Near-infrared luminescence imaging may therefore provide a new tool for non-destructive testing of cement-based structures.
4. Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation

   https://doi.org/10.5194/bg-16-561-2019  

   Tong, Shanying ; Hutchins, David A. ; Gao, Kunshan ( January 2019 , Biogeosciences)

   Abstract. Marine phytoplankton such as bloom-forming, calcite-producingcoccolithophores, are naturally exposed to solar ultraviolet radiation (UVR,280–400nm) in the ocean's upper mixed layers. Nevertheless, the effects ofincreasing carbon dioxide (CO₂)-induced ocean acidification and warming have rarelybeen investigated in the presence of UVR. We examined calcification andphotosynthetic carbon fixation performance in the most cosmopolitancoccolithophorid, Emiliania huxleyi, grown under high(1000µatm, HC; pH_T: 7.70) and low (400µatm,LC; pH_T: 8.02) CO₂ levels, at 15^∘C,20^∘C and 24^∘C with or without UVR. The HCtreatment did not affect photosynthetic carbon fixation at 15^∘C,but significantly enhanced it with increasing temperature. Exposure to UVRinhibited photosynthesis, with higher inhibition by UVA (320–395nm) thanUVB (295–320nm), except in the HC and 24^∘C-grown cells, in whichUVB caused more inhibition than UVA. A reduced thickness of the coccolith layerin the HC-grown cells appeared to be responsible for the UV-inducedinhibition, and an increased repair rate of UVA-derived damage in theHC–high-temperature grown cells could be responsible for lowered UVA-induced inhibition.While calcification was reduced with elevated CO₂ concentration,exposure to UVB or UVA affected the process differentially, with the formerinhibiting it and the latter enhancing it. UVA-induced stimulationmore »of calcification washigher in the HC-grown cells at 15 and 20^∘C, whereas at24^∘C observed enhancement was not significant. The calcificationto photosynthesis ratio (Cal∕Pho ratio) was lower in the HC treatment,and increasing temperature also lowered the value. However, at 20 and24^∘C, exposure to UVR significantly increased the Cal∕Phoratio, especially in HC-grown cells, by up to 100%. This implies thatUVR can counteract the negative effects of the “greenhouse” treatment onthe Cal∕Pho ratio; hence, UVR may be a key stressor when considering theimpacts of future greenhouse conditions on E. huxleyi.

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5. The emergence of diffused gamma-ray burst afterglows from the discs of active galactic nuclei

   https://doi.org/10.1093/mnras/stac1968  

   Wang, Yi-Han ; Lazzati, Davide ; Perna, Rosalba ( July 2022 , Monthly Notices of the Royal Astronomical Society)

   The discs of active galactic nuclei (AGNs) have emerged as rich environments for the production and capture of stars and the compact objects that they leave behind. These stars produce long gamma-ray bursts (GRBs) at their deaths, while frequent interactions among compact objects form binary neutron stars and neutron star–black hole binaries, leading to short GRBs upon their merger. Predicting the properties of these transients as they emerge from the dense environments of AGN discs is key to their proper identification and to better constrain the star and compact object population in AGN discs. Some of these transients would appear unusual because they take place in much higher densities than the interstellar medium. Others, which are the subject of this paper, would additionally be modified by radiation diffusion, since they are generated within optically thick regions of the accretion discs. Here, we compute the GRB afterglow light curves for diffused GRB sources for a representative variety of central black hole masses and disc locations. We find that the radiation from radio to ultraviolet and soft X-rays can be strongly suppressed by synchrotron self-absorption in the dense medium of the AGN disc. In addition, photon diffusion can significantly delay themore »emergence of the emission peak, turning a beamed, fast transient into a slow, isotropic, and dimmer one. These would appear as broad-band correlated AGN variability with a dominance at the higher frequencies. Their properties can constrain both the stellar populations within AGN discs and the disc structure.

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