应力对退火态Sm-Fe-BGMF磁学性能的影响

利用离子束溅射(IBSD)法,在盖玻片衬底上制备Sm-Fe-B超磁致伸缩薄膜(GMF)样品;并在退火过程中对其施加预应力,研究应力对退火态Sm-Fe-B薄膜磁畴结构、软磁性能及磁致伸缩性能的影响并分析其差异产生的原因。结果表明:退火过程中施加预应力能使薄膜磁畴结构发生显著变化,通过改善退火态薄膜的微结构与应力状态,能有效提高薄膜的软磁性能与磁致伸缩性能;与自由退火态样品比较,应力退火态样品具有较明显的垂直各向异性,虽然在低场磁敏性方面略有降低,但是在饱和磁致伸缩性能方面有较大提高。     

稀土掺杂NaLuF4超薄纳米片的上转换发光特性研究

基体材料的特性和敏化离子对于稀土发光离子的发光特性有显著影响。通过在高效上转换基体材料NaLuF4掺杂Nd3+和Yb3+两种离子共同敏化发光离子Er3+,采用水热法合成了Nd3+,Yb3+,Er3+三种稀土离子掺杂的NaLuF4超薄六角纳米片,利用透射电镜、X射线衍射确定了其形貌和晶体结构。在980 nm红外光激发下测试了其上转换发光特征、荧光衰减、总体发光强度。荧光光谱表明未掺杂Nd3+离子的样品,随着Yb3+敏化离子浓度的增加(2%~12%(摩尔分数)),中心波长为539 nm的绿光强度相对于中心波长为654 nm的红光单调减弱;掺杂3%Nd3+的绿光发射强度随Yb3+离子增加先增强,后减弱。结合简化能级图分析了上转换发光过程与机制。     

化学标准物质期间核查方法

从认可实验室管理的角度,阐述了化学标准物质期间核查的目的和意义。化学标准物质常见期间核查方法有实验室比对或能力验证、标准物质间比对、控制图法、允差法及标定法。结合实例介绍了化学标准物质期间核查的具体过程,为开展化学标准物质期间核查工作提供参考。     

Salt‐Induced Fabrication of Superhydrophilic and Underwater Superoleophobic PAA‐g‐PVDF Membranes for Effective Separation of Oil‐in‐Water Emulsions

Conventional polymer membranes suffer from low flux and serious fouling when used for treating emulsified oil/water mixtures. Reported herein is the fabrication of a novel superhydrophilic and underwater superoleophobic poly(acrylic acid)‐grafted PVDF filtration membrane using a salt‐induced phase‐inversion approach. A hierarchical micro/nanoscale structure is constructed on the membrane surface and endows it with a superhydrophilic/underwater superoleophobic property. The membrane separates both surfactant‐free and surfactant‐stabilized oil‐in‐water emulsions under either a small applied pressure (<0.3 bar) or gravity, with high separation efficiency and high flux, which is one to two orders of magnitude higher than those of commercial filtration membranes having a similar permeation property. The membrane exhibits an excellent antifouling property and is easily recycled for long‐term use. The outstanding performance of the membrane and the efficient, energy and cost‐effective preparation process highlight its potential for practical applications.     

3D metal-organic frameworks based on elongated tetracarboxylate building blocks for hydrogen storage

Two 3D metal-organic frameworks (MOFs) with a new biphenol-derived tetracarboxylate linker and Cu(II) and Zn(II) metal-connecting points were synthesized and characterized by single-crystal X-ray crystallographic studies. The two isostructural MOFs exhibit distorted PtS network topology and show markedly different framework stability. The porosity and hydrogen uptake of the frameworks were determined by gas adsorption experiments.     

Amorphous Mo-doped NiS0.5Se0.5 Nanosheets@Crystalline NiS0.5Se0.5 Nanorods for High Current-density Electrocatalytic Water Splitting in Neutral Media

It is vitally important to develop highly active, robust and low-cost transition metal-based electrocatalysts for overall water splitting in neutral solution especially at large current density. In this work, amorphous Mo-doped NiS_0.5Se_0.5 nanosheets@crystalline NiS_0.5Se_0.5 nanorods (Am−Mo−NiS_0.5Se_0.5) was synthesized using a facil one-step strategy. In phosphate buffer saline solution, the Am−Mo−NiS_0.5Se_0.5 shows tiny overpotentials of 48 and 209 mV for hydrogen evolution reaction (HER), 238 and 514 mV for oxygen evolution reaction (OER) at 10 and 1000 mA cm⁻², respectively. Moreover, Am−Mo−NiS_0.5Se_0.5 delivers excellent stability for at least 300 h without obvious degradation. Theoretical calculations revealed that the Ni sites in the defect-rich amorphous structure of Am−Mo−NiS_0.5Se_0.5 owns higher electron state density and strengthened the binding energy of H₂O, which will optimize H adsorption/desorption energy barriers and reduce the adsorption energy of OER determining step.     

