Precise Monitoring and Assessing Treatment Response of Sepsis-Induced Acute Lung Hypoxia with a Nitroreductase-Activated Golgi-Targetable Fluorescent Probe.

Sepsis-induced acute lung injury (ALI) is mostly attributed to an outbreak of reactive oxygen species (ROS), which makes leukocytes infiltrate into the lung and results in lung hypoxia. Nitroreductase (NTR) is significantly upregulated under hypoxia, which is commonly regarded as a potential biomarker for assessing sepsis-induced acute lung hypoxia. Increasing evidence shows that NTR in the Golgi apparatus could be induced in sepsis-induced ALI. Meanwhile, the prolyl hydroxylase (PHD) inhibitor (dimethyloxalylglycine, DMOG) attenuated sepsis-induced ALI through further increasing the level of Golgi NTR by improving hypoxia inducible factor-1α (HIF-1α) activity, but as yet, no Golgi-targetable probe has been developed for monitoring and assessing treatment response of sepsis-induced ALI. Herein, we report a Golgi-targetable probe, Gol-NTR, for monitoring and assessing treatment response of sepsis-induced ALI through mapping the generation of NTR. The probe displayed high sensitivity with a low detection limit of 54.8 ng/mL and good selectivity to NTR. In addition, due to the excellent characteristics of Golgi-targetable, Gol-NTR was successfully applied in mapping the change of Golgi NTR in cells and zebrafish caused by various stimuli. Most importantly, the production of Golgi NTR in the sepsis-induced ALI and the PHD inhibitor (DMOG) against sepsis-induced ALI were visualized and precisely assessed for the first time with the assistance of Gol-NTR. The results demonstrated the practicability of Gol-NTR for the precise monitoring and assessing of the personalized treatment response of sepsis-induced ALI.

Emergence of a Radical-Stabilizing Metal-Organic Framework as a Radio-photoluminescence Dosimeter.

Radio-photoluminescence (RPL) materials display a distinct radiation-induced permanent luminescence center, and therefore find application in the detection of ionizing radiation. The current inventory of RPL materials, which were discovered by serendipity, has been limited to a small number of metal-ion-doped inorganic materials. Here we document the RPL of a metal-organic framework (MOF) for the first time: X-ray induced free radicals are accumulated on the organic linker and are subsequently stabilized in the conjugated fragment in the structure, while the metal center acts as the X-ray attenuator. These radicals afford new emission features in both UV-excited and X-ray excited luminescence spectra, making it possible to establish linear relationships between the radiation dose and the normalized intensity of the new emission feature. The MOF-based RPL materials exhibit advantages in terms of the dose detection range, reusability, emission stability, and energy threshold. Based on a comprehensive electronic structure and energy diagram study, the rational design and a substantial expansion of candidate RPL materials can be anticipated.

Gleaming Uranium: An Emerging Emitter for Building X-ray Scintillators.

Scintillators are a unique class of luminescent materials with specific applications towards radiation detection. The emitters within state-of-the-art scintillators are mostly limited to bismuth, cerium, europium, thallium, lead, tungsten, etc. A shared feature of these elements is the relatively high atomic number, which is responsible for high radiation stopping power and radiation-induced luminescence. Searching for new scintillating materials is an essential target aiming at specific applications. In this Concept article, we will discuss our recent works on the topic of "uranyl-bearing scintillators". As a virgin territory in this field, uranyl-bearing scintillators show intrinsic merits for designing new materials with X-ray detection capability, that is, the large photoelectric cross-section, high X-ray attenuation efficiency, and high crystal density. In addition, we also present challenges in the further development of the uranyl-bearing scintillators.

Photo-exfoliation of a highly photo-responsive two-dimensional metal-organic framework.

When exposed to UV (365 nm, 2 mW) radiation, the bulk crystals of a two-dimensional metal-organic framework [Hphen]2[(UO2)2(ox)3] (1,phen = 1,10-phenanthroline, ox = oxalate) are exfoliated into thin sheets (2 µm) and its photoluminescence can be quenched in an incredibly sensitive manner, setting 1 as a superior UV-detection material. When upgrading the UV source into a 300 W xenon light source, the crystals of 1 can be further exfoliated into monolayer nanosheets (0.92 nm).

