Highly two-photon and X-ray excited long-persistent luminescence in a crystalline host-guest aggregate

As a unique type of supramolecular self-assemblies,crystalline host-guest aggregates have attracted extensive interests in multiple application fields.Herein,a crystalline host-guest aggregate LIFM-HG1 was obtained with curcubit[8]uril as the host and carboxypyridinium salt as the guest.Single-crystal structural analysis indicates that the presence of abundant weak interactions in LIFM-HG1 provides a rigid environment for the guest molecule and effectively blocks the external quenchers.Spectral analysis and theoretical calculations confirm the presence of robust triplet energy levels in LIFM-HG1.Even more impressively,the intersystem crossing channels of the guest molecules are greatly opened up after the formation of the crystalline host-guest aggregate,resulting in a large k_(isc)of 6.70×10^(7)s^(−1)at room temperature for LIFM-HG1(which is∼0 for pure guest),leading to fascinatingmultichannel(including one-photon,two-photon,and X-ray)excited LPL properties.In addition,the crystalline LIFM-HG1 has a much higher triplet state luminescence efficiency under X-ray and two-photon excitation than that under single-photon excitation(A_(P)/A_(F)=86.8,44.8,10.7 under the three circumstances,respectively).And the phosphorescent emission intensity of LIFM-HG1 is 27.6 times higher than that of the crystalline guest under X-ray excitation.As a result,LIFM-HG1 shows a long afterglow retention time under both single-and two-photon excitation,and an impressive afterglow retention time of 1 s under X-ray excitation.Furthermore,the excellent lysosomal targeting and low cytotoxicity by the formation of host-guest aggregate makes LIFM-HG1 promising to be used as a novel lysosomal-targeted two-photon excited phosphorescent tracer.

Preparation of Gd_2O_2S:Pr Scintillation Ceramics by Pressureless Reaction Sintering Method

Fabrication of Gd2O2S：Pr scintillation ceramics by 2Gd2O3.（Gd,Pr）2（SO4）3.mH2O precursor was made Gd2O3, Pr6O11 and H2SO4 as the starting materials pressureless reaction sintering was investigated. The by hydrothermal reaction using commercially available Then single phase Gd2O2SO4：Pr powder was obtained by calcining the precursor at 750℃ for 2 h. The Gd2O2SO4：Pr powder compacts can be sintered to single phase Gd2O2S：Pr ceramics with a relative density of 99% and mean grain size of 30um at 1750℃ for 2 h in flowing hydrogen atmosphere. Densification and microstructural development of the Gd2O2S：Pr ceramics were examined. Luminescence spectra of the Gd2O2S：Pr ceramic under 309 nm UV excitation and X-ray excitation show a green emission at 511 nm as the most prominent peak, which corresponds to the ^3p0-3H4 transition of Pr^3＋ ions.

Enhancing light yield of Tb^(3+)-doped fluoride nanoscintillator with restricted positive hysteresis for low-dose high-resolution X-ray imaging

Developing scintillators with high light yield(LY),superior irradiation stability,and weak afterglow is of significance for the realization of low-dose high-resolution X-ray excited optical luminescence(XEOL)imaging.Lanthanide doped fluoride nanoparticles possess low toxicity,superior environmental stability,facial fabrication process,and tunable emissions,which are appropriate candidates for the next generation nanoscintillators(NSs).However,the low LY and strong positive hysteresis greatly restrict their practical application.Here,we propose an effective strategy that engineers energy gap to significantly enhance the LY.Our results verify that the tetragonal LiLuF4 host benefits the crystal level splitting of Tb^(3+)ions,which greatly promotes the electrons population on the Tb^(3+):5D4 level followed by the enhanced LY.The LY of LiLuF4:Tb@LiLuF4 NSs is calculated to be~31,169 photons/MeV,which is much higher than the lead halide perovskite colloidal CsPbBr3(~21,000 photons/MeV)and LuAG:Ce(~22,000 photons/MeV)scintillators.Moreover,the positive hysteresis is remarkably restricted after coating a thin shell.The X-ray detection limit and spatial resolution are measured to be~21.27 nGy/s and~7.2 lp/mm,respectively.We further verify that this core/shell NS can be employed as scintillating screen to realize XEOL imaging under the low dose rate of 13.86μGy/s.Our results provide an effective route to develop high performance NSs,which will promote great opportunities for the development of low-dose high-resolution XEOL imaging devices.

