Charge Transport and Photoconductivity in a Hybrid Uranium(IV) Halide Perovskite.

Hybrid metal halide perovskites are extensively synthesized using p- and d-elements. However, the properties of hybrid halide perovskites involving 5f-elements are still elusive. Herein, we first report the semiconductive property of a uranium-bearing hybrid halide perovskite, [N(C2H5)4]2UCl6 (EAUCl). Single crystal X-ray crystallography demonstrates that EAUCl adopts a zero-dimensional molecular structure consisting of isolated [UCl6]2- anions and organic cations. The intrinsically semiconductive property endows EAUCl with obvious charge transport and photoconductivity, with a high carrier mobility lifetime (µτ) product of 9.91 × 10-4 cm2/V and a photocurrent on-off ratio of 380 under X-ray excitation. Theoretical calculations corroborate that the U 5f orbitals are involved in electron transitions and the formation of band structure.

Selective Extraction and Complexation Studies for Thorium(IV) with Bis-triamide Extractants: Synthesis, Solvent Extraction, EXAFS, and DFT.

Three octyl-extended bis-triamide extractants (L1-L3) were designed and synthesized for the selective solvent extraction of Th(IV) over U(VI) in a kerosene-HNO3 system. L1 and L2 exhibited good extraction property and selectivity toward Th(IV) over U(VI) and reached extraction equilibrium within 10 min. In a wide range of a HNO3 concentration from 0.1 to 3.0 M, the separation factor of Th(IV) over U(VI) (SFTh/U) of L1 and L2 ranged from 12.1 ± 1.6 to 123.0 ± 20.2 and 15.2 ± 2.4 to 88.1 ± 14.9, respectively. Slope analysis indicated that Th(IV) was extracted as different species under different HNO3 concentrations, in which the slopes were 2.08 ± 0.20, 1.61 ± 0.03, and 1.54 ± 0.03 for L1 and 2.37 ± 0.22, 2.07 ± 0.17, and 1.76 ± 0.18 for L2 under 0.1, 1.0, and 3.0 M HNO3, respectively. A continuous variation method (Job plot) illustrated a 1.5:1 ligand/thorium (L/Th) ratio in a methanol phase, indicating that L1/L2 and Th(IV) could form mixed 1:1 and 2:1 L/Th extracted complexes. Extended X-ray absorption fine structure (EXAFS) and density functional theory (DFT) calculations revealed that the extracted complexes of L1 and L2 with Th during the extraction process at 0.1 M HNO3 were [2L1·Th·3(NO3)]+ and [2L2·Th·3(NO3)]+.

Construction of Flexible Amine-linked Covalent Organic Frameworks by Catalysis and Reduction of Formic Acid via the Eschweiler-Clarke Reaction.

Compared to the current mainstream rigid covalent organic frameworks (COFs) linked by imine bonds, flexible COFs have certain advantages of elasticity and self-adaptability, but their construction and application are greatly limited by the complexity in synthesis and difficulty in obtaining regular structure. Herein, we reported for the first time a series of flexible amine-linked COFs with high crystallinity synthesized by formic acid with unique catalytic and reductive bifunctional properties, rather than acetic acid, the most common catalyst for COF synthesis. The reaction mechanism was demonstrated to be a synchronous in situ reduction during the formation of imine bond. The flexibilities of the products endow them with accommodative adaptability to guest molecules, thus increasing the adsorption capacities for nitrogen and iodine by 27 % and 22 %, respectively. Impressively, a novel concept of flexibilization degree was proposed firstly, which provides an effective approach to rationally measure the flexibility of COFs.

Noncomplexed Cucurbituril-Mediated Structural Evolution of Layered Uranyl Terephthalate Compounds.

