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991.
Song-Tao Dong Bin-Bin Zhang Lunyong Zhang Y.B. Chen Jian Zhou Shan-Tao Zhang Zheng-Bin Gu S.H. Yao Yan-Feng Chen 《Physics letters. A》2014
A series of Gd-doped Sr2IrO4 single crystals were grown using a flux method. Analysis of the temperature-dependent resistance of these crystals reveals that these samples show two-dimensional weak localization at 150 to 300 K, while three-dimensional variable range hopping (VRH) behavior is observed at temperatures lower than 150 K. Two localization lengths are observed in the VRH behavior, with a transition temperature of around 88 K. Correspondingly, temperature-dependent magnetization observations along the ab-plane reveal magnetic anomalies at both 150 and 85 K. This work demonstrates the correlation between the electrical and magnetic properties of 5d transition-metal compounds. 相似文献
992.
Fast and accurate detection of complex samples in either medical diagnosis or food safety analysis are of great significance for the safeguarding of human health. Magnetic relaxation switches (MRS) technique based on superparamagnetic nanoparticles (SMP) is the combination of nano-biotechnology, nuclear magnetic resonance, chemistry and immunoassay. MRS assay has the characteristics of high sensitivity and specificity, as well as nondestructive and time-saving, and can be used in turbid complex samples. In this paper, with a brief discussion about the detection theory of superparamagnetic nanosensor, the target type, structural characteristics, limit of detection, state of magnetic nanoparticles and the change of T2 value of MRS were reviewed. The research progresses of magnetic relaxation switch sensor in medical diagnosis of different biomarkers and the analysis of food hazard factor were also summarized. Accordingly, future research targets from three aspects, e.g., preparation and modification of magnetic nanoparticles, the improvement of detection sensitivity and construction of high flux magnetic relaxation switch sensor, were put forward. 相似文献
993.
《Electroanalysis》2018,30(5):901-909
We report in this work the development of a novel capacitance electrochemical sensors based on silicon nitride substrate (Si3N4) chemically modified with a structure of Cobalt phthalocyanine, C,C,C,C‐tetracarboxylic acid‐Polyacrylamide (Co(II)Pc‐PAA). This sensitive layer was tested with and without magnetic nanoparticles (MNP) for perchlorate ( ) detection. The developed chemical sensor with Si3N4/APTES‐MNP/Co(II)Pc‐PAA structure has shown a better performance when compared to the other structure based on Si3N4/Co(II)Pc‐PAA. Contact angle measurements (CAM) and atomic force microscopy (AFM) characterizations have been performed to characterize the functionalization of the chemical sensors surface. Under the optimized structure of the chemical sensor, electrochemical measurements were carried out using Mott‐Schottky analysis for detection within the large range of 10−10 to 10−4 M with a very low detection limit of 2×10−10 M. The chemical sensor has demonstrated a high selectivity toward when compared to other interfering anions such as Cl−, SO42−, and CO32−. The present capacitive chemical sensor is very promising for sensitive and rapid detection of for environmental applications. 相似文献
994.
《无机化学与普通化学杂志》2018,644(12-13):560-563
One new two‐dimensional (2D) CuII polymer [Cu(CHDA)(H2O)]n ( 1 ) was synthesized solvothermally based on 1,1‐cyclohexanediacetic acid (H2CHDA) ligand. Single‐crystal X‐ray diffraction analysis reveals that 1 has a 2D framework structure consisting of paddle‐wheel dinuclear [Cu2] cluster unit and CHDA2– connector, which bears a 4‐connected sql network with Schläfli symbol of (44.62). Magnetic studies indicate the presence of strong antiferromagnetic coupling (J = –302 cm–1) between the two CuII ions in the paddle‐wheel dicopper(II) entity. 相似文献
995.
