时间：   2017年12月4日（星期一）下午14:30

题目：Large magneto-optical effects in hole-doped blue phosphorene and gray arsenene

报告人：周小东         指导教师：冯万祥

Abstract ：Blue phosphorene (BP) and gray arsenene (GA), consisting of phosphorus and arsenic atoms in two-dimensional (2D) low-buckled honeycomb lattices, respectively, have received great interest because of their excellent electronic and optoelectronic performances. Here, using first-principles density functional theory, we investigate magneto-optical (MO) Kerr and Faraday effects in BP and GA under hole doping.Ferromagnetic ground states are found in hole-doped monolayer and bilayer BP and GA due to the Stoner electronic instability, which originates from the van Hove singularity of the density of states at the valence band edge. The Kerr and Faraday effects strongly depend on the doping concentration and therefore are electrically controllable by adjusting the number of holes via the gate voltage. The influences of the thin film thickness, spin-polarized direction, and the substrate on the MO effects are further studied. We find that the MO effects are weakened remarkably as the thin film thickness increases and can be negligible more than three single-layers; the MO effects are much more prominent when spin polarization is along the out-of-plane direction and will decrease more than one order of magnitude on turning the spin in the crystal plane; the insulating substrates with small refractive indices are favorable to generate large MO effects and appropriate compressive strains applied on BP and GA due to lattice mismatch with substrates are further beneficial.The MO effects in GA are generally larger than those in BP because the strength of spin–orbit coupling in the arsenic atom is larger than that in the phosphorus atom. Monolayer GA possesses the largest Kerr and Faraday rotation angles, which are comparable to or even larger than those of well-known MO materials such as 3d-transition-metal multilayers and compounds. Our results indicate that BP and GA are a promising material platform for MO device applications.

题  目：Effects of oxygen/argon pressure ratio on the structural and optical properties of Mn-doped ZnO thin films prepared by magnetron co-sputtering

报告人：索晓霞                指导老师： 王志

Abstract：Manganese doped ZnO (ZnO:Mn) thin films were deposited by magnetron co-sputtering with different oxygen/argon pressure ratio r. The influence of r on the structural, surface morphology and optical properties of the films was studied. A preferential growth along c axis was found in all films. As r increases, lattice constant c and compressive stress σ increase. For ZnO:Mn thin films, the absorption edge shifts toward the shorter wavelength with r increasing, and the optical band gap is narrowed by low r values. the resistivity of the films is also reduced by low oxygen partial.

题  目：大气压等离子体射流的特性及其在细胞保护中的应用

报告人：孟昭忠                 指导老师：欧阳吉庭

Abstract：Atmospheric pressure plasma jet has recently emerged as an effective tool in the field of “plasma medicine” due to its several advantages including easy operation, high reaction efficiency, environmental friendly, low gas temperature, amenability to temperature-sensitive material, and so on. According to previous studies, the neuroprotective effects of APPJ have been discovered against oxidative stress-induced injuries on SH-SY5Y cells, which was related to the APPJ-induced nitric oxide (NO) accumulation. However, the effects of APPJ on other injuries have not been reported. In this thesis, AC-driven He-APPJ is used on hypoxic injured neurons. after investigation of cell viability, cell morphology and the content of NO and ROS, we explain the protection mechanism of APPJ on hypoxia induced SH-SY5Y cells. The physical properties, discharge characteristics and development process of the jet are also investigated. There include two parts of experimental works in this thesis.

First, the characteristics of atmospheric pressure plasma jet are measured. The development of plasma jet head is recorded by ICCD. The velocity of jet development under different applied voltage and power frequency is calculated accordingly. The results show that the jet speed would be faster and the maximum speed would increase with the increase of voltage and power frequency. The influences of discharge parameters on the jet characteristics are studied. The jet length increases with increasing voltage and flow rates, applied voltage and gas flow are the key factors that affect the jet length. But the jet length remains constant at different frequencies. NO emission spectrum shows that the highest intensity appears at the nozzle exit. The intensity weakens with the increase of distance from the nozzle. There exists a linear relationship between NO intensity values and power frequency and gas flow rates. However, relationship between the NO intensity and the applied voltage is uncertain.

Second, the application of atmospheric pressure plasma jet in cell protection experiment is tested. SH-SY5Y cells are adherently cultured, and then treated with APPJ for different times. Subsequently, cells are cultured in hypoxia for 5 hours and under anoxic condition for 24 hours. Related parameters are tested by various methods, including the cell morphology changes in real time by ECIS, cell apoptosis by LDH assay, the content of NO by Griess kit, and the content of ROS by Hydrogen Peroxide Assay Kit. It is shown that cells proliferate significantly after 20 hours hypoxia treatment, which could be inhibited by the 30 s APPJ treatment. After 24 hours hypoxia, cells membrane deformation and cells contract severely. Cell morphology could be improved by the APPJ treatment, after 24 hours hypoxic exposure. The NO concentration increases significantly with the duration of APPJ treatment. It indicates that APPJ could protect SH-SY5Y cells from hypoxia-induced injuries, which may relate with NO accumulation.