Template synthesis is one of the most feasible ways to explore new uranyl compounds with intriguing structures and properties. Here we demonstrate the preparation of six novel "sandwichlike" uranyl coordination polymers (UCPs) based on two-dimensional uranyl-terephthalate acid (H2TP) networks using CBn (n = 5, 6, 8) as template ligands in the presence of different cations (Na+, K+, Cs+, or H2N(CH3)2+). Compound 1 ([UO2(TP)2][Na2(CB5)(H2O)](H2O)5) is composed of layered uranyl-TP networks with the complex of CB5 and sodium cations as template ligands. In compound 2 ([(UO2)2(TP)3]2(CB6)(H2O)10), CB6 located between uranyl-TP networks contacts them by π-π interactions and hydrogen bonds. Compound 3 ([(UO2)2(TP)3]2[Na2(H2O)10(CB6)]) is the same as compound 2 except for sodium cations bonding with CB6. Similarly in compound 4 ([(UO2)2(TP)3][Cs(H2O)3(CB6)]), CB6 is a capsulelike structure capped with two cesium cations and interacts with uranyl-TP networks through π-π and C-H···π interactions. Compound 5 ([(UO2)2(TP)3(HCOO)2][K(H2O)2(CB5)]2[H2N(CH3)2]2(CB6)(H2O)6) consists of both templates of CB6 and CB5 in which each CB5 is capped with one potassium cation while the H2N(CH3)2+ cation is held at CB6 portals. In compound 6 ([(UO2)2(TP)3]2[UO2(TP)2(H2O)2][Cs(CB8)3(H2O)4](H2O)16), CB8 ligands are connected by cesium cations to form a triangle motif and are further located between the uranyl-TP networks as template agents. All of the 2D layered structures with free CBn or cation-anchored CBn intercalate into the laminates of uranyl-terephthalate and shows a cucurbituril-mediated structural evolution. The regulating role of CBn as structure-directing template agents for the construction of layered UCPs through outer-surface interactions with layers of uranyl terephthalate is demonstrated, especially for the case of CB6 with contractive interlayer spacing.

Molecular Spring-like Triple-Helix Coordination Polymers as Dual-Stress and Thermally Responsive Crystalline Metal-Organic Materials.

Elastic metal-organic materials (MOMs) capable of multiple stimuli-responsiveness based on dual-stress and thermally responsive triple-helix coordination polymers are presented. The strong metal-coordination linkage and the flexibility of organic linkers in these MOMs, rather than the 4 Šstacking interactions observed in organic crystals, causes the helical chain to act like a molecular spring and thus accounts for their macroscopic elasticity. The thermosalient effect of elastic MOMs is reported for the first time. Crystal structure analyses at different temperatures reveal that this thermoresponsiveness is achieved by adaptive regulation of the triple-helix chains by fine-tuning the opening angle of flexible V-shaped organic linkers and rotation of its lateral conjugated groups to resist possible expansion, thus demonstrating the vital role of adaptive reorganization of triple-helix metal-organic chains as a molecular spring-like motif in crystal jumping.

Bipyridine-Directed Syntheses of Uranyl Compounds Containing Semirigid Dicarboxylate Linkers: Diversity and Consistency in Uranyl Speciation.

Bipyridine organic bases are beneficial to the synthesis of novel uranyl-organic hybrid materials, but the relationship between their molecular structures and specific roles as structure-directing agents, especially for the semirigid dicarboxylate systems, is still unclear. Here we demonstrate how the bipyridine ligands direct the coordination assembly of uranyl-organic compounds with a semirigid dicarboxylate linker, 4,4'-dicarboxybiphenyl sulfone (H2dbsf), by utilizing a series of bipyridine ligands, 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bpy), 5,5'-dimethylbipyridine (5,5'-dmbpy), 4,4'-bipyridine (4,4'-bpy), or 1,3-di(4-pyridyl)propane (bpp). Under hydrothermal conditions, eight uranyl-organic coordination polymers (UCPs), four of which [[UO2(dbsf)(phen)] (1), [UO2(dbsf)(phen)]·H2O (1'), [U4O10(dbsf)3]2[H2bpp]2 (6), and [U4O10(dbsf)3]2[H2bpp] (6')] were reported previously, were synthesized and divided into two types based on the chelate or template effect of these bipyridine ligands. 1, 1', [UO2(dbsf)(2,2'-bpy)] (2), and [(UO2)2(dbsf)2(5,5'-dmbpy)2] (3) are springlike triple helices with bipyridine ligands (phen, 2,2'-bpy, or 5,5'-dmbpy) as chelate ligands, while [U4O10(dbsf)3][H2(4,4'-bpy)] (4), [U4O10(dbsf)3]2[H(4,4'-bpy)]2[Ni(H2O)6] (5), 6, and 6' are tetranuclear uranyl-mediated 2-fold-interpenetrating networks with 4,4'-bpy or bpp as template ligands and charge-balancing agents. The participation or not in uranyl coordination of different bipyridine ligands promotes not only diversity in uranyl speciation and final topological structures among different classes of organic bases but also consistency for the same types of bipyridine ligands, which thus endows the possibility of the rational design of UCPs based on semirigid dicarboxylate ligands with the aid of cautiously selected bipyridine ligands.

