铁原子吸附联苯烯单层电子结构的第一性原理

联苯烯单层由碳原子的四元、六元和八元环组成,具有与石墨烯相似的单原子层结构.2021年5月,Science首次报道了该材料的实验合成,引起了科研工作者的极大关注.基于第一性原理的密度泛函方法,研究了铁原子在联苯烯单层的吸附构型并分析了其电子结构.结构优化、吸附能和分子动力学的计算表明,联苯烯单层的四元环空位是铁原子最稳定的吸附位点,吸附能可达1.56 eV.电子态密度计算表明铁3d电子与碳的2p电子有较强的轨道杂化,同时电荷转移计算显示铁原子向近邻碳原子转移的电荷约为0.73个电子,说明联苯烯单层与吸附的铁原子之间形成了稳定的化学键.另外,铁原子吸附于联苯烯单层后体系显磁性,铁原子上局域磁矩大小约为1.81μB,方向指向面外.因此,本文确认了联苯烯单层是比石墨烯更好的铁原子吸附载体且体系有磁性,这为研究吸附材料的电磁、输运、催化等特性提供了新的平台.     

The film thickness dependent thermal stability of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>:Ag thin films as high-temperature solar selective absorbers

The monolayer Al₂O₃:Ag thin films were prepared by magnetron sputtering. The microstructure and optical properties of thin film after annealing at 700 °C in air were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and spectrophotometer. It revealed that the particle shape, size, and distribution across the film were greatly changed before and after annealing. The surface plasmon resonance absorption and thermal stability of the film were found to be strongly dependent on the film thickness, which was believed to be associated with the evolution process of particle diffusion, agglomeration, and evaporation during annealing at high temperature. When the film thickness was smaller than 90 nm, the film SPR absorption can be attenuated until extinct with increasing annealing time due to the evaporation of Ag particles. While the film thickness was larger than 120 nm, the absorption can keep constant even after annealing for 64 h due to the agglomeration of Ag particles. On the base of film thickness results, the multilayer Al₂O₃:Ag solar selective thin films were prepared and the thermal stability test illustrated that the solar selectivity of multilayer films with absorbing layer thickness larger than 120 nm did not degrade after annealing at 500 °C for 70 h in air. It can be concluded that film thickness is an important factor to control the thermal stability of Al₂O₃:Ag thin films as high-temperature solar selective absorbers.     

Preparation and characterization of spinel Li4Ti5O12 nanoparticles anode materials for lithium ion battery

Spinel Li₄Ti₅O₁₂ nanoparticles were prepared via a high-temperature solid-state reaction by adding the prepared cellulose to an aqueous dispersion of lithium salts and titanium dioxide. The precursors of Li₄Ti₅O₁₂ were characterized by thermogravimetry and differential scanning calorimetry. The obtained Li₄Ti₅O₁₂ nanoparticles were characterized using X-ray diffraction, transmission electron microscopy (TEM) and electrochemical measurements. The TEM revealed that the Li₄Ti₅O₁₂ prepared with cellulose is composed of nanoparticles with an average particle diameter of 20–30 nm. Galvanostatic battery testing showed that nano-sized Li₄Ti₅O₁₂ exhibit better electrochemical properties than submicro-sized Li₄Ti₅O₁₂ do especially at high current rates, which can deliver a reversible discharge capacity of 131 mAh g⁻¹ at the rate of 10 C, whereas that of the submicro-sized sample decreases to 25 mAh g⁻¹ at the same rate (10 C). Its reversible capacity is maintained at ~172.2 mAh g⁻¹ with the voltage range 1.0–3.0 V (vs. Li) at the current rate of 0.5 C for over 80 cycles.     

