Low-energy(40 keV) proton irradiation of YBa_2Cu_3O_(7-x) thin films:Micro-Raman characterization and electrical transport properties

To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa_2Cu_3O_(7-x)(YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO_2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TCwith the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TC_0 is not observed at a fluence of 10^(15)p/cm^2.Furthermore, the variation of activation energy U_0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.

Oxygen vacancy in N-doped Cu_2 O crystals:A density functional theory study

The N-doping effects on the electronic properties of Cu2O crystals are investigated using density functional theory. The calculated results show that N-doped Cu2O with or without oxygen vacancy exhibits different modifications of electronic band structure. In N anion-doped Cu2O, some N 2p states overlap and mix with the O 2p valence band, leading to a slight narrowing of band gap compared with the undoped Cu2O. However, it is found that the coexistence of both N impurity and oxygen vacancy contributes to band gap widening which may account for the experimentally observed optical band gap widening by N doping.

O3 fast and simple treatment-enhanced p-doped in Spiro-MeOTAD for CH3NH3I vapor-assisted processed CH3NH3PbI3 perovskite solar cells

We demonstrate a simple and fast post-deposition treatment with high process compatibility on the hole transport material（HTM） Spiro-MeOTAD in vapor-assisted solution processed methylammonium lead triiodide（CH3NH3PbI3）-based solar cells. The prepared Co-doped p-type Spiro-MeOTAD films are treated by O3 at room temperature for 5 min,10 min, and 20 min, respectively, prior to the deposition of the metal electrodes. Compared with the traditional oxidation of Spiro-MeOTAD films overnight in dry air, our fast O3 treatment of HTM at room temperature only needs just 10 min,and a relative 40.3% increment in the power conversion efficiency is observed with respect to the result of without-treated perovskite solar cells. This improvement of efficiency is mainly attributed to the obvious increase of the fill factor and short-circuit current density, despite a slight decrease in the open-circuit voltage. Ultraviolet photoelectron spectroscopy（UPS） and Hall effect measurement method are employed in our study to determine the changes of properties after O3 treatment in HTM. It is found that after the HTM is exposed to O3, its p-type doping level is enhanced. The enhancement of conductivity and Hall mobility of the film, resulting from the improvement in p-doping level of HTM, leads to better performances of perovskite solar cells. Best power conversion efficiencies（PCEs） of 13.05% and 16.39% are achieved with most properly optimized HTM via CH3NH3I vapor-assisted method and traditional single-step method respectively.

A density functional theory study on the adsorption of CO and O_2 on Cu-terminated Cu_2O(111) surface

The adsorptions of CO and 02 molecules individually on the stoichiometric Cu-terminatcd Cu20 （111） surface are investigated by first-principles calculations on the basis of the density functional theory. The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of-1.69 eV, whereas the 02 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cul site, and has an adsorption energy of -1.97 eV. From the analysis of density of states, it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate. The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption, and overlaps substantially with bands of the adsorbed CO molecule. There is a broadening of the 2π orbital of the 02 molecule because of its overlapping with the Cu 3d orbital, indicating that strong 3d-2π interactions are involved in the chemisorption of the 02 molecule on the surface.

Ultraviolet light A irradiation induces immunosuppression associated with the generation of reactive oxygen species in human neutrophils

Ultraviolet blood irradiation has been used as a physical therapy to treat many nonspeci¯c diseases in clinics;however,the underlying mechanisms remain largely unclear.Neutrophils,the first line of host defense,play a crucial role in a variety of in°ammatory responses.In the present work,we investigated the effects of ultraviolet light A(UVA)on the immune functions of human neutrophils at the single-cell level by using an inverted°uorescence microscope.N-Formylmethionyl-leucyl-phenylalanine(FMLP),a classic physiological chemotactic peptide,was used to induce a series of immune responses in neutrophils in vitro.FMLP-induced calcium mobilization,migration,and phagocytosis in human neutrophils was significantly blocked after treatment with 365 nm UVA irradiation,demonstrating the immunosuppressive effects of UVA irradiation on neutrophils.Similar responses were also observed when the cells were pretreated with H2O2,a type of reactive oxygen species(ROS).Furthermore,UVA irradiation resulted in an increase in NAD(P)H,a member of host oxidative stress in cells.Taken together,our data indicate that UVA irradiation results in immunosuppression associated with the production of ROS in human neutrophils.