68Ga/177Lu-labeled DOTA-TATE shows similar imaging and biodistribution in neuroendocrine tumor model.

Somatostatin receptors are overexpressed in neuroendocrine tumors, whose endogenous ligands are somatostatin. DOTA-TATE is an analogue of somatostatin, which shows high binding affinity to somatostatin receptors. We aim to evaluate the 68Ga/177Lu-labeling DOTA-TATE kit in neuroendocrine tumor model for molecular imaging and to try human-positron emission tomography/computed tomography imaging of 68Ga-DOTA-TATE in neuroendocrine tumor patients. DOTA-TATE kits were formulated and radiolabeled with 68Ga/177Lu for 68Ga/177Lu-DOTA-TATE (M-DOTA-TATE). In vitro and in vivo stability of 177Lu-DOTA-TATE were performed. Nude mice bearing human tumors were injected with 68Ga-DOTA-TATE or 177Lu-DOTA-TATE for micro-positron emission tomography and micro-single-photon emission computed tomography/computed tomography imaging separately, and clinical positron emission tomography/computed tomography images of 68Ga-DOTA-TATE were obtained at 1 h post-intravenous injection from patients with neuroendocrine tumors. Micro-positron emission tomography and micro-single-photon emission computed tomography/computed tomography imaging of 68Ga-DOTA-TATE and 177Lu-DOTA-TATE both showed clear tumor uptake which could be blocked by excess DOTA-TATE. In addition, 68Ga-DOTA-TATE-positron emission tomography/computed tomography imaging in neuroendocrine tumor patients could show primary and metastatic lesions. 68Ga-DOTA-TATE and 177Lu-DOTA-TATE could accumulate in tumors in animal models, paving the way for better clinical peptide receptor radionuclide therapy for neuroendocrine tumor patients in Asian population.

Supramolecular Isomers of Coordination-Directed Side-Chain Polypseudorotaxanes Based on Trimeric Uranyl Oxalate Nodes.

Although the prosperity of rotaxane coordination polymers with rotaxane molecules serving as main-chain linkers is known, side-chain metal-organic polypseudorotaxanes incorporating macrocyclic host molecules have not been reported to date. Herein a new type of coordination-driven cucurbit[6]uril-bearing side-chain polypseudorotaxane, with two-dimensional trimeric uranyl-oxalate as main chains, has been synthesized. This was carried out through hydrothermal reactions of uranyl components with an in situ-formed carboxylated pseudorotaxane ligand in the presence of oxalate co-ligands. Varying the substitution site of coordination groups led to two different supramolecular isomers. Further mechanistic analysis indicated that condition-dependent hydrolysis of the cyano groups of the pseudorotaxane ligand, as well as the participation of oxalate groups into the coordination sphere of uranyl moieties, contributes to the formation of this new type of side-chain polypseudorotaxane.

Establishing Reliable Cu-64 Production Process: From Target Plating to Molecular Specific Tumor Micro-PET Imaging.

