•Pyrohydrolysis of SmF3 obeys the phase boundary rate law.•Sm2O3 was generated on the surface layer with parceled SmOF kernel particles.•The shrinking core model can be used to describe the mechanism of SmF3 pyrohydrolysis.•Rate-determining step of pyrohydrolysis was the surface reaction control.In order to prove the feasibility of pyrohydrolysis method of fluorides in TMSR spent fuel reprocessing, pyrohydrolysis behavior and reaction mechanism of neutron poison represented by SmF3 in moist air, have been studied by means of thermogravimetric analysis (TG). Then, reaction products in solid state were characterized by means of XRD and SEM. The results indicated that SmF3 began to hydrolyze in 773 K. Two definite breaks on TG curves were correlated to the conversions of SmF3 into SmOF and SmOF into Sm2O3, respectively. Through the simulation calculation, we found that the two stages of the reaction can both meet the second-order reaction kinetics, and their corresponding activation energies are 60.2 and 31.2 kJ/mol, respectively. From the results of dynamics simulation, the rate equation obeyed the phase boundary rate law, which was expressed by [1 − (1−x) 1/3] = kt. Further studies indicated that the rate-determining step was the surface reaction control, and the shrinking core model was applied to describe the mechanism. These results showed that pyrohydrolysis method of fluorides could be used for fuel reprocessing due to its unique reaction mechanism.There were two stages of pyrohydrolysis process of SmF3 correspond to the conversion of SmF3 into SmOF and SmOF into Sm2O3. The rate-determining step of pyrohydrolysis was the surface reaction control, and the shrinking core model was applied to describe the mechanism.

•A new extraction process using DMHMP as extractant for the recovery of uranium from irradiated thorium was proposed.•The irradiation stability of DMHMP was assessed and better than TBP.•The complexes of U(VI) and Th(IV) with DMHMP were demonstrated employing EXAFS spectroscopy.The process using DMHMP as extractant for the recovery of uranium from irradiated thorium was proposed. Firstly, the process parameters, including concentration of DMHMP, concentratation of HNO3 in feed, scrub and stripping solution, and phase ratio, were systematically optimized by batch extraction experiment. Then, a batch multistage countercurrent extraction simulation experiment was used to verify and test the process. Finally, the irradiation stability of DMHMP was assessed and compared with TBP. The results indicate that DMHMP is a potential candidate for the separation of U(VI) from bulk Th(IV). Furthermore, the complexes of U(VI) and Th(IV) with DMHMP were also demonstrated.Download high-res image (88KB)Download full-size image

•A new Th-based fuel process was evaluated using di-1-methylheptylmethylphosphonate as extractant.•The recovery of Th and U was higher than 99.8% and 99.9%, respectively.•The separation between Th and U was excellent.•The SF(Th/U) and SF(U/Th) was 5.9 × 103 and 7.1 × 103, respectively.In this paper, a reprocessing Th-based spent fuels process using di-1-methyl heptyl methyl phosphonate (DMHMP) as extractant was proposed and tested by multistage countercurrent extraction using batch simulation and centrifugal extractors. The analysis results of process samples show that the recovery of Th and U in 1A (co-extraction of Th and U), 1B (separation of Th from U) and 1C (stripping of U from organic to aqueous phase) section was more than 99.8% and 99.9%, respectively. The separation factor of Th from U and U from Th in 1B section was 5.9 × 103 and 7.1 × 103, respectively. Compared with Thorex process using TBP as extractant, the process could be operated under lower acidity and flow ratio of O:A due to the strong extraction ability of DMHMP. Thus, DMHMP would be a promising alternative extractant for Th-based spent fuels process.

•A new approach to solvent extraction employing graphene aerogel as a skeleton loading organic solution (GA-LOS) is proposed.•The GA-LOS could possess excellent extraction ability for metal ions in aqueous solution.•The GA-LOS extraction method could elimination of the aqueous-organic mixing and separation procedures in conventional solvent extraction.•The GA-LOS extraction method could reduce consumption of organic diluents and consequently less organic waste.A new approach for uranium extraction employing graphene aerogel (GA) as a skeleton loading organic solution (GA-LOS) is proposed and investigated. Firstly, the GA with super-hydrophobicity and high organic solution absorption capacity was fabricated by one-step reduction and self-assembly of graphene oxide with ethylenediamine. By adsorbing Tri-n-butyl phosphate (TBP)/n-dodecane solution to prepare GA-LOS, the extraction of U(VI) from nitric acid medium using GA-LOS was investigated and compared with conventional solvent extraction. It is found that the GA-LOS method can provide several advantages over conventional solvent extraction and adsorption due to the elimination of aqueous-organic mixing-separation procedures and easy solid-liquid separation. Furthermore, it also possesses higher extraction capacity (the saturated extraction capacity of GA loading TBP for U(VI) was 316.3 mg g−1 ) and lower consumption of organic diluents, leading to less organic waste. Moreover, the stability of GA-LOS in aqueous solution and cycling test were also studied, and it shows a remarkable regeneration capability, making it an ideal candidate for metal extraction from aqueous solution.