Inorganic X-ray Scintillators Based on a Previously Unnoticed but Intrinsically Advantageous Metal Center.

Traditional inorganic X-ray scintillators are designed based on several representative metal ions (e.g., Tl+, Pb2+, Bi3+) with highly emissive nature and high atomic number aiming at the outstanding radiation stopping power. The combination of these two features gives rise to a high energy conversion efficiency from X-ray to visible emission, which is a prerequisite for an ideal scintillator and is currently one of the major limits for the further development of this field. Inspired by our recent observation on the intrinsic scintillating phenomenon in the heaviest naturally occurring element uranium, we report here a family of inorganic scintillators through combination of uranyl ions with diverse oxoanion groups (i.e., borate, phosphate, molybdate, germanate, etc.). Na2UO2(MoO4)2·(H2O) (UMO) is selected as a prototype of a uranyl-bearing inorganic scintillator, to show its intrinsic advantages in the X-ray excited luminescence (XEL), strong X-ray attenuation coefficient (XAC), reduced afterglow, and decent radiation stability, as compared with one of the most important commercial inorganic scintillators CsI:Tl.

Monitoring Ultraviolet Radiation Dosage Based on a Luminescent Lanthanide Metal-Organic Framework.

A luminescent lanthanide metal-organic framework [Tb7(OH)8(H2O)6(IDA)3(COO)3]·4Cl·2H2O (Tb-IDA, IDA = iminodiacetic acid) was hydrothermally synthesized and structurally characterized. Monitoring ultraviolet radiation was achieved by correlating the dosage with the luminescence color change in doped Gd99Tb0.1Eu0.9-IDA compound. A linear relationship is developed across a broad range from blue to yellow within a CIE chromaticity diagram.

Emergence of Uranium as a Distinct Metal Center for Building Intrinsic X-ray Scintillators.

The combination of high atomic number and high oxidation state in UVI materials gives rise to both high X-ray attenuation efficiency and intense green luminescence originating from ligand-to-metal charge transfer. These two features suggest that UVI materials might act as superior X-ray scintillators, but this postulate has remained substantially untested. Now the first observation of intense X-ray scintillation in a uranyl-organic framework (SCU-9) that is observable by the naked eye is reported. Combining the advantage in minimizing the non-radiative relaxation during the X-ray excitation process over those of inorganic salts of uranium, SCU-9 exhibits a very efficient X-ray to green light luminescence conversion. The luminescence intensity shows an essentially linear correlation with the received X-ray intensity, and is comparable with that of commercially available CsI:Tl. SCU-9 possesses an improved X-ray attenuation efficiency (E>20 keV) as well as enhanced radiation resistance and decreased hygroscopy compared to CsI:Tl.

Facile and Efficient Decontamination of Thorium from Rare Earths Based on Selective Selenite Crystallization.

The coexistence of radioactive contaminants (e.g., thorium, uranium, and their daughters) in rare earth minerals introduces significant environmental, economic, and technological hurdles in modern rare earth production. Efficient, low cost, and green decontamination strategies are therefore desired to ameliorate this problem. We report here a single-step and quantitative decontamination strategy of thorium from rare earths based on a unique periodic trend in the formation of crystalline selenite compounds across the lanthanide series, where Ce(III) is fully oxidized in situ to Ce(IV). This gives rise to a crystallization system that is highly selective to trap tetravalent f-blocks while all other trivalent lanthanides completely remain in solution when coexist. These results are bolstered by first-principles calculations of lattice energies and an examination of bonding in these compounds. This system is contrasted with typical natural and synthetic systems, where trivalent and tetravalent f-block elements often cocrystallize. The separation factors after one round of crystallization were determined from binary systems of Th(IV)/La(III), Th(IV)/Eu(III), and Th(IV)/Yb(III) to reach 2.1 × 105, 1.2 × 105, and 9 × 104, respectively. Selective crystallization of thorium from a simulated monazite composite yields a separation factor of 1.9 × 103 with nearly quantitative removal of thorium.

