Co/Ni多层膜垂直磁各向异性的研究

采用直流磁控溅射法在玻璃基片上制备了Pt底层的Co/Ni多层膜样品, 对影响样品垂直磁各向异性的各因素进行了调制, 通过样品的反常霍尔效应系统的研究了Co/Ni多层膜的垂直磁各向异性. 结果表明, 多层膜中各层的厚度及周期数对样品的反常霍尔效应和磁性有重要的影响. 通过对多层膜各个参数的调制优化, 最终获得了具有良好的垂直磁各向异性的Co/Ni多层膜最佳样品Pt(2.0)/Co(0.2)/Ni(0.4)/Co(0.2)/Pt(2.0), 经计算, 该样品的各向异性常数K_eff 达到了3.6×10⁵ J/m³, 说明样品具备良好的垂直磁各向异性. 最佳样品磁性层厚度仅为0.8 nm, 样品总厚度在5 nm以内, 可更为深入的研究其与元件的集成性.     

Dependence of current-voltage characteristics of pseudomorphic AlAs/In0.53a0.47s/InAs resonant tunneling diodes on quantum well widths

This paper studies the dependence of I-V characteristics on quantum well widths in AlAs/In_0.53Ga_0.47As and AlAs/In_0.53Ga_0.47As/InAs resonant tunneling structures grown on InP substrates. It shows that the peak and the valley current density in the negative differential resistance region are closely related with quantum well width. The measured peak current density, valley current densities and peak-to-valley current ratio of resonant tunneling diodes are continually decreasing with increasing well width.     

Native amine-directed site-selective C(sp3)-H arylation of primary aliphatic amines with aryl iodides

Direct C(sp³)-H functionalization of N-unprotected aliphatic amines represents one of the most efficient and straightforward strategies for amine synthesis. Despite some recent progress in this field, the NH₂-directed γ-C(sp³)-H arylation of primary aliphatic amines except α-amino esters remained an unmet challenge. In this report, we established a simple and efficient method for site-selective C(sp³)-H arylation of primary aliphatic amines by aryl iodides. In the presence of only 5 mol% Pd(OAc)₂, a wide range of aliphatic amines including O-benzyl and O-silyl amino alcohols were arylated at γ- or δ-positions by aryl iodides containing a broad scope of functional groups. The synthetic application of this method had also been demonstrated by large-scale synthesis, the synthesis of a fingolimod analogue, and the conjugation with natural d-menthol and fluorescent 1,8-naphthalimide.     

两种基于B5On(n=11, 12)簇构筑的具有深紫外吸收的硼酸盐

以碱金属和碱土金属为模板, 在溶剂热条件下合成了两种具有深紫外吸收特性的硼酸盐Na₂Ba· [B₅O₈(OH)]₂·2H₂O(1)和KSr[B₅O₈(OH)₂](2), 并利用单晶X射线衍射(SCXRD)、 粉末X射线衍射(PXRD)、 傅里叶变换红外(FTIR)光谱、 紫外-可见吸收光谱(UV-Vis)和热重分析(TG)等手段对化合物的结构和性能进行了研究. 结果表明, 化合物1可归属于单斜晶系P2/c空间群, 结构中四连接的B₅O₁₀(OH)簇单元通过共氧连接形成含有两种9-元环窗口的二维层; 化合物2结晶于单斜晶系C2/c空间群, 结构中四连接的B₅O₁₀(OH)₂簇单元则通过共氧交替连接构筑了罕见的含有8-/12-元环孔道的二维褶皱层. 两种基于B₅O_n(n=11, 12)簇单元构筑的化合物均具有低于200 nm的深紫外吸收边, 在紫外/深紫外区具有潜在的应用价值.     

Two New Borates Built by Different Types of {B9} Cluster Units

Two new belt-like borates Na₄[B₉O₁₄(OH)₃]·0.5H₂O(1) and Na₅[B₉O₁₄(OH)₄](2) have been synthesized under solvothermal conditions. Both compounds contain unprecedented B₉O₁₆(OH)_n^(n+5)-[n=3(1), 4(2)] clusters, which are constructed from four B₃O₃ rings via three BO₄ tetrahedra. Compound 1 exhibits a rare 1D belt with two types of 8-membered ring(MR) windows based on B₉O₁₆(OH)₃^8- clusters. Compound 2 features two different 1D belts built by different B₉O₁₆(OH)₄^9- units, which is first discovered in borate family. UV-Vis diffuse reflectance spectra reveal that compounds 1 and 2 have the cut-off edges below 190 nm, indicating that they may have potential application in deep UV(DUV) region.     

Long-Lived Multiple Charge Separation by Proton-Coupled Electron Transfer

Multiple charge separation has been successfully realized by a proton-coupled electron transfer reaction in an organic cocrystal. Benefiting from the adjustable electronic energy level of the electron donor and acceptor through thermal-induced proton migration, distinct optical absorption behaviors combined with color changes to blue or green are observed in these charge-separated states. It is of interest to note that such charge-separated states exhibit a longer lifetime of over a month as a result of the excellent coplanarity and π-π interaction of the electron acceptors. Moreover, the enhanced absorption toward longer wavelengths endows the charge-separated state with near-infrared (808 nm) photothermal conversion for imaging and bacterial inhibition, whereby the conversion performance can be controlled by the degree of proton migration.     

In Situ Photoisomerization of an Azobenzene-Based Triple Helicate with a Prolonged Thermal Relaxation Time

The phosphate-coordination triple helicates A₂L₃ (A=anion) with azobenzene-spaced bis-bis(urea) ligands (L) have proven to undergo a rare in situ photoisomerization (without disassembly of the structure) rather than the typically known, stepwise “disassembly-isomerization-reassembly” process. This is enabled by the structural self-adaptability of the “aniono” assembly arising from multiple relatively weak and flexible hydrogen bonds between the phosphate anion and bis(urea) units. Notably, the Z→E thermal relaxation rate of the isomerized azobenzene unit is significantly decreased (up to 20-fold) for the triple helicates compared to the free ligands. Moreover, the binding of chiral guest cations inside the cavity of the Z-isomerized triple helicate can induce optically pure diastereomers, thus demonstrating a new strategy for making light-activated chiroptical materials.     

A surface enhanced Raman study of the adsorption of tris(2,2-bipyridine)ruthenium(II) and substituted analogues on chemically-deposited silver films

The surface enhanced resonance Raman spectroscopy (SERRS) of a series of tris(2,2′-bipyridine)ruthenium(II) complexes on chemically produced silver films is reported. The SERR spectra of [Ru(bipy)₃]²⁺, several tris complexes of Ru(II) containing substituted 2,2′-bipyridine (4,4′-dimethyl-,4,4′diphenyl-, 4,4′-diamino- and 4,4′-diethylcarboxylate-2,2′-bipyridine) ligands and the neutral cis-bis complexes [Ru(bipy)₂(NCS)₂] and [Ru(bipy)₂Cl₂] show very high band intensities. The large enhancement arises from the combination of the inherent resonance Raman effect and the surface plasmon resonance (due to the rough nature of the silver film). The molecules are not chemisorbed on the silver surface and hence the enhancement occurs solely via the electromagnetic mechanism. Ale SERR spectra are virtually free of the fluorescence which dominates the corresponding RR spectra thus illustrating the use of SERRS in the vibrational spectroscopy of strongly luminescing species. The SERRS spectra of the substituted 2,2′-bipyridine complexes are discussed.