Hydrogen Treatment for Superparamagnetic VO2 Nanowires with Large Room‐Temperature Magnetoresistance

One‐dimensional (1D) transition metal oxide (TMO) nanostructures are actively pursued in spintronic devices owing to their nontrivial d electron magnetism and confined electron transport pathways. However, for TMOs, the realization of 1D structures with long‐range magnetic order to achieve a sensitive magnetoelectric response near room temperature has been a longstanding challenge. Herein, we exploit a chemical hydric effect to regulate the spin structure of 1D V–V atomic chains in monoclinic VO₂ nanowires. Hydrogen treatment introduced V³⁺ (3d²) ions into the 1D zigzag V–V chains, triggering the formation of ferromagnetically coupled V³⁺–V⁴⁺ dimers to produce 1D superparamagnetic chains and achieve large room‐temperature negative magnetoresistance (?23.9 %, 300 K, 0.5 T). This approach offers new opportunities to regulate the spin structure of 1D nanostructures to control the intrinsic magnetoelectric properties of spintronic materials.     

通过不对称氢转移/动态动力学拆分合成碳环N^3-嘌呤核苷

N^3-嘌呤核苷由于可能同时被嘌呤和嘧啶代谢酶识别,因而有望作为双靶点药物应用于抗病毒治疗.报道了一种以α-(N^3-嘌呤)取代的环烷酮为原料,通过不对称氢转移反应实现动态动力学拆分,高收率高立体选择性地合成系列碳环N^3-嘌呤核苷化合物.该催化体系也适用于α-嘧啶取代的环烷酮底物,且产物通过进一步衍生,合成了2’-F-,Ac S-,N^3-修饰的碳环嘧啶核苷.     

MCM-41@Schiff base-Co(OAc)2 as an efficient catalyst for the synthesis of pyran derivatives

Research on Chemical Intermediates - Heterogeneous ordered mesoporous silica materials catalyst, MCM-41@Schiff base-Co(AcO)2, reveals high catalytic performance within the synthesis of pyran...     

酪氨酸在活性炭/水界面上的吸附

研究了不同pH值介质中酪氨酸在活性炭上的吸附行为.结果表明,pH值4.2～6.1时吸附量较大,在酪氨酸的等电点时吸附量最大;酪氨酸被吸附的主要形式是兼性离子;酪氨酸离子靠VanderWaals力吸附在活性炭/水界面上.用介质pH值对酪氨酸溶解度的影响和活性炭的表面性质解释了实验结果     

Two New Indole Alkaloids from Evodia rutaecarpa

The tyuit of Evodia rutaecarpa (Juss.) Benth is a Chinese traditional drug (Wu-Chu-Yu).The components of Wu-Chu-Yu have been studied by several groups, including indolealkaloids,quinolone alkaloids. limonoids and other kinds]. Further chemical investigationofthis drug led us to isolate two new indole alkaloids 1 and 2. This is the first time toisolate indolinone alkaloids from this plant.Wuchuyuamide I (l ), was isolated as colorless needles, m,p. 261 -262<> C (CHCI,MeOH), [Q].=# 0(c 0…     

Sol–gel based synthesis of ultrafine tetragonal BaTiO3

Ultrafine tetragonal BaTiO₃ nanocrystals have been prepared by a sol–gel based method. By adjusting the volume ratio of H₂O/DEG (diethylene glycol) in the solutions, hydrolysis rate of tetra-n-butyl titanate was strongly inhibited and the particle size could be controlled as small as 4–8 nm. The powder X-ray diffraction and transmission electron microscopy characterizations exhibit that the nanocrystals are spherical and well crystallized. The Raman spectrum shows the products are composed of the orthorhombic phase and tetragonal phase. The Fourier transform infrared spectrum revealed that a surface modification layer was formed around the BaTiO₃ nanocrystals, which can prevent them from aggregation and help to form a stable, high solid content sol.     