Tunable 4f/5f Bimodal Emission in Europium-Incorporated Uranyl Coordination Polymers.

There have been numerous studies on emission-color regulation by the adjustment of molar amounts of multiple trivalent lanthanide cations, such as Eu3+, Tb3+, Dy3+, and others, in many types of solid host materials. Although uranyl emission originating from charge-transfer transitions has been well-recognized and investigated for many decades, as of now there is no report on tunable 4f/5f bimodal emission based on heterobimetallic lanthanide(III) and uranyl(VI) compounds. In most cases, complete energy transfer between uranyl(VI) and lanthanide(III) centers was observed. In this work, a series of isotypic-europium-incorporated uranyl coordination polymers, Eu@UO2L(DMF) (L2- = 3,5-pyridinedicarboxylate, denoted as 1-10, which represent the different Eu contents in UO2L(DMF); DMF = N,N-dimethylformamide), has been synthesized by solvothermal reactions. Crystallographic evidence of this series unveiled one-dimensional chains of UO22+ as pentagonal-bipyramidal units bridged by pyridinedicarboxylate with no defined, crystallographically unique site containing Eu, even for the products with high concentrations of Eu in this series. However, emission bands characteristic of Eu3+ were clearly observed in every product along with the characteristic uranyl-emission feature when observed with UV-vis fluorescence spectroscopy. Laser-ablation inductively coupled plasma mass spectrometry indicated that europium was concomitant with uranium, corroborating the incorporation of europium into crystals of UO2L(DMF). Systematic control of the solvent ratio (VH2O/VDMF) in each reaction gives rise to an enrichment of Eu3+ in the interior of UO2L(DMF). In addition, the color of emission of these compounds changed significantly from bright red to bright green with decreasing Eu content. This phenomenon occurs from the highly efficient energy transfer between the UO22+ and Eu3+ centers within each sample, providing the first case of a tunable 4f/5f bimodal emission in a mixed 4f/5f-elements-bearing metal-organic-hybrid material.

Mild Periodic Acid Flux and Hydrothermal Methods for the Synthesis of Crystalline f-Element-Bearing Iodate Compounds.

f-element-bearing iodate compounds are a large family mostly synthesized by hydrothermal reactions starting with actinide/lanthanide ions and iodic acid or iodate salt. In this work, we introduce melting periodic acid flux as a new reaction medium and provide a safe way for single-crystal growth of a series of new f-element iodate compounds including UO2(IO3)2·H2O (1), UO2(IO3)2(H2O)·HIO3 (2), α-Th(IO3)2(NO3)(OH) (3), ß-Th(IO3)2(NO3)(OH) (4), and (H3O)9Nd9(IO3)36·3HIO3 (5). The structures of these compounds deviate from those afforded from hydrothermal reactions. Specifically, compounds 1 and 2 exhibit pillared structures consisting of uranyl pentagonal bipyramids and iodate trigonal pyramids. Compounds 3 and 4 represent two new thorium iodate compounds that are constructed from subunits of thorium dimers. Compound 5 exhibits a flower-shaped trivalent lanthanide iodate structure with HIO3 molecules and H3O+ cations filled in the channels. The aliovalent replacement of f elements in 5 is available from a hydrothermal process, further generating compounds of Th2(IO3)8(H2O) (6) and Ce2(IO3)8(H2O) (7). The distinct absorption features are observed in isotypic compounds 5-7, where 7 shows typical semiconductor behavior with a band gap of 2.43 eV. Remarkably, noncentrosymmetric 1, 6, and 7 exhibit strong second-harmonic-generation efficiencies of 1.3, 3.2, and 9.2 times, respectively, that of the commercial material KH2PO4. Additionally, the temperature-dependent emission spectra of 1 and 2 were also collected showing typical emission features of uranyl units and a negative correlation between the intensities of the emissions with temperature. Clearly, the presented low-temperature melting inorganic acid flux synthesis would provide a facile and effective strategy to produce a large new family of structurally versatile and multifunctional f-element inorganic compounds.