《无机化学与普通化学杂志》2018,644(11):504-511
The coordination polymers (CPs), [Ni(L)(H2O)4]n ( 1 ), [Co(HL)2(H2O)2]n ( 2 ), {[Cu(L)(H2O)3] · H2O}n ( 3 ), [Mn(L)(H2O)2]n ( 4 ), [Cd(L)(H2O)2]n ( 5 ), and {[Zn2(L)2] · H2O}n ( 6 ), were solvothermally synthesized by employing the imidazol‐carboxyl bifunctional ligand 4‐(1H‐imidazol‐1‐yl) phthalic acid (H2L). Single‐crystal X‐ray diffraction indicated that the L2–/HL– ligands display various coordination modes with different metal ions in 1 – 6 . Complexes 1 and 2 show one‐dimensional (1D) chain structures, whereas complexes 3 – 6 show 2D layered structures. The magnetic properties of these complexes were investigated. Complexes 1 and 3 indicate weak ferromagnetic interactions, whereas complexes 2 and 4 demonstrate antiferromagnetic interactions. In addition, luminescence properties of 5 and 6 were measured and studied in detail. 相似文献
996.
《中国化学会会志》2018,65(6):696-705
Magnetic porous polymeric microspheres containing epoxy groups were prepared by suspension polymerization (denoted as magnetic Fe3O4@GEM microspheres). Fe3O4@GEM with a specific surface area of 30.41 m2/g, average pore diameter of 17.13 nm, and pore volume of 0.13 cm3/g exhibited superparamagnetic behavior with the saturation magnetization of 7.1 emu/g. The content of epoxy groups on Fe3O4@GEM was 0.22 mmol/g. Pseudomonas sp. lipase (PSL) was covalently immobilized onto the Fe3O4@GEM microspheres through the reaction between the amino groups of the enzyme and the epoxy groups on the microspheres. PSL/Fe3O4@GEM exhibited enhanced enantioselectivity for the resolution of allylic alcohol to the corresponding optically active (S)‐allylic alcohol and (R)‐allylic alcohol acetate compared to free PSL. The enantiomeric excess of (S)‐l‐pheny‐2‐propen‐1‐ol for the former (98.1%) was 81.7 times that of the latter (1.2%) when the immobilized PSL was used for transesterification resolution of (R,S)‐l‐pheny‐2‐propen‐1‐ol. Furthermore, the ees and eep values were still retained at 95.2% and 95.4% after PSL/Fe3O4@GEM was recycled 10 times, indicating that PSL/Fe3O4@GEM had very good reusability. In addition, the transesterification resolution of (R,S)‐1‐(4‐methylphenyl)‐2‐propen‐1‐ol and (R,S)‐1‐(4‐bromophenyl)‐2‐propen‐1‐ol was catalyzed by PSL/Fe3O4@GEM, affording ideal ees and eep values of 99.3%, 97.4% and 99.6%, 98.2%, respectively. Therefore, PSL/Fe3O4@GEM demonstrated its potential as a highly efficient enzymatic reactor and Fe3O4@GEM would be very promising carriers for immobilizing enzymes in industrial application. 相似文献
997.
998.
Present paper reports the synthesis of multiferroic composite (1-x) [Ba0.8Sr0.2Ti)O3]-x[Co0.9Ni0.1Fe2O4] were x = 0.1, 0.2, 0.3 and 0.4. Both phases of the composite i.e. ferroelectric (BST) and ferrite (CNFO) are synthesized via hydroxide co-precipitation method followed by microwave sintering technique at 1100 °C. These composites were characterized for their structural, microstructural, dielectric analysis, magnetodielectric (MD) effect and ferroelectric properties. Presence of both the phases ferroelectric (BST) and ferromagnetic (CNFO) are confirmed by the x-ray diffraction and scanning electron microscopic analysis. Maxwell-Wagner type dielectric dispersion is observed in frequency dependent dielectric measurement. Temperature-dependent dielectric properties were measured from 25 °C to 500 °C at various applied frequencies. Ferroelectric behavior in the composites was confirmed by the polarization vs. Electric field analysis. The magnetodielectric effect was studied in the presence of applied magnetic field from 0 to 1 Tesla. Magnetocapacitance (%) increases with increase in the ferrite concentration in the ferroelectric phase. The maximum percentage of magnetocapacitance is observed in 60BST-40CNFO composite which is MC = 30% at the frequency 1 KHz with the applied magnetic field is 1-Tesla. Room temperature magnetic hysteresis loops show an increase in saturation magnetization (Ms) with an increase in ferrite concentration. 相似文献
999.
