TiO<Subscript>2</Subscript> nanotube arrays: a study on the surface electrochemical reactions during the photoelectrochemical process

The surface electrochemical reactions of TiO₂ nanotube arrays (NTAs) corresponding to different active species of TiO₂ NTAs (·OH, h⁺, and ·O₂ ^?) play key roles during the photoelectrochemical process. Effect of the active species and surface electrochemical reactions are studied by adding capture agents of isopropyl alcohol (IPA) for ·OH, ammonium oxalate ((NH₄)₂C₂O₂) for h⁺, and benzoquinone (BQ) for ·O₂ ^? radicals. The changes of photocurrent with addition of capture agents confirm the existence of ·OH, h⁺, and ·O₂ ^? during photoelectrochemical process. IPA and (NH₄)₂C₂O₂ additions are found to enhance the photocurrent by accelerating the consumption velocity of h⁺ indirectly and directly and restricting the chargers recombination. BQ can decrease the photocurrent stepwise to 0 due to the indirect consumption of e^? on surface of TiO₂ NTAs. The consumption of h⁺ by forming ·OH is 38% that of the whole consumption of h⁺. The ratio of chargers recombination is higher than 80.8% that of the whole photogenerated chargers.     

Investigation of 3D Dirac semimetal supported terahertz dielectric-loaded plasmonic waveguides

The tunable propagation properties of 3D Dirac semimetal (DSM)-supported dielectric-loaded surface plasmons structures have been investigated in the THz regime, including the influences of the Fermi level of 3D DSM layer, the fiber shape and operation frequencies. The results indicate that the shape of dielectric fiber affects the hybrid mode significantly, on the condition that if a_x (the semi-minor axis length of the dielectric semi-ellipse) is relatively small, the fiber shows good mode confinement and low loss simultaneously, and the figure of merit reaches more than 200. The propagation property can be manipulated in a wide range by changing the Fermi level of 3D DSM, e.g. if the Fermi level varies in the range of 0.05 eV–0.15 eV, the propagation length changes in the range of 9.073×10³–2.715×10⁴ μm, and the corresponding modulation depth is 66.5%. These results are very helpful to understand the tunable mechanisms of the 3D DSM plasmonic devices, such as switchers, modulators, and sensors.     

基于委托—代理理论的自然灾害保险模型

灾害保险是筹措防灾救灾资金的重要手段之一，文章运用博弈论中的委托—代理理论建立自然灾害的保险模型，对有关自然灾害的最优保险费率的确定及其特征进行了研究，为开展自然灾害的保险业务提供理论依据     

多层膜结构对硬度实验影响的数值分析

为了研究多层膜结构对纳米微硬度实验的影响,用FEPG对纳米微硬度实验中压头的压入过程进行数值模拟,分析了由TiN,Al,Ti组成的多层膜中软膜材料不同、软膜与硬膜厚度比不同以及多层膜层数不同对膜层体系产生的影响,得出梯度变化的膜层结构能够提高膜层的整体性能,为纳米微硬度实验提供了一定的参考依据．     

Synthesis and magnetic properties of Ni-doped zinc oxide powders

Polycrystalline Zn_1−xNi_xO diluted magnetic semiconductors have been successfully synthesized by an auto-combustion method. X-ray diffraction measurements indicated that the 5 at% Ni-doped ZnO had the pure wurtzite structure. Refinements of cell parameters from powder diffraction data revealed that the cell parameters of Zn_0.95Ni_0.05O were a little bit larger than ZnO. Transmission electron microscopy observation showed that the as-synthesized powders were of the size ∼60 nm. Magnetic investigations showed that the nanocystalline Zn_0.95Ni_0.05O possessed room temperature ferromagnetism with the saturation magnetic moment of 0.1 emu/g (0.29 μ_B/Ni²⁺).     