Stable dual-wavelength single-longitudinal-mode ring erbium-doped fiber laser for optical generation of microwave frequency

We demonstrate a simple dual-wavelength ring erbium-doped fiber laser operating in single-longitudinal-mode (SLM) at room temperature. A pair of reflection type short-period fiber Bragg gratings (FBGs), which have two different center wavelengths of 1545.072 and 1545.284 nm, are used as the wavelength-selective component of the laser. A segment of unpumped polarization maintaining erbium-doped fiber (PM-EDF) is acted as a narrow multiband filter. By turning the polarization controller (PC) to enhance the polarization hole burning (PHB), the single-wavelength and dual-wavelength laser oscillations are observed at 1545.072 and 1545.284 nm. The output power variation is less than 0.6 dB for both wavelengths over a five-minute period and the optical signal to noise ratio (OSNR) is greater than 50 dB. By beating the dual-wavelengths at a photodetector (PD), a microwave signal at 26.44 GHz is demonstrated.     

Human‐Serum‐Albumin‐Coated Prussian Blue Nanoparticles as pH‐/Thermotriggered Drug‐Delivery Vehicles for Cancer Thermochemotherapy

Constructing novel multimodal antitumor therapeutic nanoagents has attracted tremendous recent attention. In this work, a new drug‐delivery vehicle based on human‐serum‐albumin (HSA)‐coated Prussian blue nanoparticles (PB NPs) is synthesized. It is demonstrated that doxorubicin (DOX)/HSA is successfully loaded after in situ polymerization of dopamine onto PB NPs, and the PB@PDA/DOX/HSA NPs are highly compatible and stable in various physiological solutions. The NPs possess strong near‐infrared (NIR) absorbance, and excellent capability and stability of photothermal conversion for highly efficient photothermal therapy applications. Furthermore, a bimodal on‐demand drug release sensitively triggered by pH or NIR irradiation has been realized, resulting in a significant chemotherapeutic effect due to the preferential uptake and internalization of the NPs by cancer cells. Importantly, the thermochemotherapy efficacy of the NPs has been examined by a cell viability assay, revealing a remarkably superior synergistic anticancer effect over either monotherapy. Such multifunctional drug‐delivery systems composed of approved materials may have promising biomedical applications for antitumor therapy.     

Elastic heterogeneity in metallic glasses

When a stress is applied on a metallic glass it deforms following Hook's law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about 3/4 in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.     

高功率脉冲非平衡磁控溅射放电特性和参数研究

用线圈电流控制非平衡磁场,用汤森放电击穿形成深度自触发放电,用磁阱捕获放电形成的二次电子和导致漂移电流,形成了高功率非平衡磁控溅射放电。采用偏压为-100V相对磁控靶放置的圆形平面电极收集饱和离子电流;在距离磁控靶14cm的位置由Langmuir探针测量浮置电位;示波器测量磁控靶的脉冲电压、电流、浮置电位和饱和离子电流信号。装置的放电脉冲功率达到0.9MW,脉冲频率最大值为40Hz左右,空间电荷限制条件是控制电子电流和离子电流的主要机制。     

热处理和紫外辐射对DNA影响的拉曼光谱研究

检测了鲕鱼精ＤＮＡ纤维和经过４０℃，９１℃，２００℃加热处理的拉曼光谱。研究结果表明，在熔融温度以下热处理对ＤＮＡ构象的影响是轻微的，在熔融温度以上则随温度的升高，对ＤＮＡ分子结构的影响有破坏也逐渐加剧，首先受影响的是腺嘌呤和脱氧核糖。     

Analysis and Verification on the Chain-like Model with Normal Distribution of Magnetorheological Elastomer

在磁流变弹性体链化模型的基础上,引入斜链夹角的正态分布,采用偶极子法从理论上分析了诸多因素对磁流变弹性体磁致剪切模量的影响,包括颗粒链的初始倾斜角、外加磁场强度、剪应变大小等,并进行了实验验证.     

TDI CCD像元响应不一致性校正算法

线阵TDI CCD遥感相机的不一致性校正对获取高质量的图像来说具有重要意义。主要对TDI CCD像元响应不一致性的校正算法及其硬件实现进行了深入的研究。对CCD的噪声特性进行了详细的分析,给出了像元响应不一致性(PRNU:Pixel-response non-uniformity)的退化模型及校正算法,并对其计算精度进行了分析,在硬件电路上对校正算法进行了验证,详细分析了影响校正效果的各种因素。实测结果表明,校正后图像的信噪比得到显著提高。