In this work, we have developed multiple-armed DNA tetrahedral nanostructures (TDNs) for dual-modality in vivo imaging using near-infrared (NIR) fluorescence and single-photon emission computed tomography (SPECT). We found that the presence of arm strands in TDNs remarkably enhanced their in vitro stability, allowing them to stay intact for at least 12 h in serum. By using NIR fluorescence imaging, we evaluated in mice the pharmacokinetics of TDNs, which exhibited distinctly different in vivo biodistribution patterns compared with those of double-stranded (ds)DNA. We also noticed that TDNs had twofold longer circulation time in the blood system than that of dsDNA. With the use of multiple-armed TDNs, we could precisely anchor an exact number of functional groups including tumor-targeting folic acid (FA), NIR emitter Dylight 755, and radioactive isotope 99mTc on prescribed positions of TDNs, which showed the capability of targeted imaging ability in cancer cells. Furthermore, we realized noninvasive tumor-targeting imaging in tumor-bearing mice by using both NIR and SPECT modalities.Keywords: dual-modality imaging; near-infrared fluorescence; single-photon emission computed tomography; tetrahedral DNA nanostructures; tumor targeting

DNA nanostructures have attracted great attention due to their precisely controllable geometry and great potential in various areas including bottom-up self-assembly. However, construction of higher-order DNA nanoarchitectures with individual DNA nanostructures is often hampered with the purity and quantity of these “bricks”. Here, we introduced size exclusion chromatography (SEC) to prepare highly purified tetrahedral DNA nanocages in large scale and demonstrated that precise quantification of DNA nanocages was the key to the formation of higher-order DNA nanoarchitectures. We successfully purified a series of DNA nanocages with different sizes, including seven DNA tetrahedra with different edge lengths (7, 10, 13, 17, 20, 26, 30 bp) and one trigonal bipyramid with a 20-bp edge. These highly purified and aggregation-free DNA nanocages could be self-assembled into higher-order DNA nanoarchitectures with extraordinarily high yields (98% for dimer and 95% for trimer). As a comparison, unpurified DNA nanocages resulted in low yield of 14% for dimer and 12% for trimer, respectively. AFM images cleraly presented the characteristic structure of monomer, dimer and trimer, impling the purified DNA nanocages well-formed the designed nanoarchitectures. Therefore, we have demonstrated that highly purified DNA nanocages are excellent “bricks” for DNA nanotechnology and show great potential in various applications of DNA nanomaterials.Keywords: DNA tetrahedron; highly ordered DNA nanoarchitectures; purification; quantification; size exclusion chromatography;

2-[18F]Fluoroethyl azide ([18F]FEA) and terminal alkynyl modified propioloyl RGDfK were selected in this study. [18F]FEA was prepared by nucleophilic radiofluorination of 2-azidoethyl 4-toluenesulfonate with radiochemical yield of 71 ± 4% (n = 5, decay-corrected). We assessed the various conditions of the CuAAC reaction between [18F]FEA and propioloyl RGDfK, which included peptide concentration, reaction time, temperature and catalyst dosage. The 18F-labeled-RGD peptide ([18F]F-RGDfK) could be obtained in 60 min by a two-step radiochemical synthesis route, with total radiochemical yield of 60 ± 2% (n = 3, decay-corrected) through click chemistry. [18F]F-RGDfK showed high stability in phosphate buffered saline and new-born calf serum. Micro-PET imaging at 1 h post injection of [18F]F-RGDfK showed medium concentration of radioactivity in tumors while much decreased concentration in tumors in the blocking group. These results showed that [18F]F-RGDfK obtained by click chemistry maintained the affinity and specificity of the RGDfK peptide to integrin αvβ3. This study provided useful information for peptide radiofluorination by using click chemistry.

The farnesoid-X-receptor (FXR) is a member of the nuclear hormone receptor superfamily. The FXR has critical functions in maintaining bile acid synthesis and homeostasis, liver regeneration and tumorigenesis, intestinal diseases, intestinal tumorigenesis, cholesterol gallstone disease, cholestasis, and atherosclerosis. FXR expression is strongly downregulated in liver fibrosis, hepatocellular adenoma and hepatocellular carcinoma compared to expression levels in adjacent normal tissues. Chenodeoxycholic acid (CDCA) is the most potent physiological ligand for FXR. CDCA was radiolabeled with 18 F based on the efficiency click reaction of 1,3-dipolar cycloaddition of terminal alkynes and organic azides for noninvasively evaluating the relationship between FXR and FXR-related disease. The PET tracer [18 F]8 was produced by ‘click’ labeling and showed a high non-decay corrected radiochemical yield (end of synthesis (EOS) yield = 42 ± 3% (n = 5) from aqueous [18 F]fluoride), high radiochemical purity ( > 99%), and high specific activity (> 320 GBq/μmol). [18 F]8 had a high metabolic stability in vitro and in vivo. PET imaging studies in nude mice indicated a rapid uptake of the tracer into liver tissue with uniform distribution of radioactivity in the liver. Significant accumulation of radioactivity was found in the liver, gallbladder, and intestine, while no obvious uptake was observed in other organs, such as the bladder, heart, and brain. Thus, this PET tracer represents a novel tool for early detection of abnormalities in the liver and staging of neoplasms.