Theoretical design of polyazole based ligands for the separation of Am(Ⅲ)/Eu(Ⅲ)

The extraction of radioactive minor actinides(An(Ⅲ))from lanthanides(Ln(Ⅲ))is an extremely impor-tant step in nuclear waste reprocessing.Designing ligands with high-performance actinide-selectivity re-mains an essential task.Recent works have reported that some polyazole based ligands exhibit good An(Ⅲ)/Ln(Ⅲ)separation performance.Herein,we first evaluated the effects of different polyazole side chains on the Am(Ⅲ)/Eu(Ⅲ)selectivity by exploring three pyridine-derived polyazole ligands L^(1),L^(2)and L^(3)with 1,2,4-triazole,1,2,3-triazole,and pyrazole side chains,respectively,using scalar relativistic theoretical methods.The coordination structures,bonding properties and thermodynamic behaviors of AmL(NO_(3))_(3)and EuL(NO_(3))_(3)complexes were investigated,which clarifies that the side chains do affect the electronic structure of ligand and its selectivity for Am(Ⅲ)/Eu(Ⅲ)ions.Moreover,L^(1)with 1,2,4-triazole side chains exhibited the highest selectivity for Am(Ⅲ)over Eu(Ⅲ)while the lowest complexation ability for metal ions among the three pyridine-derived polyazole ligands.Subsequently,we designed a new ligand L^(4)con-taining 1,2,4-triazole side chains and a preorganized phenanthroline backbone.Theoretically,such a new ligand was verified to show stronger complexation ability and higher selectivity for Am(Ⅲ)/Eu(Ⅲ)ions than L^(1).This work clarifies the complexation nature of polyazole based ligands with Am(Ⅲ)/Eu(Ⅲ)ions and provides design strategies for highly efficient polyazole based ligands for An(Ⅲ)/Ln(Ⅲ)separation.

Theoretical perspectives on the reduction of Pu(Ⅳ)and Np(Ⅵ)by methylhydrazine in HNO_(3)solution:Implications for Np/Pu separation

Effective adjustment and control of the oxidation state of plutonium(Pu)and neptunium(Np)is an indispensable component of Np/Pu separation in spent nuclear fuel reprocessing.Some hydrazine derivatives including methylhydrazine(CH_(3)N_(2)H_(3))effectively achieves the reduction of Np(Ⅵ)to Np(V)without reducing Pu(Ⅳ).Herein,we explored the reduction mechanisms of Pu(Ⅳ)and Np(Ⅵ)by CH_(3)N_(2)H_(3)in HNO_(3)solution using scalar-relativistic density functional theory.We elucidated the difference in the reduction mechanism between Np(Ⅵ)and Pu(Ⅳ)ions by CH_(3)N_(2)H_(3).The energy barrier for the reduction of[NpⅥO_(2)(H_(2)O)_(5)]^(2+)and[NpⅥO_(2)(NO_(3))(H_(2)O)_(3)]^(+)by CH_(3)N_(2)H_(3)is largely different due to the coordination of nitrate ion.Moreover,the energy barrier of the reduction of[NpⅥO_(2)(H_(2)O)_(5)]^(2+)is apparently lower than that of[PuⅣ(NO_(3))_(2)(H_(2)O)_(7)]^(2+),which is in line with the experimental observations.The results of Mayer bond order and localized molecular orbitals clarify the structural evolution of the reaction pathways.Analysis of the spin density demonstrates that the first Np(Ⅵ)and Pu(Ⅳ)reduction belongs to the outer-sphere electron transfer and the second Np(Ⅵ)and Pu(Ⅳ)reduction is the hydrogen transfer.This study explains theoretically why CH_(3)N_(2)H_(3)reduces Np(Ⅵ)but not Pu(Ⅳ),and helps to design promising reductants for the Np/Pu separation in spent nuclear fuel reprocessing.

Self-Navigated 3D Acoustic Tweezers in Complex Media Based on Time Reversal

Acoustic tweezers have great application prospects because they allow noncontact and noninvasive manipulation of microparticles in a wide range of media.However,the nontransparency and heterogeneity of media in practical applications complicate particle trapping and manipulation.In this study,we designed a 1.04 MHz 256-element 2D matrix array for 3D acoustic tweezers to guide and monitor the entire process using real-time 3D ultrasonic images,thereby enabling acoustic manipulation in nontransparent media.Furthermore,we successfully performed dynamic 3D manipulations on multiple microparticles using multifoci and vortex traps.We achieved 3D particle manipulation in heterogeneous media(through resin baffle and ex vivo macaque and human skulls)by introducing a method based on the time reversal principle to correct the phase and amplitude distortions of the acoustic waves.Our results suggest cutting-edge applications of acoustic tweezers such as acoustical drug delivery,controlled micromachine transfer,and precise treatment.

Theoretical studies on the complexation of Eu(Ⅲ) and Am(Ⅲ) with HDEHP： structure, bonding nature and stability

Separation of trivalent lanthanides （Ln（Ⅲ）） and actinides （An（Ⅲ）） is a key issue in the advanced spent nuclear fuel repro- cessing. In the well-known trivalent actinide lanthanide separation by phosphorus reagent extraction from aqueous komplexes （TALSPEAK） process, the organophosphorus ligand HDEHP （di-（2-ethylhexyl） phosphoric acid） has been used as an efficient reagent for the partitioning of Ln（Ⅲ） from An（Ⅲ） with the combination of a holdback reagent in aqueous lactate buffer solu- tion. In this work, the structural and electronic properties of Eu3＋ and Am3＋ complexes with HDEHP in nitric acid solution have been systematically explored by using scalar-relativistic density functional theory （DFT）. It was found that HDEHP can coordinate with M（Ⅲ） （M=Eu, Am） cations in the form of hydrogen-bonded dimers HL2 （L=DEHP）, and the metal ions pre- fer to coordinate with the phosphoryl oxygen atom of the ligand. For all the extraction complexes, the metal-ligand bonds are mainly ionic in nature. Although Eu（Ⅲ） complexes have higher interaction energies, the HL2- dimer shows comparable affini- ty for Eu（Ⅲ） and Am（Ⅲ） according to thermodynamic analysis, nonahydrate. It is expected that this work could provide insightful HDEHP at the molecular level. which may be attributed to the higher stabilities of Eu（Ⅲ） information on the complexation of An（Ⅲ） and Ln（Ⅲ） with