Modification of polypyrrole nanowires array with platinum nanoparticles and glucose oxidase for fabrication of a novel glucose biosensor

A novel glucose biosensor, based on the modification of well-aligned polypyrrole nanowires array (PPyNWA) with Pt nanoparticles (PtNPs) and subsequent surface adsorption of glucose oxidase (GOx), is described. The distinct differences in the electrochemical properties of PPyNWA–GOx, PPyNWA–PtNPs, and PPyNWA–PtNPs–GOx electrodes were revealed by cyclic voltammetry. In particular, the results obtained for PPyNWA–PtNPs–GOx biosensor showed evidence of direct electron transfer due mainly to modification with PtNPs. Optimum fabrication of the PPyNWA–PtNPs–GOx biosensor for both potentiometric and amperometric detection of glucose were achieved with 0.2 M pyrrole, applied current density of 0.1 mA cm⁻², polymerization time of 600 s, cyclic deposition of PtNPs from −200 mV to 200 mV, scan rate of 50 mV s⁻¹, and 20 cycles. A sensitivity of 40.5 mV/decade and a linear range of 10 μM to 1000 μM (R² = 0.9936) were achieved for potentiometric detection, while for amperometric detection a sensitivity of 34.7 μA cm⁻² mM⁻¹ at an applied potential of 700 mV and a linear range of 0.1–9 mM (R² = 0.9977) were achieved. In terms of achievable detection limit, potentiometric detection achieved 5.6 μM of glucose, while amperometric detection achieved 27.7 μM.     

A fast multiscale Kantorovich method for weakly singular integral equations

In this paper, we use the idea of Kantorovich regularization to develop the fast multiscale Kantorovich method and the fast iterated multiscale Kantorovich method. For some kinds of weakly singular integral equations with nonsmooth inhomogeneous terms, we show that our two proposed methods can still obtain the optimal order of convergence and superconvergence order, respectively. Numerical examples are given to demonstrate the efficiency of the methods.     

Ultrafast dynamics of thermionic emission on Au film under femtosecond laser excitation

A high-fidelity numerical model for investigations of the ultrafast heating is highly desirable for simulating the pulsed laser damage and the ultrafast electron emission characteristics. However, realization of accurate predictions of thermal dynamics and thermionic electron emission remains challenging due to the high non-equilibrium state, in which the equilibrium heating parameters are invalid. Here, we report an axisymmetric two-dimensional (2-D) high-fidelity numerical model for predictions of the thermionic emission with respect to the temperature-dependent dynamics parameters. The spatio-temporal temperature evolution dynamics and the thermionic emission rate characteristics on Au film target are demonstrated, whose credibility is approved by the Au film ablation threshold experiments.     

Clean and Green Procedure for the Synthesis of Biodiesel from the Esterification of Free Fatty Acids and Alcohol Catalyzed by 6-<Emphasis Type="Italic">O</Emphasis>-(sulfobutyl)-β-cyclodextrin

The catalyst of 6-O-(sulfobutyl)-β-cyclodextrin (SB-CD) is renewable, non-toxic, environmentally benign and biocompatible, which could be used as efficient and recyclable catalyst for the synthesis of biodiesel from free long-chain fatty acids with low-chain alcohols as substrates. The reaction was accomplished at 60°C for 1.5 h, while the products were separated from the catalyst system by liquid/liquid at room temperature with good conversion of 91–98%. The catalyst can be reused for 10 times. The novel and clean procedure offers advantages including short reaction time, good conversion, operational simplicity, and environmentally benign characteristics.     

C_(60)与含受电子生色基团聚合物的电荷转移现象

Ｃ６０与含受电子生色基团聚合物的电荷转移现象邱健姚光庆周锡煌李福绵（北京大学化学与分子工程学院北京１００８７１）关键词Ｃ６０，聚［Ｎ （４ 氰基苯基）丙烯酰胺］，电荷转移现象，荧光光谱随着对球壳烯性质的深入认识，球壳烯与电子给、受体的电荷转移现象日...