ben Li

Effect of Pr substitution on structural and dielectric properties of SrTiO3

Pr-doped SrTiO3 ceramics were fabricated by the conventional solid-state reaction method. Pr-doping greatly decreased the lattice parameters and the average grain size of SrTiO3 ceramics sample. Two thermally activated dielectric relaxations were found for the low- and high-temperature relaxations, respectively. By means of a detailed analysis, the low-temperature relaxation was ascribed to the electric hopping between Pr3+ and Pr4+ induced by the Pr-doping, and the origin of the high-temperature relaxation was changed from oxygen vacancies to the polar nanoregions with the increase of Pr content.

Thickness-dependent structural and magnetic properties of BiFeO3 films prepared by metal organic decomposition method

Perovskite BiFeO3 films with various thicknesses were prepared on Pt/Ti/SiO2/Si substrates by metal organic decomposition method. It was found that, with the film thickness increasing from 35 to 120 nm, the grain and ferroelectric domain size slightly increased, while the saturation magnetization Ms abruptly decreased. For the further increase of film thickness, Ms decreased slowly and the magnetization of unit area exhibited a fluctuation behavior. Moreover, the magnetic anisotropy degenerated with the increase of film thickness. The possible causes for the thickness effects were discussed.

Synthesis of TiO2@g-C3N4 core-shell nanorod arrays with Z-scheme enhanced photocatalytic activity under visible light

Novel rutile TiO2@g-C3N4 core-shell photocatalysts were synthesized by a facile saturated aqueous solution method. The composites were further characterized by using X-ray diffraction (XRD), high-resolution transmission microscopy (HRTEM), UV-visible light diffusion reflectance spectrometry (DRS), X-ray photoelectron spectroscopy (XPS) and so on. The results indicated that an ultrathin layer of g-C3N4 was in-situ fabricated over the surface of rutile TiO2 nanorod. The rutile TiO2@ g-C3N4 core-shell structures showed much higher photo-current and photocatalytic activity for Rhodamine B (RhB) degradation under visible irradiation. The enhanced performance was attributed to the high separation efficiency of photo-induced carriers via a Z-scheme form.

Spin polarized current through Cu-DNA modulated by a gate voltage

Spin polarized current through DNA molecule doped with one Cu2+ ion is studied. It is found that the spin polarization is sensitive to the position of the Cu2+ ion doping. In order to obtain a steady and large spin polarization, the metal ion should be doped at the end of the DNA molecule. We propose the possibility of controlling the spin polarization using a gate voltage. This control is originated from electron precession, which is induced by Rashba spin-orbit coupling.

Effect of SiO2 on the Varistor and Dielectric Properties of SnO2-Zn2SnO4 Ceramic Composites

ABSTRACT SnO2-Zn2SnO4 ceramic composites are prepared by traditional ceramics processing and the effect of SiO2 on the varistor, dielectric properties has been investigated. With increasing SiO2 content to 0.2 mol%, the nonlinear coefficient α and the breakdown electrical field E1.0 gets to the maximum of 7.7 and minimum of 12V.mm–1, respectively. Meanwhile, the dielectric spectra show that the sample doped with 0.2 mol% SiO2 has the highest relative permittivity εr of ∼7×103 at 40 Hz, 40°C. The dielectric temperature spectra show that the temperature stability of the dielectric properties can be improved by doping 0.2 mol% SiO2. The good properties indicate that SiO2 doped SnO2-Zn2SnO4 ceramic composites are viable candidate for capacitor-varistor functional devices to protect electrical micro-machines. Further studies show that the density and grain uniformity of the composites are improved by doping proper content of SiO2. The compact and uniform microstructure may be responsible for the excellent varistor and dielectric properties. GRAPHICAL ABSTRACT

Quantum critical points in tunneling junction of topological superconductor and topological insulator

Abstract The tunneling junction between one-dimensional topological superconductor and integer (fractional) topological insulator (TI), realized via point contact, is investigated theoretically with bosonization technology and renormalization group methods. For the integer TI case, in a finite range of edge interaction parameter, there is a non-trivial stable fixed point which corresponds to the physical picture that the edge of TI breaks up into two sections at the junction, with one side coupling strongly to the Majorana fermion and exhibiting perfect Andreev reflection, while the other side decouples, exhibiting perfect normal reflection at low energies. This fixed point can be used as a signature of the Majorana fermion and tested by nowadays experiment techniques. For the fractional TI case, the universal low-energy transport properties are described by perfect normal reflection, perfect Andreev reflection, or perfect insulating fixed points dependent on the filling fraction and edge interaction parameter of fractional TI.

