掺铥硫氧化钇的特殊余辉性质

迄今为止,稀土长余辉磷光体已见文献或专利公开报道的激活离子主要有适于紫外光激发的三价铈离子(Ce³⁺)和三价镨离子(Pr³⁺)、适于可见光激发的铕离子(Eu³⁺和Eu²⁺)及钐离子(Sm³⁺,Sm²⁺),尚未涉及到铥离子Tm³⁺或Tm²⁺.我们在Tm³⁺离子激活的硫氧化钇体系Y₂O₂S:Tm³⁺中发现了长余辉荧光特性.特别是在该磷光体中还发现了一种非常特殊的余辉现象.     

UV Induced Afterglow in Europium-Doped Alkali Bromides at Low Temperature

This work presents a study of the afterglow (AG) luminescence induced by UV radiation at 20 K in Eu doped KBr. The analysis of the AG data reveals at least two components: one of them decays quickly during the first seconds after irradiation and the other one extends over several minutes. The excitation-emission spectra of the AG and the thermoluminescence (TL) for a KBr:Eu sample are compared with those measured under identical conditions for a pure KBr. We conclude that the origin of the fast-AG is mainly intrinsic and the slow-AG is dominated by the Eu impurity luminescence. We confirm that the excitation-emission bands of the slow-AG also appear in the TL suggesting a close relation between the slow-AG and the TL. Additionally we found another TL band in the pure crystal that could not be related to the AG.     

Development and fundamental investigation of Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS)

Glow Discharge (GD) spectroscopy is a well known and accepted technique for the bulk and surface composition analysis, while laser ablation (LA) provides analysis with high spatial-resolution analysis in LIBS (laser-induced breakdown spectroscopy) or when coupled to inductively coupled plasma spectrometry (ICP-OES or ICP-MS). This work concerns the construction of a Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS) instrument to study the analytical capabilities resulting from the interaction of a laser-generated sample plume with a pulsed glow discharge. Two ablation configurations were studied in detail. In a first approach, the laser-generated plume was introduced directly into the GD, while the second approach generated the plume inside the GD. The ablated material was introduced at different times with respect to the discharge pulse in order to exploit the efficient ionization in the GD plasma. For both LA-GD configurations, direct ablation into the afterglow of the pulsed glow discharge leads to an ion signal enhancement of up to a factor of 7, as compared to the ablation process alone under the same experimental conditions. The LA-GD enhancement was found to occur exclusively in the GD afterglow, with a maximum ablation S/N occurring in a few hundred microseconds after the termination of the glow discharge. The duration of the enhanced signal is about two milliseconds. Both the laser pulse energy and the position of the ablation plume (with respect to the sampling orifice) were found to affect the amount of mass entering the afterglow region and consequently, the enhancement factor of ionization.     

Trapping mechanism in the afterglow process of the rare-earth activated Y2O2S phosphors

Phosphorescence properties are investigated in Y₂O₂S phosphors doped with rare-earth (lanthanoid, Ln) ions. Luminescence afterglow with a decay time of several ten milliseconds is observed at room temperature in the phosphors activated by Nd, Sm, Eu, Dy, Ho, Tm, Er, and Yb. The depths (thermal activation energies) of the traps causing the afterglow are measured with the transient luminescence method.It is concluded that the excited electron and the hole in the conduction and valence bands are trapped separately in the states (impurity levels) located in the vicinity of the Ln³⁺ ion. The trapping depths of the level range from 0.3 to 1.1 eV and are dependent on the electron affinity of the Ln³⁺ ion estimated from the energy difference between the 4fⁿ⁺¹ and the 4fⁿ configurations in the 4f shell of the ion.     

Ultra-long Near-infrared Repeatable Photochemical Afterglow Mediated by Reversible Storage of Singlet Oxygen for Information Encryption

Photochemical afterglow systems have drawn considerable attention in recent years due to their regulable photophysical properties and charming application potential. However, conventional photochemical afterglow suffered from its unrepeatability due to the consumption of energy cache units as afterglow photons are emitted. Here we report a novel strategy to realize repeatable photochemical afterglow (RPA) through the reversible storage of ¹O₂ by 2-pyridones. Near-infrared afterglow with a lifetime over 10 s is achieved, and its initial intensity shows no significant reduction over 50 excitation cycles. A detailed mechanism study was conducted and confirmed the RPA is realized through the singlet oxygen-sensitized fluorescence emission. Furthermore, the generality of this strategy is demonstrated and tunable afterglow lifetimes and colors are achieved by rational design. The developed RPA is further applied for attacker-misleading information encryption, presenting a repeatable-readout.     