Enhanced Energy Transfer in A π-Conjugated Covalent Organic Framework Facilitates Excited-State Nickel Catalysis

Covalent organic frameworks (COFs) have received broad interest owing to their permanent porosity, high stability, and tunable functionalities. COFs with long-range π-conjugation and photosensitizing building blocks have been explored for sustainable photocatalysis. Herein, we report the first example of COF-based energy transfer Ni catalysis. A pyrene-based COF with sp² carbon-conjugation was synthesized and used to coordinate Ni^II centers through bipyridine moieties. Under light irradiation, enhanced energy transfer in the COF facilitated the excitation of Ni centers to catalyze borylation and trifluoromethylation reactions of aryl halides. The COF showed two orders of magnitude higher efficiency in these reactions than its homogeneous control and could be recovered and reused without significant loss of catalytic activity.     

Isolated Electron-Rich Ruthenium Atoms in Intermetallic Compounds for Boosting Electrochemical Nitric Oxide Reduction to Ammonia

The direct electrochemical nitric oxide reduction reaction (NORR) is an attractive technique for converting NO into NH₃ with low power consumption under ambient conditions. Optimizing the electronic structure of the active sites can greatly improve the performance of electrocatalysts. Herein, we prepare body-centered cubic RuGa intermetallic compounds (i.e., bcc RuGa IMCs) via a substrate-anchored thermal annealing method. The electrocatalyst exhibits a remarkable NH₄⁺ yield rate of 320.6 μmol h⁻¹ mg⁻¹_Ru with the corresponding Faradaic efficiency of 72.3 % at very low potential of −0.2 V vs. reversible hydrogen electrode (RHE) in neutral media. Theoretical calculations reveal that the electron-rich Ru atoms in bcc RuGa IMCs facilitate the adsorption and activation of *HNO intermediate. Hence, the energy barrier of the potential-determining step in NORR could be greatly reduced.     

Stereospecific Aminative Cyclizations Triggered by Intermolecular Aza-Prilezhaev Alkene Aziridination

Under acidic reaction conditions (TFA), deprotection of BocNR(OSO₂R) reagents triggers intermolecular aminative cyclizations of alkenes equipped with pendant nucleophiles. The processes are predicated on a sequence of stereospecific intermolecular aza-Prilezhaev aziridination followed by stereospecific S_N2-like opening by the pendant nucleophile. The method offers broad scope with respect to the nucleophile (N-, O- or C-based), alkene and cyclization mode, allowing the installation of two contiguous stereocenters under operationally simple conditions.     

高效液相色谱测定牛奶中邻苯二甲酸酯的方法研究

建立了针对欧盟指令2007/19/EC中禁止与食品接触的6种邻苯二甲酸酯(BBP、DBP、DEHP、DNOP、DINP和DIDP)的RP-HPLC测定方法.样品用甲醇、正己烷.甲基叔丁基醚(ⅥV=1:1)提取,经冷冻去脂、液液萃取和硅胶固相萃取净化后,用ODS柱(250×4.6mm,5μm)分离,UV 224 nm检测.结果表明,BBP和DBP在0.05～80μg/mL、DEHP和DNOP在0.1～80μg/mL、DINP和DIDP在0.5～80μg/mL的质量浓度范围内,峰面积与质量浓度呈线性关系,相关系数(r2)均大于0.998.方法检测限分别为:BBP 0.15μg/g、DBP 0.1μg/g、DEHP和DNOP 0.2μg/g、DINP和DIDP 0.6μg/g;6种PAEs的添加量在最大残留限量值的0.2、1和2倍时,其平均回收率为80.7%～102.3%,相对标准偏差为1.7%～9.0%.所建立的方法经济、准确、可靠,满足欧盟指令中6种邻苯二甲酸酯限量的检测要求.