掺Fe铝酸锂晶体的光谱性能研究

采用提拉法生长了质量较高的掺Fe铝酸锂(LiAlO2:Fe)晶体,并用吸收光谱、光致激发与发射光谱以及X射线激发发射(XEL)光谱测试等方法对晶体的光谱性质及结构进行了研究。结果表明,晶体对可见光与近红外光具有较高的透过,而在深紫外波段存在与Fe离子相关的吸收。以266nm光激发得到710nm的Fe3+离子的特征发射峰,分析表明晶体中Fe3+离子代替Li+离子而处于8面体格位。比较不同晶体样品的XEL光谱发现,空气退火后的γ-LiAlO2晶体出现了318nm处较强的缺陷发光,而同样条件退火后的LiAlO2:Fe晶体与未退火的γ-LiAlO2晶体均未观察到相应的发光。分析得出此发光应与晶体退火后形成的F+心有关,而Fe掺杂可抑制晶体中Li2O的挥发,提高晶体的热稳定性。

Effects of substitution of BaF_2 for GdF_3 on optical properties of dense oxyfluoride borogermanate scintillating glasses

Eu3＋-activated B2O3-GeO2-37Gd2O3-3Eu2O3-（15-x）GdF3-xBaF2 （0≤x≤15） scintillating glasses with the density of 6.1-6.3 g/cm3 were synthesized by a melt-quenching method. The substitution of BaF2 for expensive GdF3 in oxyfluoride borogermanate glasses slightly decreased the glass density within 3.0%. Their optical properties were characterized by transmittance, photolumines- cence （excitation and emission）, and X-ray excited luminescence （XEL） spectra in detail. The emission intensity of Eu3＋ ions increased with the elevated x values. The Eu-O covalancey nature and the local environment of Eu3＋ ions were evaluated by Judd-Ofelt results. It was found that the covalency property of Eu-O bond increased with increasing x values.

Influence of CeO_2 on scintillating properties of Tb^(3+)-doped silicate glasses

A series of Tb3+-,Ce3+-doped,and Tb3+/Ce3+-codoped silicate glasses were synthesized by melt-quenching technique.Some properties of the investigated glasses were characterized by X-ray photoelectron spectroscopy(XPS),photoluminescence(PL),X-ray excited luminescence(XEL) and thermoluminescence(TL) spectra.The result of XPS revealed that both Ce3+ and Ce4+ ions coexisted in these silicate glasses,and energy transfer from Ce3+ to Tb3+ ions was observed under UV excitation.However,under X-ray excitation the XEL...

Novel phosphors of Eu^(3+), Tb^(3+) or Tm^(3+) activated LaBGeO_5

Rare earth borogermanates as a group of stable compounds provided various potential properties important for modern sciences. Among the properties of interests, luminescence was manifested due to the variability of rare earth elements and the compounds constituted an important group of potential candidate. In this work, novel phosphors of Eu3＋, Tb3＋ or Tm3＋ doped LaBGeO5 with the stillwellite type structure were synthesized by the solid state reaction method. Their X-ray and UV excitation luminescent properties showed that LaBGeO5 was an excellent host lattice for the luminescence of Eu3＋, Tb3＋ and Tm3＋. The LaBGeO5：Eu3＋, LaBGeO5：Tb3＋ and LaBGeO5：Tm3＋ presented bright red, green and blue emission light for both UV and X-ray excitation.