Copper-64 is a useful radioisotope for positron emission tomography (PET). Due to the wide range of applications, the demand of 64Cu with low metallic impurities is increasing. Here we report a simple method for the efficient production of high specific activity 64Cu using a cyclotron for biomedical application. We designed new equipment based on the plating of enriched 64Ni as the target, and used automated ion exchange chromatography to purify copper-64 efficiently after irradiation and dissolution of the target in good radiochemical and chemical yield and purity. The 64Cu radionuclide produced using 99.32% enriched 64Ni with a density of 61.4 ± 5.0 mg/cm², reaching a total radioactivity greater than 200 mCi, with specific activity up to 5.6 GBq/µmoL. It was further incorporated into modified monoclonal antibody DOTA-rituximab to synthesize 64Cu-DOTA-rituximab, which was used successfully for micro-PET imaging.

Effects of different metal ions on the fluorescence of CdSe/ZnS quantum dots capped with various thiolate ligands.

In this report, we systematically studied the effects of different metal ions on the fluorescence of common thiolate ligand capped quantum dots. Generally, heavy metal ions exhibited much more significant fluorescence quenching. Also, the coordination capability and steric hindrance of the ligand jointly affect the quenching efficiency.

Purification and separation of single-walled carbon nanotubes (SWCNTs).

Purification or separation of single-walled carbon nanotubes (SWCNTs) is one of the most fundamental steps before they are used for research and technological applications. Based on the difference of their physical and chemical properties, separation of carbon nanotubes (CNTs) can be categorized into three groups: length separation, metallic and semiconducting tubes separation and chirality separation. In this review, we first briefly review the purification of CNTs and then focus on the different methods for the separation of CNTs.

Amide Linkages in Pyrene-Based Covalent Organic Frameworks toward Efficient Photocatalytic Reduction of Uranyl.

The bond linkages in covalent organic frameworks (COFs) partly determine its physical and chemical properties, thus affecting the photoreactive activity by influencing the generation of photoelectrons and the separation of excitons. Herein, pyrene-based amide COF 4,4',4″,4‴-(pyrene-1,3,6,8-tetrayl)tetrabenzaldehyde-3,8-diamino-6-phenylphenanthridine (TFPPy-DP) was synthesized by postsynthetic modification of imine COFs. Due to the introduction of oxygen atoms into the framework and the change in polarity, an increased number of photogenerated electrons and a wide band gap for amide COFs were found, hydrophilicity and dispersibility were prompted as well. Both imine and amide COF TFPPy-DP were applied in the photocatalytic reduction and removal of toxic U(VI) under visible light, the catalytic reduction equilibrium (91% removal percentage of 238 ppm U at pH 3) was achieved by imine COFs with 10 h of irradiation, while amide COFs only took 2 h of irradiation (82% removal percentage). The much faster photocatalytic reduction rate of U(VI) can be attributed to the fact that amide COF TFPPy-DP retained crystallinity and permanent porosity and exhibited lower electrochemical impedance and enhanced charge separation and accumulation. Further electronic excitation analysis based on time-dependent density functional theory calculations revealed that the intramolecular charge-transfer effect in amide TFPPy-DP enhanced its photocatalytic rate.

A semiconducting uranium-organic framework based on a tetrathiafulvalene derivative.

A rare case of semiconducting actinide-based metal-organic framework SCU-125 was designed and synthesized. As a result of the lack of two coordination sites in the plane of the tetrathiafulvalene tetrabenzoate (TTFTB) molecule, a defective kgd network was formed. The electrical conductivity of SCU-125 was measured to be 2.2(2) × 10-7 S cm-1 at 25 °C ± 2 °C.

Visible light driven photocatalytic removal of uranium(VI) in strongly acidic solution.

Photocatalytic reduction and removal of toxic uranium(VI) from aqueous solution is a highly economic, non-pollutant and efficient strategy. However, most uranium containing waste waters are highly acidic, but current photocatalysts are still restricted in slightly acidic or neutral media (pH ≥ 4). Herein, a conjugated microporous polymer (CMP), pTTT-Ben, was used for visible light driven photocatalytic reduction of U(VI) in highly acidic condition (pH = 1). A high uranium removal capacity (4710 mg/g) was achieved. The structural information of reduced uranium was investigated by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS), revealing the amorphous U(IV) hydrate complex, with an additional interaction between U(IV) and nitrogen atoms on pTTT-Ben. In addition, pTTT-Ben also showed excellent photocatalytic U(VI) reduction performance under natural sunlight irradiation.

