Microwave synthesis and phase transitions in nanoscale BiFeO<Subscript>3</Subscript>

Nanosized multiferroic BiFeO₃ powders were synthesized by a microwave combustion method. The average crystallite sizes of the samples stay at a same level with the ratio of fuel glycine 0.5 ≤ G/N ≤ 1.5 and it increases significantly with G/N = 2.0. An inhomogeneity of amorphous and microcrystallites is observed directly by HRTEM. A ferromagnetic hysteresis loop with a saturation magnetization (M _S) of ~0.09 μ _B /Fe has been observed at room temperature in the sample with a crystallite size of 53 nm, whereas other powders with much smaller crystallite size (~20 nm) will not saturate even at 20 kOe. These magnetic behaviors were ascribed to a combination of the magnetic enhancement effect of a decreased crystallite size and superparamagnetic mechanism.     

Particle-core coupling in141Nd

High-spin states in¹⁴¹Nd have been studied using in-beam γ-ray spectroscopic techniques via the¹³⁰Te(¹⁶O, 5nγ)¹⁴¹Nd reaction. The level scheme of¹⁴¹Nd has been extended up to an excitation energy of 7614.5 keV including 12 new γ rays deexciting 15 new levels. According to particle-vibrator coupling and semi-empirical shell model calculations, the level structure of¹⁴¹Nd can be well interpreted by coupling an h_11/2 neutron-hole to the respective excited states in¹⁴²Nd core.     

Phase separation in the spin-state transition system of La1−xBaxCoO3

The magnetic and electric transport properties of La_1−xBa_xCoO₃ (0<x≤0.50) have been studied systematically. Two effects of substitution divalent ions on the spin-state transition of Co³⁺ have been differentiated for the substitution of Ba²⁺ for La³⁺ in La_1−xBa_xCoO₃. The first is the transition from low-spin state to high-spin state due to lattice expansion, and the second is the transition from low-spin state to intermediate-spin state caused by the strong hybridization between ligand (oxygen) 2p and Co 3d orbital with introduction of holes in the oxygen 2p orbital. Based on the two different spin-state transition mechanisms and experimental results, a phase separation model has been developed and a very detailed magnetic and electric phase diagram of La_1−xBa_xCoO₃ has been constructed.     

Ionic size effect on magnetic and electronic properties of La0.70A0.05Sr0.25CoO3 (A=La,Nd, Gd,Ho, Y)

The structural, magnetic and electronic transport properties of La_0.70A_0.05Sr_0.25CoO₃ (A=La, Nd, Gd, Ho, Y) have been investigated by X-ray diffraction and the magnetization and resistivity measurements. All the samples crystallize into hexagonal lattice with the space group R-3C (A167) at room temperature. Small doped ions shrink the lattices almost linearly and isotropically, and bend the Co–O–Co bond angle. Although the Co atoms in all compounds are stabilized in intermediate-spin electronic configuration, the (residual) resistivity (T→0$T\to 0$) increase significantly with doping of the small ions. At low temperatures, the compounds change from metallic state of La_0.70A_0.05Sr_0.25CoO₃ (A=La, Nd, Gd) to insulated state of La_0.70A_0.05Sr_0.25CoO₃ (A=Ho, Y). The 5–7% magnetoresistance (MR) near Curie temperature can be interpreted in terms of the external field suppression of the spin fluctuation, but the relative large MR in the insulator state of La_0.70A_0.05Sr_0.25CoO₃ (A=Ho, Y) (∼20% up to 50-kOe field at 5 K) probably results from the field-induced transfer integral and the tunneling effect.     

An improved microbond test method for determination of the interfacial shear strength between carbon fibers and epoxy resin

An improved microbond method, with a corresponding testing device, was developed to measure the interfacial shear strength (IFSS) between carbon fibers and epoxy resin. Compared to other methods, this proposed approach is both highly efficient and easy to operate. As a case study for this new method, we measured the IFSS between carbon fibers and epoxy resin. Although the average IFSS obtained was only 7.08 MPa, which is much lower than values documented in several previous studies, the displacement-load curves demonstrate the strong reliability of this method. The lower IFSS could be explained by the highly inert surface of the carbon fibers, which was highly graphitized and had no sizing treatment. Therefore, this method has high potential in applications for screening the sizing agents of carbon fibers or optimizing the surface sizing processes.     

Shape co-existence and structural evolution of thevi13/2 band in157Yb

The high-spin states of¹⁵⁷Yb have been studied via the reaction of¹⁴⁴Sm(¹⁶O, 3n) at¹⁶O energy of 90 MeV using techniques of in-beam γ-ray spectroscopy. Measurement of γ-γ-t coincidences was performed with 11 BGO(AC)HPGe detectors. Based on the γ-γ coincidence relationships and the measured results of γ-ray anisotropies and DCO ratios, the level scheme for¹⁵⁷Yb was established. The shape co-existence and structural evolution of thevi_13/2 band with increasing angular momentum in¹⁵⁷Yb have been discussed. The systematics of thevi_13/2 bands in theN=87 odd-A isotones have been compared.     