The rare earth-rich intermetallic phases RE9TMg4 (RE = Y, Dy-Tm, Lu; T = Ru, Rh, Os, Ir) were synthesized by induction melting of the elements using sealed niobium ampoules as crucible material. The melted samples were additionally annealed in muffle furnaces and subsequently characterized by X-ray powder diffraction. The RE9TMg4 compounds adopt an ordered Co2Al5 type structure, space group P63/mmc. Four structures were refined from single-crystal X-ray diffractometer data: a = 953.71(5), c = 968.41(5) pm, wR2 = 0.00273, 603 F2 values, 21 parameters for Tm8.76RuMg4.24; a = 958.37(5), c = 975.66(5), wR2 = 0.00384, 661 F2 values, 20 parameters for Dy9OsMg4; a = 943.70(5), c = 967.91(5) pm, wR2 = 0.00430, 592 F2 values, 21 parameters for Tm8.74OsMg4.26; a = 968.09(5), c = 978.25(5) pm, wR2 = 0.0439, 623 F2 values, 21 parameters for Y9.18IrMg3.82. The compounds are prone to small homogeneity ranges (RE/Mg mixing). The transition metal atoms have tricapped trigonal prismatic rare earth coordination. These T@RE9 units (TP) are condensed with empty RE6 octahedra (O) via common triangular faces forming infinite strands with a sequence –TP–O–O–. These strands show the motif of hexagonal rod packing and they are separated by chains of edge- and corner-sharing tetrahedra. The magnesium substructures in the hexagonal Laves phase YMg2 and the prototype Y9CoMg4 are structurally closely related. Charge transfer trends, electronic band structures and bonding properties were studied within DFT. The resulting picture is that cobalt brings covalent character by reducing the overall charge transfer and modifies the Laves phase YMg2 by providing larger localization in the density of states. The Y–Co bonding in Y9CoMg4 prevails while weakening the Y–Mg bonds. The investigations of the magnetic properties of selected RE9TMg4 compounds revealed Pauli paramagnetic behavior for Y9CoMg4, Y9OsMg4 and Y9IrMg4. A ferromagnetic ground state with Curie temperatures of 46.0 and 47.6 K was observed for Dy9RuMg4 and Dy9OsMg4, respectively. Ho9RuMg4, Ho9OsMg4 and Tm9OsMg4 reveal antiferromagnetic ordering with Neél temperatures below 20 K. 相似文献
1000.
The feasibility of modulating dopant segregation using rotation for floating-zone silicon growth in axisymmetric magnetic fields is investigated through computer simulation. In the model, heat and mass transfer, fluid flow, magnetic fields, melt/solid interfaces, and the free surface are solved globally by a robust finte-volume/Newton's method. Different rotation modes, single- and counter-rotations, are applied to the growth under both axial and cusp magnetic fields. Under the magnetic fields, it is observed that dopant mixing is poor in the quiescent core region of the molten zone, and the weak convection there is responsible for the segregation. Under an axial magnetic field, moderate counter-rotation or crystal rotation improves dopant uniformity. However, excess counter-rotation or feed rotation alone results in more complicated flow structures, and thus induces larger radial segregation. For the cusp fields, rotation can enhance more easily the dopant mixing in the core melt and thus improve dopant uniformity. 相似文献