[Preparation and biological characteristics of a new doxorubicin-gelatin-microspheres for hepatic artery embolization].

OBJECTIVE: To prepare a new doxorubicin-gelatin-microspheres (DR-GMs) suitable for hepatic artery chemoembolization. METHODS: Oxidized dextran and glutaraldehyde were used respectively as crosslinking agent for preparing DR-GMs. Orthogonal design was employed to optimize the preparation of the oxidized dextran cross-linked GMs. The morphology, swelling, and in vitro and in vivo degrading were compared between the two groups of microspheres, both with 60% degree of cross-linking. RESULTS: The granulometers of both groups of microspheres fitted for hepatic artery embolization. The roundness of the microspheres (observed with scanning electron microscope) crosslinked by oxidized-dextran was better than those crosslinked by glutaraldehyde. The microspheres crosslinked by oxidized-dextran had an average diameter of (78.2 +/- 8.1) microm, and a narrow size distribution (76.4 +/- 3.2)%, which ranged from 50 to 125 microm. The drug content rate and encapsulation rate of the microspheres crosslinked by oxidized-dextran were (87.5 +/- 0.9)% and (12.2 +/- 1.1)% respectively, higher than those crosslinked by glutaraldehyde (P < 0.01). The cumulative release rate of doxorubicin from the microspheres crosslinked by oxidized-dextran in 12 hours was 83.2%, lower than that from the microspheres crosslinked by glutaraldehyde (P < 0.01). The in vitro and in vivo studies found that the duration of degradation of the microspheres crosslinked by oxidized-dextran appeared longer than those crosslinked by glutaraldehyde. CONCLUSION: Oxidized-dextran is a better crosslinking agent for preparing DR-GMs, because it has more advantages over glutaraldehyde as for hepatic artery chemoembolization.

Complexation and Separation of Trivalent Actinides and Lanthanides by a Novel DGA Derived from Macrocyclic Crown Ether: Synthesis, Extraction, and Spectroscopic and Density Functional Theory Studies.

A DGA-arm-grafted macrocyclic aza-crown ether ligand (Cr6DGA) was synthesized, and its solvent extraction behavior toward trivalent americium and europium in nitric acid medium was studied. The effects of various parameters such as the contact time, temperature, concentration of the extractant, and acidity on the extraction by Cr6DGA were investigated. It was found that in 3 mol/L HNO3, the SFEu/Am value was about 2. The complexation energies calculated by DFT showed that the Eu(III) complexes were more stable than the corresponding Am(III) complexes in gas, aqueous, and organic phases. Furthermore, the coordination study showed that the metal/ligand ratio of the extracted species was 1:2 by mass spectrometry (MS) analysis. The time-resolved laser-induced fluorescence spectra (TRLFS) further proved that the extracted species contained one water molecule, and so the composition of the extracted complexes may be [EuL2NO3(H2O)]2+ or [EuL2(NO3)2(H2O)]+. Finally, DFT calculations revealed that [EuL2(NO3)2(H2O)]+ is a more stable species and the binding energy of Eu(III) with the DGA unit is lower than that with the crown unit.

Crystalline quantum dots of covalent organic frameworks for fast and sensitive detection of uranium.

A crystalline quantum dot of a COF was prepared for the first time by the original BRB method and a novel pathway for online monitoring of the COF reaction rate was proposed. The quantum dot can respond to uranyl ion quickly and sensitively and is of great potential in uranium detection.

Insights into mechanism on organic acids assisted translocation of uranium in Brassica juncea var. foliosa by EXAFS.

