Preparation and electrochemical performance of bramble-like ZnO array as anode materials for lithium-ion batteries

A bramble-like ZnO array with a special three-dimensional (3D) nanostructure was successfully fabricated on Zn foil through a facile two-step hydrothermal process. A possible growth mechanism of the bramble-like ZnO array was proposed. In the first step of hydrothermal process, the crystal nucleus of Zn(OH) ₄ ^2? generated by the zinc atoms and OH^? ions fold together preferentially along the positive polar (0001) to form the needle-like ZnO array. In the second step of hydrothermal process, the crystal nuclei of Zn(OH) ₄ ^2? adjust their posture to keep their c-axes vertical to the perching sites due to the sufficient environmental force and further grow preferentially along the (0001) direction so as to form bramble-like ZnO array. The electrochemical properties of the needle- and bramble-like ZnO arrays as anode materials for lithium-ion batteries were investigated and compared. The results show that the bramble-like ZnO material exhibits much better lithium storage properties than the needle-like ZnO sample. Reasons for the enhanced electrochemical performance of the bramble-like ZnO material were investigated.     

单光子计数闪烁探测器灵敏度标定方法

根据NaI(Tl)闪烁探测器可用于单光子计数的特性,探索了一种测量放射源入射下闪烁探测器脉冲电荷谱来实现其绝对灵敏度标定的方法。实验对标定系统的电荷数字转换记录器进行了绝对标定,得到了用于ICF实验中重要诊断设备滤波-荧光谱仪的NaI(Tl)闪烁探测器的绝对灵敏度。灵敏度标定数据不确定度小于10%,较传统的放射源标定方法(15%)显著提高,同时标定能量范围扩大到100keV以上。最后,实验结果与Geant4模拟程序计算的结果进行了比对,符合得较好。     

Trapping of Organophosphorus Chemical Nerve Agents in Water with Amino Acid Functionalized Baskets

We prepared eleven amino‐acid functionalized baskets and used ¹H NMR spectroscopy to quantify their affinity for entrapping dimethyl methylphosphonate (DMMP, 118 ų) in aqueous phosphate buffer at pH=7.0±0.1; note that DMMP guest is akin in size to chemical nerve agent sarin (132 ų). The binding interaction (K_a) was found to vary with the size of substituent groups at the basket′s rim. In particular, the degree of branching at the first carbon of each substituent had the greatest effect on the host‐guest interaction, as described with the Verloop′s B1 steric parameter. The branching at the remote carbons, however, did not perturb the encapsulation, which is important for guiding the design of more effective hosts and catalysts in future.     

Chemiluminescent detection of cell apoptosis enzyme by gold nanoparticle-based resonance energy transfer assay

We report a new chemiluminescence resonance energy transfer (CRET) technique, using gold nanoparticles (AuNPs) as efficient energy acceptor, for homogeneous measurement of cell apoptosis enzyme with high sensitivity. In the design of the CRET system, we chose the highly sensitive chemiluminescence (CL) reaction between luminol and hydrogen peroxide catalysed by horseradish peroxidase (HRP) because the CL spectrum of luminol (λ _max 425 nm) partially overlaps the visible absorption bands of AuNPs. In this system, the peptide substrate (DEVD) of caspase 3 was linked to the AuNP surface by Au–S linkage. HRP was attached to the AuNP surface by means of a bridge formed by the streptavidin–biotin reaction. CRET occurred as a result of formation of AuNP–peptide–biotin–streptavidin–HRP complexes. The CL of luminol was significantly reduced, because of the quenching effect of AuNPs. The quenched CL was recovered after cleavage of DEVD by caspase 3, an enzyme involved in the apoptotic process. Experimental conditions were systematically investigated. Under the optimum conditions the increase of the CL signal was linearly dependent on caspase 3 concentration within the concentration range 25 pmol L^?1 to 800 pmol L^?1 and the detection limit of caspase 3 was as low as 20 pmol L^?1, one order of magnitude lower than for FRET sensors based on graphene oxides. Our method was successfully used to detect drug-induced apoptosis of cells. This approach is expected to be extended to other assays, i.e., using other enzymes, analytes, CL substances, and even other nanoparticles (e.g., quantum dots and graphene). Fig. a

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Ultrasensitive Plasmonic Response of Bimetallic Au/Pd Nanostructures to Hydrogen

Hydrogen detection is crucial for the safety of all hydrogen‐related applications. Compared to electrical hydrogen sensors, which usually suffer from possible electric sparks, optical hydrogen sensors offer advantages of remote and contact‐free readout and therefore the avoidance of spark generation. Herein, bimetallic Au/Pd nanostructure monolayers that exhibit ultrasensitive plasmonic response to hydrogen are reported. Bimetallic Au/Pd nanostructures with continuous and discontinuous Pd shells are prepared. The plasmonic response to hydrogen is monitored by measuring the extinction spectra of the ensemble Au/Pd nanostructures deposited on glass slides. Introduction of hydrogen induces red plasmon shifts, which become larger for the nanostructures with thicker Pd shells. For the nanostructures with continuous Pd shell, the plasmon shift can reach 56 nm at the hydrogen volume concentration below the explosion limit. The plasmon resonance wavelength displays an excellent linear dependence on the hydrogen volume concentration below 1%. The detection limit in the experiments reaches 0.2%. The nanostructures with discontinuous Pd shell show smaller plasmon shifts than those with continuous Pd shell. The extinction measurements on the ensemble nanostructures supported on transparent substrates and the unprecedentedly large plasmon shifts and sensitivity make the results very promising for the development of practical optical hydrogen sensors.     