Studies of the Interaction Between Ronidazole and Human Serum Albumin by Spectroscopic and Molecular Docking Methods

Ronidazole (RNZ) is widely used for the therapeutic treatment of farmed animals and is suspected of being a human carcinogen and mutagen. The interaction between RNZ and human serum albumin (HSA) was investigated systematically by fluorescence spectroscopy, synchronous fluorescence, three-dimensional fluorescence, CD spectroscopy, UV–vis absorption spectroscopy and a molecular docking study. The results indicate that the probable quenching mechanism of HSA by RNZ is dynamic quenching. The corresponding thermodynamic parameters, such as ΔH, ΔS and ΔG, etc., were calculated according to the van’t Hoff equation. The results indicate that the forces acting between RNZ and HSA are mainly hydrogen bonds and van der Waals forces. The conformational changes in the interaction were studied by synchronous fluorescence, CD spectroscopy and three-dimensional fluorescence spectra. The results reveal that the microenvironment and conformation of HSA has been changed. A molecular modeling study further confirmed the binding mode obtained by the experimental studies.     

Synthesis,Crystal Structure and DNA-Binding Study of a New Zinc(II) Complex Based on 2,6-Bis(imino)pyridyl Ligand

A new zinc complex [Zn(L1)Cl₂]₂?CH₃OH?2H₂O (complex 1), where L1 stands for 2,6-Bis{[(4-ethylphenyl)imino]ethyl}pyridine (L1) has been synthesized and characterized. The crystal structure of L1 and complex 1 have been determined by single-crystal X-ray diffraction. Both compounds crystallize in the monoclinic P2₁/c space group. For the ligand L1, the crystal parameters are a?=?16.7487(7) Å, b?=?5.8177(3) Å, c?=?21.8427(10) Å, β?=?104.1350(10)° and Z?=?4. For complex 1, the crystal parameters are a?=?8.0216(14) Å, b?=?13.433(2) Å, c?=?24.640(4) Å, β?=?90.223(3)° and Z?=?2. In the crystal structure of complex 1, L1 acts as a tridentate ligand and coordinated with Zn1 with three nitrogen atoms. Together with two chlorine atoms, Zn1 atom is five-coordinated in a trigonal bipyramidal geometry. Hydrogen bonds play great role in the crystal structure of complex 1 and form a two-dimensional network. Furthermore, the DNA-binding property of complex 1 with fish sperm DNA (FS-DNA) has been investigated by electronic absorption titration. The result suggests that complex 1 might interact with FS-DNA via groove binding mode.

Graphical abstract

The single crystals of 2,6-Bis{[(4-ethylphenyl)imino]ethyl}pyridine (L1) and it’s Zinc(II) complex [Zn(L1)Cl₂]?CH₃OH?H₂O (1) were determined. In the crystal structure of complex 1, Zn1 atom is five-coordinated in a trigonal bipyramidal geometry. A two-dimensional network is formed by hydrogen bonds. DNA-binding study indicated that complex 1 interact with FS-DNA via groove binding mode.

     

Superparamagnetic properties of La1−xBaxCoO3 (0.0<x<0.18)

The static and dynamic magnetic properties of La_1−xBa_xCoO₃ (0<x<0.18) (LBCO) have been investigated by the dc and ac susceptibility measurements systematically. The spin-glass-like characteristics of magnetic behavior, which are always considered as an evidence of spin glasses for La_1−xSr_xCoO₃ (0<x<0.18) (LSCO), have been observed. However, just like that of LSCO, some magnetic behaviors, which are different from the canonical spin-glass characteristics, for example, the difference far above peak temperature T_p of zero-field-cooled curve between field-cooled magnetization (FCM) and zero-FCM (ZFCM) and the very broad peaks in the samples for x>0.10, are also observed simultaneously. Based on the comparisons with canonical spin-glass Au₉₆Fe₄ alloy and conventional superparamagnetic (SPM) Cu₉₇Co₃ alloy, the nature of the magnetic behaviors in LBCO is ascribed to the superparamagnetic cluster rather than spin glass. Though the magnetic properties behave as SPM, LBCO has one critical point different from that of the conventional SPM Cu₉₇Co₃ alloy. The segregated Co nanoparticles in the Cu₉₇Co₃ alloy are isolated by nonmagnetic background while the clusters in LBCO are embedded in an antiferromagnetic matrix. The SPM behavior of LBCO can only exist at low temperature because the antiferromagnetic matrix transfers to paramagnetic phase at Neél temperature T_N and the SPM cluster turns into ferromagnetic (FM) above T_N.