Highly Sensitive Detection of Ionizing Radiations by a Photoluminescent Uranyl Organic Framework.

Precise detection of low-dose X- and γ-radiations remains a challenge and is particularly important for studying biological effects under low-dose ionizing radiation, safety control in medical radiation treatment, survey of environmental radiation background, and monitoring cosmic radiations. We report here a photoluminescent uranium organic framework, whose photoluminescence intensity can be accurately correlated with the exposure dose of X- or γ-radiations. This allows for precise and instant detection of ionizing radiations down to the level of 10-4  Gy, representing a significant improvement on the detection limit of approximately two orders of magnitude, compared to other chemical dosimeters reported up to now. The electron paramagnetic resonance analysis suggests that with the exposure to radiations, the carbonyl double bonds break affording oxo-radicals that can be stabilized within the conjugated uranium oxalate-carboxylate sheet. This gives rise to a substantially enhanced equatorial bonding of the uranyl(VI) ions as elucidated by the single-crystal structure of the γ-ray irradiated material, and subsequently leads to a very effective photoluminescence quenching through phonon-assisted relaxation. The quenched sample can be easily recovered by heating, enabling recycled detection for multiple runs.

Substitutional Disorder of SeO32-/IO3- in the Crystalline Solid Matrix: Insights into the Fate of Radionuclides 79Se and 129I in the Environment.

As the crucial soluble species of long-lived radionuclides 129I and 79Se, iodate and selenite anions commonly share similar geometry of the trigonal pyramid XO3 (X = I, Se) but in different valence states. Although large amounts of investigations have been performed aiming at understanding the environmental behavior of these two anions individually, studies on cases when they coexist are extremely scarce. Structurally well-characterized natural/synthetic crystalline solids simultaneously incorporating these two anions as potential solubility-limiting products at the nuclear waste geological depository remain elusive. We report here a crystalline solid Th(IO3)2(SeO3) representing the first example of aliovalent substitution between IO3- and SeO32- sharing the same structural site, as demonstrated by single crystal X-ray diffraction, laser-ablation inductively coupled plasma mass spectrometry analysis, and spectroscopic techniques including infrared, Raman, and X-ray absorption spectroscopies. Sequentially, in the Eu(IO3)3 solid matrix, we demonstrated that the IO3- site can be sufficiently substituted by SeO32- in the presence of Th4+ via simultaneous incorporation of Th4+ and SeO32- in a charge-balancing mechanism. The obtained results provide insights into the environmental behavior of fission products 79Se and 129I: they may cocrystallize in one solid matrix and may be efficiently immobilized by incorporation into each other's solid phase through solid solution.

Rare earth separations by selective borate crystallization.

Lanthanides possess similar chemical properties rendering their separation from one another a challenge of fundamental chemical and global importance given their incorporation into many advanced technologies. New separation strategies combining green chemistry with low cost and high efficiency remain highly desirable. We demonstrate that the subtle bonding differences among trivalent lanthanides can be amplified during the crystallization of borates, providing chemical recognition of specific lanthanides that originates from Ln3+ coordination alterations, borate polymerization diversity and soft ligand coordination selectivity. Six distinct phases are obtained under identical reaction conditions across lanthanide series, further leading to an efficient and cost-effective separation strategy via selective crystallization. As proof of concept, Nd/Sm and Nd/Dy are used as binary models to demonstrate solid/aqueous and solid/solid separation processes. Controlling the reaction kinetics gives rise to enhanced separation efficiency of Nd/Sm system and a one-step quantitative separation of Nd/Dy with the aid of selective density-based flotation.

Boosting Proton Conductivity in Highly Robust 3D Inorganic Cationic Extended Frameworks through Ion Exchange with Dihydrogen Phosphate Anions.

