Growth and spectral properties of Yb:Ca0.28Ba0.72Nb2O6 disordered crystal

The growth, XRD patterns, spectral properties, and fluorescence decays of Yb:Ca_0.28Ba_0.72Nb₂O₆ (Yb:CBN) with doping concentration of 1 at.% and 5 at.% were studied. The peak absorption cross-section and the emission cross-section were calculated. Larger Stark splitting of Yb:CBN offers the prospect of the quasi-four level laser operation.     

系列Sm3+配合物的合成、结构及光物理性能

采用水热方法合成了4种Sm³⁺配合物, 即{[SmZn(2,5-pdc)₂(tp)_0.5(H₂O)]·2H₂O}_n(1), [Sm₂Zn₂(C₆H₅COO)₁₀(Imh)₂(H₂O)₂](2), {[Sm₂(NO₂C₆H₄COO)₆(H₂O)₄]·H₂O}_n(3)和{[SmN(CH₂COO)₃(H₂O)₂]·H₂O}_n(4)[2,5-pdc=2,5-吡啶二羧酸根, tp=对苯二甲酸根, C₆H₅COO=苯甲酸根, Imh=咪唑, NO₂C₆H₄COO=对硝基苯甲酸根, N(CH₂COO)₃=氨三乙酸根]. 通过单晶X射线衍射确定了其晶体结构. 在室温下测定了其红外光谱、 紫外-可见-近红外光谱以及在近红外区和可见区的发射光谱. 结果表明, 4种配合物在近红外区或可见区均出现Sm³⁺离子的特征发射. 这是形成配合物后, Zn-配体部分和配体对Sm³⁺离子发光的敏化作用所致. 此外, 讨论了不同有机配体或d过渡金属离子对Sm³⁺离子发光的影响, 并分析了配合物中Sm³⁺离子的近红外发射带位移、 劈裂和加宽的原因.     

Anisotropic Cu@Cu-BTC core-shell nanostructure for memory device

The activity and stability of Cu nanostructures strongly depend on their sizes, morphology and structures.Here we report the preparation of two-dimensional(2 D) Cu@Cu-BTC core-shell nanosheets(NSs). The thickness of the Cu NSs could be tuned to sub-10 nm through a mild etching process, in which the Cu-BTC in situ grow along with the oxidation on the surface of the Cu NSs. This unique strategy can also be extended to synthesize one-dimensional(1 D) Cu@Cu-BTC nanowires(NWs). Furthermore, the obtained Cu@Cu-BTC NSs could be applied as an effective material to the memory device with the write-onceread-many times(WORM) behavior and the high I_(ON)/I (OFF) ratio(2.7 × 10~3).     

Two‐Dimensional CuSe Nanosheets with Microscale Lateral Size: Synthesis and Template‐Assisted Phase Transformation

Semiconducting nanosheets with microscale lateral size are attractive building blocks for the fabrication of electronic and optoelectronic devices. The phase‐controlled chemical synthesis of semiconducting nanosheets is of particular interest, because their intriguing properties are not only related to their size and shape, but also phase‐dependent. Herein, a facile method for the synthesis of phase‐pure, microsized, two‐dimensional (2D) CuSe nanosheets with an average thickness of approximately 5 nm is demonstrated. These hexagonal‐phased CuSe nanosheets were transformed into cubic‐phased Cu_2?xSe nanosheets with the same morphology simply by treatment with heat in the presence of Cu^I cations. The phase transformation, proposed to be a template‐assisted process, can be extended to other systems, such as CuS and Cu_1.97S nanoplates. Our study offers a new method for the phase‐controlled preparation of 2D nanomaterials, which are not readily accessible by conventional wet‐chemical methods.     

Crystal growth and optical properties of LuYAG:Ce single crystal

Crystals of Ce³⁺-doped (Lu_xY_1?x)₃Al₅O₁₂ (LuYAG) have been grown and studied by X-ray powder diffraction, emission spectroscopy, excitation spectroscopy and X-ray excited fluorescence spectroscopy. The X-ray powder diffraction pattern revealed that the as-grown LuYAG:Ce crystal possessed the garnet structure. Compared with Ce³⁺-doped Y₃Al₅O₁₂ (YAG), the absorption bands associated with the 4f–5d transition shifted to shorter wavelengths, the emission band that originated from a transition from the lowest 5d level to the ²F ground state of the Ce³⁺ ions shifted to the blue, which was probably due to a larger Stokes shift of the emission, and the reduction of relative intensity of antisite defect emission in the X-ray excited fluorescence spectra revealed that introducing Lu ions into YAG could reduce the antisite defect.     

Establishment of CRISPR/Cas9-Mediated Knock-in System for Porcine Cells with High Efficiency

Applied Biochemistry and Biotechnology - Since the birth of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9, the new genome engineering technology has become a hot topic in...     

Exploring and comparing two means of preparing and fractionating oligomeric proanthocyanidins from mangosteen pericarp: gel filtration chromatography and progressive solvent precipitation

The preparation and fractionation of oligomeric proanthocyanidins (OPCs) are particularly important for the application of tannins in the biomedical field. By use of two different methods—gel filtration chromatography (GFC) with Sephadex LH-20 and progressive solvent precipitation—the OPCs were prepared and fractionated from mangosteen pericarp. The fractions were compared by reversed-phase and normal-phase high-performance liquid chromatography–electrospray ionization mass spectrometry and gel permeation chromatography. GFC directly purified oligomers (monomer to pentamer) with polydispersity values close to 1 and generated fractions with a higher level of total phenols (800.59 mg gallic acid equivalents per gram) but a lower yield (7.72%). Progressive solvent precipitation rapidly prepared and fractionated OPCs with a lower level of total phenols (609.57 mg gallic acid equivalents per gram) but a higher yield (24.74%) and higher polydispersity. Additionally, we found pronounced structural and quantitative differences among different tannin-rich fractions, and fractions obtained by GFC better reflected the structural diversity and complexity of OPCs from mangosteen pericarp. This study presents different ways of preparing and fractionating OPCs in the biomedical field.