Combination of conductive filaments and Schottky behavior in multifunctional Sn1−xCuxO2−δ memristor

Resistive switching behaviors of SnO2 films are largely improved by Cu acceptor doping. At a suitable Cu2+ concentration, a high ON/OFF resistance ratio (104), good endurance (104) and long retention (104 s) are achieved in the Cu/SnO2:Cu/Pt sandwich structure with the modulation of carriers and oxygen vacancies. As a memristor, the resistive switching can be triggered by one pulse or a train of pulses, and the latter mode could simulate the long-term potentiation of biological synapses. Moreover, the multi-resistance states during the reset process demonstrate a combination of abrupt and incremental resistive switching. The peculiar conductive behavior of the devices is considered to result from the cooperation of conductive filaments and Schottky barrier, with the oxygen vacancies serving as the bridge. These studies are significant for higher density storage and cognitive computing in future.

Docking accuracy enhanced by QM-derived protein charges

ABSTRACT Effects of protein polari sation on docking accuracy were investigated using molecular docking programme AutoDock 4 in which topology-specific empirical Gasteiger charges were replaced with Polarised protein-specific charges (PPC) to represent quantum mechanics- polarised protein. Docking was successfully conducted for 50 diverse protein–ligand complexes. The docking with PPC charges shows a decrease in the root-mean-square deviation (RMSD) values of ligands compared to those from the docking with Gasteiger charges. Ligand binding orientations and their key interactions such as hydrogen bonding interactions in X-ray structures were substantially reproduced in complexes docked using PPC scheme with 98% of the RMSDs of the best docking poses less than 2 Å compared to 74% in the docking with Gasteiger charges. Considerable improvements in docking accuracy were observed by simply altering the atomic partial charges in the scoring function, which reflects the importance of protein polarisation in molecular docking. Further research can be carried out to (1) include polarisation of both ligands and proteins to account for polarisation effects within protein and between protein and ligand, and (2) develop a PPC-based scoring function to increase the docking accuracies for protein–ligand complexes from a larger variety of protein families.

Effect of impurity content on structure of living water

In order to study the influence of impurities content on the water structure, Raman spectra and degrees of depolarization of different living water are measured by Raman spectroscopy, the relationship between the depolarization ratio and the impurity content in drinking water was obtained by the utilisation of computer deconvolution for the stretching vibration peak. The results showed that the intensity of different bending vibration is almost the same, and the intensity of the stretching vibration reflects different content of impurities in water. Depolarization calculation of water molecules showed that the stretching vibration is stronger than the bending vibration. The interaction of impurity ions and water molecules enhances the vibration rate of water molecules, making the symmetry of stretching vibration reduced, and leading to increased depolarization ratio. Therefore, the impurities content can be determined from the relative intensity of Raman characteristic peaks and the degrees of depolarization.

Experimental study of liquid refractive index sensing based on a U-shaped optical fiber

A U-shaped optical fiber sensing system designed to measure the refractive index of liquid had been proposed. The sensing mechanism of U-shaped optical fiber was discussed. A general single-mode fiber was bent into U-shaped and partially cladding of U-shaped fiber was corroded by HF acid buffer solution. Powers of different diameters of U-shaped fibers had been measured by many experiments. The results showed that the diameter of U-shaped fiber cladding 40 μm and the diameter of U-shaped was 1 cm were suitable to measure liquid refractive index. Then, this U-shaped optical fiber was immersed in liquid, such as pure water, ethanol, acetone and isopropanol, respectively. The evanescent field of the U-shaped fiber should be modulated by the liquid. The optical signal in the U-shaped fiber was measured with the optical spectrum analyzers(OSA). Finally, the experimental results were analyzed, and the spectra in the air was selected as a reference. The relative intensity was obtained for the different liquid. These results showed that the relative intensity of the liquid had a good linear relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low cost, and it can also be applied in measuring the level of liquid.