Citric acid (CA) and Lactic acid (LA) were used as additives to study the mechanism of organic acid promoting the root-to-shoot translocation of uranium (U) in Brassica juncea var. foliosa from molecular and tissue levels. Firstly, the distribution of U in plants under the condition of different organic acids concentrations were studied. The accumulation of U in leafs of 1 mM CA group and 5 mM LA group reached 2225 and 1848 mg/kg respectively, which was about 5 times that of the control group. Secondly, the speciation and distribution of U in plant roots after exposure to different culture solutions were studied by EXAFS and SEM. The result of EXAFS found that the complex of U with organic acids resulted in the U accumulated in the roots was the uranyl carboxylate speciation, while the control group only was the uranyl phosphate speciation. SEM results showed that the lactic acids could enhanced the translocation of U from the cortex to the stele. Thirdly, we further studied the apoplastic pathway and the symplastic pathway of U translocation using transpiration inhibitor and metabolism inhibitor. Compared with the control group, it was likely that the complex of U with organic acids were translocated into the shoot of plants through the apoplastic pathway.

Crystal structure of a host-guest complex of the tris-urea receptor, 3-(4-nitro-phen-yl)-1,1-bis-{2-[3-(4-nitro-phen-yl)ureido]eth-yl}urea, that encapsulates hydrogen-bonded chains of di-hydrogen phosphate anions with separate tetra-n-butyl-ammonium counter-ions.

The title compound, C25H25N9O9·C16H36N+·H2PO4 - (I) or (C25H25N9O9)·(n-Bu4N+)·(H2PO4 -) (systematic name: 3-(4-nitro-phen-yl)-1,1-bis-{2-[3-(4-nitro-phen-yl)ureido]eth-yl}urea tetra-butyl-ammonium di-hydrogen phosphate), comprises a tris-urea receptor (R), a di-hydrogen phosphate anion and a tetra-n-butyl-ammonium cation. It crystallizes with two independent formula units in the asymmetric unit. The conformations of the two tris-urea receptors are stabilized by N-H⋯O and C-H⋯O intra-molecular hydrogen bonds. Each di-hydrogen phosphate anion has two O-H⋯O inter-molecular hydrogen-bonding inter-actions with the other di-hydrogen phosphate anion. Inversion-related di-anion units are linked by further O-H⋯O hydrogen bonds, forming a chain propagating along the a-axis direction. Each di-hydrogen phosphate anion makes a total of four N-H⋯O(H2PO4 -) hydrogen bonds with two ureido subunits from two different tris-urea receptors, hence each tris-urea receptor provides the two ureido subunits for the encapsulation of the H2PO4 - hydrogen-bonded chain. There are numerous inter-molecular C-H⋯O hydrogen bonds present involving both receptor mol-ecules and the tetra-n-butyl-ammonium cations, so forming a supra-molecular three-dimensional structure. One of the butyl groups and one of the nitro groups are disordered over two positions of equal occupancy.

Benzotriazole decorated graphene oxide for efficient removal of U(VI).

There is a need to develop highly efficient materials for capturing uranium from nuclear wastewater. Here, 5-methylbenzotriazole modified graphene oxide (MBTA-GO) was used to adsorb U(VI) from aqueous solution. By the trials of different conditions, we found that the removal of U(VI) from acidic solution was strongly dependent on pH but independent of ionic strength. The U(VI) adsorption was perfectly conformed to the pseudo-second-order kinetics and the adsorption isotherms were simulated by the Langmuir model well. A high removal capacity (qmax = 264 mg/g) for U(VI) at pH 3.5 was obtained. XPS, EXAFS analyses and DFT calculations revealed that the mechanism of uranium capture was ascribed to (i) the surface complexation by benzotriazole and carboxyl groups (providing lone pair electrons) on MBTA-GO and (ii) enhanced synergistic coordination ability of delocalized π-bond of triazole group toward U due to the transfer of electrons from graphene sheet to benzotriazole. DFT calculations further demonstrated that benzotriazole displayed stronger binding with U(VI) compared to carboxyl group due to higher binding energy of [Side/Surface-U-MBTA-GO] (79.745, 54.986 kcal/mol) than [MBTA-GO-COOH-U] (27.131 kcal/mol). This work will provide valuable insight into designing novel nitrogen-containing adsorbents for practical application in wastewater treatment.