A Heavy-atom-free Molecular Motif Based on Symmetric Bird-like Structured Tetraphenylenes with Room-Temperature Phosphorescence (RTP) Afterglow over 8 s

In recent years, pure organic room-temperature phosphorescence (RTP) with highly efficient and long-persistent afterglow has drawn substantial awareness. Commonly, spin-orbit coupling can be improved by introducing heavy atoms into pure-organic molecules. However, this strategy will simultaneously increase the radiative and non-radiative transition rate, further resulting in dramatic decreases in the excited state lifetime and afterglow duration. Here in this work, a highly symmetric bird-like structure tetraphenylene (TeP), and its three symmetrical halogenated derivatives (TeP−F, TeP−Cl and TeP−Br) are synthesized, while their RTP properties and mechanisms are systematically investigated by both theoretical and experimental approaches. As the results, the rigid, highly twisted conformation of TeP restricts the non-radiative processes of RTP and gives rise to the enhancement of electron-exchange, which can contribute to the RTP radiation process. Despite the faint RTP of the bromine and chlorine-substituted ones (TeP−Br, TeP−Cl), the fluoro-substituted TeP−F exhibited a long phosphorescent lifetime up to 890 ms, corresponding to an extremely long RTP afterglow over 8 s, which could be incorporated into the best series of non-heavy-atom RTP materials reported in previous literature.     

Room-Temperature Multiple Phosphorescence from Functionalized Corannulenes: Temperature Sensing and Afterglow Organic Light-Emitting Diode**

Corannulene-derived materials have been extensively explored in energy storage and solar cells, however, are rarely documented as emitters in light-emitting sensors and organic light-emitting diodes (OLEDs), due to low exciton utilization. Here, we report a family of multi-donor and acceptor (multi-D-A) motifs, TCzPhCor, TDMACPhCor, and TPXZPhCor, using corannulene as the acceptor and carbazole (Cz), 9,10-dihydro-9,10-dimethylacridine (DMAC), and phenoxazine (PXZ) as the donor, respectively. By decorating corannulene with different donors, multiple phosphorescence is realized. Theoretical and photophysical investigations reveal that TCzPhCor shows room-temperature phosphorescence (RTP) from the lowest-lying T₁; however, for TDMACPhCor, dual RTP originating from a higher-lying T₁ (T₁^H) and a lower-lying T₁ (T₁^L) can be observed, while for TPXZPhCor, T₁^H-dominated RTP occurs resulting from a stabilized high-energy T₁ geometry. Benefiting from the high-temperature sensitivity of TPXZPhCor, high color-resolution temperature sensing is achieved. Besides, due to degenerate S₁ and T₁^H states of TPXZPhCor, the first corannulene-based solution-processed afterglow OLEDs is investigated. The afterglow OLED with TPXZPhCor shows a maximum external quantum efficiency (EQE_max) and a luminance (L_max) of 3.3 % and 5167 cd m⁻², respectively, which is one of the most efficient afterglow RTP OLEDs reported to date.     

快速溶胶-凝胶法制备SrAl2O4：Eu^2＋,Dy^3＋绿色长余辉荧光粉及表征

建立一种快速溶胶-凝胶法制备长余辉材料的方法。以柠檬酸,硝酸锶,硝酸铝及硝酸铕等为原料,实现了该法的快速制备过程。研究结果表明,通过改进可使该法制备铝酸锶长余辉材料的时间缩短至12h以内,X射线粉末衍射,扫描电镜,光谱分析等表明,使用该方法与传统溶胶-凝胶法制备的样品其性能基本一致。     

The structure and luminescence properties of long afterglow phosphor Y3−xMnxAl5−xSixO12

A series of phosphors with the composition Y_3−xMn_xAl_5−xSi_xO₁₂ (x=0, 0.025, 0.050, 0.075, 0.150, 0.225, 0.300) were prepared with solid state reactions. The X-ray powder diffraction analysis of samples shows that the substitution of Mn²⁺ and Si⁴⁺ does not change the garnet structure of phosphors, but makes the interplanar distance decrease to a certain extent. The emission spectra show that Mn²⁺ in Y₃Al₅O₁₂ emits yellow-orange light in a broad band. With the increment of substitution content, the emission intensity of the phosphors increases firstly then decreases subsequently, and the emission peak moves to longer wavelength. Afterglow spectra and decay curves show that all the Mn²⁺ and Si⁴⁺ co-doped samples emit yellow-orange light with long afterglow after the irradiation of ultraviolet light. The longest afterglow time is 18 min. Thermoluminescence measurement shows that there exist two kinds of traps with different depth of energy level and their depth decreases with the increment of substitution content.     

Color-Tunable Dual-Mode Organic Afterglow from Classical Aggregation-Caused Quenching Compounds for White-Light-Manipulated Anti-Counterfeiting

Color-tunable dual-mode organic afterglow excited by ultraviolet (UV) and white light was achieved from classical aggregation-caused quenching compounds for the first time. Specifically, two luminescent systems, which could produce significant organic afterglow composed of persistent thermally activated delayed fluorescence and ultralong organic phosphorescence under ambient conditions, were constructed by doping fluorescein sodium and calcein sodium into aluminum sulfate. Their lifetimes surpassed 600 ms, and the dopant concentrations were as low as 5×10⁻⁶ wt %. Moreover, the persistent luminescence colors of the materials could be tuned from blue to green and then to yellow by simply varying the concentrations of guest compounds or the temperature in the range of 260–340 K. Inspired by these exciting results, the afterglow materials were used for UV- and white-light-manipulated anti-counterfeiting and preparation of elastomers with different colors of persistent luminescence.