The limited long-term hydrolytic stability of rapidly emerging 3D-extended framework materials (MOFs, COFs, MOPs, etc.) is still one of major barriers for their practical applications as new solid-state electrolytes in fuel cells. To obtain hydrolytically stable materials, two H2 PO4 (-) -exchanged 3D inorganic cationic extended frameworks (CEFs) were successfully prepared by a facile anion-exchange method. Both anion-exchanged CEFs (YbO(OH)P and NDTBP) show significantly enhanced proton conductivity when compared with the original materials (YbO(OH)Cl and NDTB) with an increase of up to four orders-of-magnitude, reaching 2.36×10(-3) and 1.96×10(-2)  S cm(-1) at 98 % RH and 85 °C for YbO(OH)P and NDTBP, respectively. These values are comparable to the most efficient proton-conducting MOFs. In addition, these two anion-exchanged materials are stable in boiling water, which originates from the strong electrostatic interaction between the H2 PO4 (-) anion and the cationic host framework, showing a clear advance over all the acid-impregnated materials (H2 SO4 @MIL-101, H3 PO4 @MIL-101, and H3 PO4 @Tp-Azo) as practical solid-state fuel-cell electrolytes. This work offers a new general and efficient approach to functionalize 3D-extended frameworks through an anion-exchange process and achieves water-stability with ultra-high proton conductivity above 10(-2)  S cm(-1) .

Unravelling the Proton Conduction Mechanism from Room Temperature to 553 K in a 3D Inorganic Coordination Framework.

The preparation of proton-conducting materials that are functional and stable at intermediate temperatures (393-573 K) is a focal point of fuel cell development. The purely inorganic material, HNd(IO3)4, which possesses a dense 3D framework structure, can reach a maximum of 4.6 × 10(-4) S·cm(-1) at 353 K and 95% relative humidity and exhibit a high conductivity of 8.0 × 10(-5) S·cm(-1) from 373 to 553 K under the flow of wet N2. HNd(IO3)4 exhibits a variety of improvements including high thermal stability, low solubility in water, and resistance to reducing atmosphere. The proton conductivity in such a wide temperature range originates from the intrinsic liberated protons in the structure and the resulting 1D hydrogen-bonding network confirmed by bond valence sum calculation and solid-state NMR analysis. Moreover, two different activation energies are observed in different temperature regions (0.23 eV below 373 K and 0.026 eV from 373 to 553 K), indicating that two types of proton motion are responsible for proton diffusion, as further domenstrated by temperature-dependent open-circuit voltage hysteresis in a tested fuel cell assembly as well as variable-temperature and double quantum filtered solid-state NMR measurements.

Insertion of Trivalent Lanthanides into Uranyl Vanadate Layers and Frameworks.

Two new uranyl vanadates have been prepared from hydrothermal reactions and structurally characterized by single-crystal X-ray diffraction. The structure of (H3O)UO2VO4 (UVO-1) consists of anionic layers containing UO2(2+) pentagonal bipyramids coordinated by edge-sharing VO5 square pyramids, with the charge balanced by interlaminar H3O(+) cations. Vanadium in (UO2)3(VO4)2(H2O)3 (UVO-2) exists as monomeric VO4 tetrahedra coordinating to UO2(2+) pentagonal bipyramids, forming a 3D uranyl(VI) vanadate framework. Similar reactions with the addition of Ln(NO3)3 (Ln = Nd, Eu) afford the three heterobimetallic lanthanide uranyl vanadate frameworks Nd(UO2)3(VO4)3(H2O)11 (NdUVO-1), Eu(UO2)3(VO4)3(H2O)10 (EuUVO-1), and Eu2(UO2)12(VO4)10(H2O)24 (EuUVO-2). In NdUVO-1 and EuUVO-1, Ln(3+) cations are inserted into the interlayer space of UVO-1 substituting for H3O(+) and further bridging adjacent layers into 3D frameworks. Similarly, EuUVO-2 adopts the same sheet topology as UVO-2, with Eu(3+) ions replacing some of the interlayer uranyl ions in UVO-2. Our work has demonstrated that uranyl vanadate extended structures are excellent hosts for further incorporation of trivalent lanthanide/actinide cations and has provided a new way to create new heterobimetallic 4f-5f and 5f-5f compounds.