Asymptotic stability of a composite wave of two viscous shock waves for the one-dimensional radiative Euler equations

This paper is devoted to the study of the wellposedness of the radiative Euler equations. By employing the anti-derivative method, we show the unique global-in-time existence and the asymptotic stability of the solutions of the radiative Euler equations for the composite wave of two viscous shock waves with small strength. This method developed here is also helpful to other related problems with similar analytical difficulties.     

Subsolidus phase diagram of the binary system (n-C n H2n+1NH3)2CoCl4

The perovskite-type layered compounds decylammonium tetrachlorocobaltate (n-C₁₀H₂₁NH₃)₂CoCl₄ and dodecylammonium tetrachlorocobaltate (n-C₁₂H₂₅NH₃)₂CoCl₄ exist the solid–solid phase transition in the temperatures range 330–380 K. These laminar materials contain bilayers sandwiched between metal halide layers. The experimental subsolidus binary phase diagram of (n-C₁₀H₂₁NH₃)₂CoCl₄–(n-C₁₂H₂₅NH₃)₂CoCl₄ has been established over the whole composition range by differential thermal analysis and X-ray diffraction. In the phase diagram, one intermediate compound (n-C₁₀H₂₁NH₃) (n-C₁₂H₂₅NH₃)CoCl₄ at $ W_{{{\text{C}}_{ 1 0} {\text{Co}}}} \% = 50. 9 2 $ and two eutectoid invariants points at $ W_{{{\text{C}}_{ 10} {\text{Co}}}} \% = 2 9. 8 3 $ and $ W_{{{\text{C}}_{ 10} {\text{Co}}}} \% = 7 7. 9 8 $ were observed, two eutectoids temperatures are about 343 ± 1 and 340 ± 1 K. There are three noticeable solid solution ranges (α, β, γ) at the left and right boundary and middle of the phase diagram.     

数字视频压缩编码技术标准现状与展望

信息技术和计算机互联网技术的飞速发展改变了人们的生活方式,以视频为核心的多媒体信息已经成为人们获取信息的主要来源,随着视频存储与传输的广泛应用,高效视频编码技术研究已经成为多媒体技术的研究热点。系统讨论了当前流行的视频编码技术标准及框架与采用的关键技术、标准的效率与复杂度的关系,并重点分析了未来视频编码技术的发展趋势。     

An Adjustable pH‐Responsive Drug Delivery System Based on Self‐Assembly Polypeptide‐Modified Mesoporous Silica

In this study, an adjustable pH‐responsive drug delivery system using mesoporous silica nanoparticles (MSNs) as the host materials and the modified polypeptides as the nanovalves is reported. Since the polypeptide can self‐assemble via electrostatic interaction at pH 7.4 and be disassembled by pH changes, the modified poly(l ‐lysine) and poly(l ‐glutamate) are utilized for pore blocking and opening in the study. Poly(l ‐lysine)‐MSN (PLL‐MSN) and poly(l ‐glutamate)‐MSN (PLG‐MSN) are synthesized via the ring opening polymerization of N‐carboxyanhydrides onto the surface of mesoporous silica nanoparticles. The successful modification of the polypeptide on MSN is proved by Zeta potential change, X‐ray photoelectron spectroscopy (XPS), solid state NMR, and MALDI‐TOF MS. In vitro simulated dye release studies show that PLL‐MSN and PLG‐MSN can successfully load the dye molecules. The release study shows that the controlled release can be constructed at different pH by adjusting the ratio of PLL‐MSN to PLG‐MSN. Cellular uptake study indicates that the drug is detected in both cytoplasm and nucleus, especially in the nucleus. In vitro cytotoxicity assay indicates that DOX loaded mixture nanoparticles (ratio of PLL‐MSN to PLG‐MSN is 1:1) can be triggered for drug release in HeLa cells, resulting in 88% of cell killing.     

Crystalline Diradical Dianions of Pyrene-Fused Azaacenes

Although diradicals and azaacenes have been greatly attractive in fundamental chemistry and functional materials, the isolable diradical dianions of azaacenes are still unknown. Herein, we describe the first isolation of pyrene-fused azaacene diradical dianion salts [(18-c-6)K(THF)₂]⁺[(18-c-6)K]⁺⋅ 1 ^2−.. and [(18-c-6)K(THF)]²⁺⋅ 2 ^2−.. by reduction of the neutral pyrene-fused azaacene derivatives 1 and 2 with excess potassium graphite in THF in the presence of 18-crown-6. Their electronic structures were investigated by various experiments, in conjunction with theoretical calculations. It was found that both dianions are open-shell singlets in the ground state and their triplet states are thermally readily accessible owing to the small singlet–triplet energy gap. This work provides the first examples of crystalline diradical dianions of azaacenes with considerable diradical character.