Variable optical chirality in atomic assisted microcavity

The manipulating of optical waves in a microcavity is essential to developing the integrated optical devices.Generally,the two eigenmodes in a whispering-gallery-mode(WGM)microcavity possess chiral symmetry.Here we show the chiral symmetry breaking is induced by the asymmetric backscattering of counter-propagating optical waves in a whisperinggallery-mode(WGM)microcavity with a cavity-made slot filled with atomic vapor.Through tuning the dispersion relation of the atomic vapor in the cavity-made slot,the chiral modes are continuously steered.The mode frequency splitting in the transmission and reflection spectra stem from the chiral symmetry breaking of the two eigenmodes.The displacement sensitivity of the proposed system in response to the length variation of cavity-made slot exhibits a high sensitivity value of 15.22 THz/nm.

s-p orbital hybridization: a strategy for developing efficient photocatalysts with high carrier mobility

Photocatalysis has not only invigorated the field of energy conversion materials,but also is leading to bright prospects for application in the environmental purification field[1].Akira Fujishima and Kenichi Honda[2]first reported photocatalytic water splitting on a Ti O2semiconductor electrode under ultraviolet(UV)light in1972.In semiconductor photocatalysts,electrons are excited from valence band maximum(VBM)to conduction band

MnⅡ掺杂二维杂化钙钛矿（C4H9NH3）2PbCl4的机械力化学合成及其发光性能研究（英文）

简单和高效的机械力化学合成方法在先进功能材料的合成领域备受关注.本论文通过机械力化学合成手段,将二价锰离子(MnⅡ)成功掺杂于二维层状钙钛矿(C4H9NH3)2PbCl4中.研究发现,仅通过室温研磨便能观察到二维杂化钙钛矿中,迅速出现MnⅡ的橙红色荧光.其中,掺杂的MnⅡ占据了Pb的格位,其荧光特性源于(C4H9NH3)2Pb1–xMnxCl4的带边发射和MnⅡ的4T1→6A1跃迁之间的能量传递;与此同时,利用第一性原理计算了钙钛矿(C4H9NH3)2Pb1–xMnxCl4掺杂前后的形成能,从理论上证明了具有特殊结构的二维杂化钙钛矿使得Mn2+易于替代Pb2+.鉴于机械力化学合成方法在二维层状钙钛矿中不仅易掺杂且光谱可调的优势,将为新材料领域的进一步开发和应用提供新的机遇.

Investigating the interlayer electron transport and its in?uence on the whole electric properties of black phosphorus

Two-dimensional(2D) nanomaterials have attracted great attention in next generation electronic and optoelectronic technologies due to the unique layered structure and excellent physical and chemical properties. However, the mechanism of transmission along the vertical direction of 2D semiconductor materials has not been investigated. Here, we use first-principles calculations to explore the bandgap energies along different directions, and fabricate a vertical, a lateral and a mixture-structured black phosphorus field effect transistor(BPFET) to study the electrical characteristics along different directions under variable temperatures. The variable temperature test indicates that the mixture-structured device performs more like a lateral device, while the conductance along the vertical direction is hard to be tuned by temperature and electrical field. The unchanged conductance under electric field and variable temperatures allows the vertical device to act as a fixed resistor, promising possible application for the prospective electronic and optoelectronic devices.

Three-dimensional tracking of multiple particles in large depth of field using dual-objective bifocal plane imaging

Tracking moving particles in cells by single particle tracking is an important optical approach widely used in biological research. In order to track multiple particles within a whole cell simultaneously, a parallel tracking approach with large depth of field was put forward. It was based on distorted grating and dual-objective bifocal imaging, making use of the distorted grating to expand the depth of field, dual-objective to gather as many photons as possible, and bifocal plane imaging to realize three-dimensional localization. Simulation of parallel tracking of two particles moving along the z axis demonstrated that even when the two are axially separated by10 μm, they can both be localized simultaneously with transversal precision better than 5 nm and axial precision better than 20 nm.

Tuning the performance of nitrogen reduction reaction by balancing the reactivity of N_(2) and the desorption of NH_(3)

Electrochemical reduction of nitrogen to ammonia under mild conditions provides an intriguing approach for energy conversion. A grand challenge for electrochemical nitrogen reduction reaction (NRR) is to design a superior electrocatalyst to obtain high performance including high catalytic activity and selectivity. In the NRR process, the three most important steps are nitrogen adsorption, nitrogen activation, and ammonia desorption. We take MoS_(2) as the research object and obtain catalysts with different electronic densities of states through the doping of Fe and V, respectively. Using a combination of experiments and theoretical calculations, it is demonstrated that V-doped MoS_(2) (MoS_(2)-V) shows better nitrogen adsorption and activation, while Fe-doped MoS_(2) (MoS_(2)-Fe) obtains the highest ammonia yield in experiments (20.11 µg·h^(−1)·mg^(−1)cat.) due to its easier desorption of ammonia. Therefore, an appropriate balance between nitrogen adsorption, nitrogen activation, and ammonia desorption should be achieved to obtain highly efficient NRR electrocatalysts.

Simulation of effects of incident beam condition in p-p elastic scattering

The simulation is performed for the monitors of beam direction and beam position for p-p elastic scattering. We set several variables to simulate the monitors of incident beam condition changes： beam positions at the quadrupole magnet and target in beam line polarimeter（BLP2）, distance between quadrupole magnet and target,size of plastic scintillators, distance between the target in BLP2 and the centers of plastic scintillators, and beam polarization. Through the rotation of the coordinate system, the distributions of scattered and recoiled protons in the laboratory system were obtained. By analyzing the count yields in plastic scintillators at di？erent beam positions,we found that the beam incident angular change（0.35°） could be detected when the asymmetry of geometries of left and right scintillators in BLP2 was changed by 6%. Therefore, the scattering angle measured in the experiment can be tracked by these monitors.