Photofunctional Eu3+/Tb3+ hybrids through sulfoxide linkages: coordination bonds construction, characterization and luminescence

New kinds of organic-inorganic hybrid materials consisting of rare earth (Eu(3+), Tb(3+)) complexes covalently bonded to a silica-based network have been obtained by a sol-gel approach. Three novel versatile molecular building blocks containing sulfoxide organic units have been synthesized by methylene modification reaction, which are used as the ligands of rare earth ions and also as siloxane network precursors. The obtained hybrids are characterized by chemical analysis and spectroscopic methods such as FTIR and UV; XRD and SEM. Photoluminescence measurements on the prepared hybrids were performed showing the intra-4f(n) emission in the visible (Eu(3+), Tb(3+)) region and in all the cases being sensitized by the sulfoxide ligands. The emission quantum efficiency and the Judd-Ofelt intensity parameters of Eu(3+) hybrid materials were also investigated in detail.     

Fragmentation studies of pentacoordinated bisaminoacylspirophosphoranes by negative electrospray ionization mass spectrometry

Fragmentation pathways of a series of pentacoordinated bisaminoacylspirophosphoranes were elucidated by electrospray ionization multistage mass spectrometry (ESI-MS(n)) in negative mode. The deprotonated ions of pentacoordinated bisaminoacylspirophosphoranes tend to eliminate a corresponding amino acid to form base peak. The hydrogen/deuterium exchange experiment, the high-resolution mass spectrometry, (13)C stable isotope labeling experiment and theoretical calculations were used to rationalize the proposed fragmentation pathways and to verify the differences between the fragmentation pathways. The results indicate that the negative molecular ions of pentacoordinated bisaminoacylspirophosphoranes dissociate through its open-chain tricoordinated tautomers. The relative Gibbs free energies (ΔG) of the product ions and proposed fragmentation pathways were estimated using the B3LYP/6-31 + + G(d, p) model. The results have some potential applications in the identification structures of similar spirophosphorane compounds by ESI-MS(n).     

A facile one-pot method to high-quality Ag-graphene composite nanosheets for efficient surface-enhanced Raman scattering

Ag-graphene composite nanosheets (AGCN) with adjustable size and well-controlled densities of Ag nanoparticles (Ag NPs) using Poly(N-vinyl-2-pyrrolidone) (PVP) as a reductant and stabilizer are reported. The obtained AGCN substrate is extremely suitable for surface-enhanced Raman spectroscopy (SERS).     

Accessing the long-lived emissive 3IL triplet excited states of coumarin fluorophores by direct cyclometallation and its application for oxygen sensing and upconversion

We studied four cyclometallated Pt(II) complexes, in which the thiazo-coumarin ligands (Pt-2, Pt-3 and Pt-4) or the phenylthiazo ligand (Pt-1) were directly cycloplatinated. Pt-2 shows intense absorption in visible region but other complexes show blue-shifted absorption. Room temperature phosphorescence was observed for all the complexes, and the emission wavelength is dependent on the size of the π-conjugation, not the intramolecular charge transfer (ICT) feature of the C^N ligands. Pt-2 shows longer phosphorescence lifetime (τ = 20.3 μs) than other complexes (below 2.0 μs). Furthermore, Pt-2 shows phosphorescence quantum yield Φ = 0.37, whereas Pt-3 and Pt-4 show much smaller Φ values (0.03 and 0.01, respectively). DFT/TDDFT calculations indicate (3)IL triplet excited states for the complexes. The complexes were used as for luminescence O(2) sensing and triplet-triplet-annihilation (TTA) based upconversion. Stern-Volmer quenching constant K(SV) = 0.026 Torr(-1) was observed for Pt-2, ca. 89-fold of that of Pt-3. TTA upconversion is achieved with Pt-2 (λ(em) = 400 nm with λ(ex) = 473 nm, anti-Stokes shift is 0.47 eV, excitation power density is at 70 mW cm(-2)). The upconversion quantum yield with Pt-2 as triplet sensitizer is up to 15.4%. The TTET efficiency (K(SV) = 1.33 × 10(5) M(-1), k(q) = 6.57 × 10(9) M(-1) s(-1). DPA as quencher) of Pt-2 is 34-fold of the model complex [Ru(dmb)(3)][PF(6)](2). Our results show that the (3)IL state can be readily accessed by direct cyclometallation of organic fluorophores and this approach will be useful for preparation and applications of transition metal complexes that show intense absorption in visible region and the long-lived emissive (3)IL excited states.