Buckled nano rod – a two state system: quantum effects on its dynamics

We consider a suspended elastic rod under longitudinal compression. The compression can be used to adjust potential energy for transverse displacements from the harmonic to the double well regime. The two minima in potential energy curve describe two possible buckled states. Using transition state theory (TST) we have calculated the rate of conversion from one state to other. If the strain ? = 4? _c the simple TST rate diverges. We suggest a method to correct this divergence for quantum calculations. We also find that zero point energy contributions can be quite large so that single mode calculations can lead to large errors in the rate.     

表面能对纳米颗粒的晶格收缩和固有频率的影响

由于纳米颗粒具有很大的比表面积，因此，表面能对它的力学性能有着不可忽略的影响．本文给出了由表面能所导致的纳米颗粒晶格收缩效应的解析结果，与试验观察定量上相当一致；计算了表面能对纳米颗粒固有频率的影响，预测了由于表面能的影响，纳米颗粒出现的“振动软化”现象．     

Nuclear energy conversion with stacks of graphene nanocapacitors

The efficiency of conventional techniques used to harvest energy in nuclear reactors lies around 35%. This limit exists, because the nuclear energy is converted to electrical energy via heat engines. We study an alternative approach where the kinetic energy of nuclear reaction products is directly converted into electric energy in a stack of charged capacitors with a gap size of 500 nm and graphene electrodes. Graphene is expected to be chemically and mechanically stable in high‐radiation environments, because its tensile strength of 130 GPa is very large, about 100 times larger than most metals. The dielectric strength of such nanocapacitors exceeds 1 GV/m, because avalanching is suppressed at small gap sizes. In a 1 GV/m electric field charged nuclear reaction products, such as 5.6 MeV alpha particles, come to rest in of a stack with 5000 nanocapacitors. We show that during the deceleration process more than 90% of kinetic energy of charged nuclear reaction products is converted to electric energy and stored as electric energy in the stack. Each stack is 2.5‐mm thick and produces a high‐voltage DC current. A device with a 1‐Ci²⁴¹Am source is expected to generate 22 mW of electric power.     

Influence of sintering temperature and pH on the phase transformation,particle size and anti-reflective properties of RHA nano silica powders

Nano silica powders were synthesized from rice husk ash, the most silica-rich raw material, using alkaline extraction followed by acid precipitation. The phase transformation during sintering, the influence of sintering temperature and pH on the particle size and anti-reflective properties of nano silica were investigated. The results showed that the amorphous SiO₂ sintered at 600°C were transformed to a cristobalite structures completely during the sintering process at 800°C and 1100°C. With the increasing sintering temperature and pH, the particle size distributions (d₅₀) were increased respectively in the range of 62–84, 192–240, and 283–329?nm at sintering temperatures of 600°C, 800°C, and 1100°C. When the sintering temperatures were increased at 1100°C, 98.15% and 96.84% of transmittances were obtained respectively at the highest and lowest points of the anti-reflection band and could be used for anti-reflective applications.     

X‐ray diffraction analysis of powder and thin film of (Gd1‐x Yx)2O3 prepared by sol‐gel process

The mixed oxide (Gd_1‐xY_x)₂O₃ (0.0 ≤ x ≤ 1.0) were synthesized, as powder and thin film, by a sol‐gel process. X‐ray diffraction data were collected and crystal structure and microstructure analysis were performed using Rietveld refinement method. All samples were found to have the same crystal system and formed solid solutions over the whole range of x. The cationic distribution, Gd³⁺ and Y³⁺, over the two non‐equivalent sites 8b and 24d of the space group Ia3 is found to be random for all values of (x). The lattice parameter is found to vary linearly with the composition (x). Replacing Gd³⁺ and Y³⁺ by each other introduces a systemic decrease in the x‐coordinate of cation position (24d) and slight changes in the oxygen coordinates. Crystallite size and microstrain analysis is performed along different crystallographic directions and anisotropic changes are found with the composition parameter (x). The average crystallite size ranges from 75 to 149 nm and the r.m.s strain from 0.027 to 0.068 x10^‐2. Textured Gd_1.841Y_0.159O₃ (400) buffer layers, with a high degree of alignment in both out‐plane and in‐plan, are successfully grown on cube textured Ni (001) tape substrates by sol–gel dip coating process. The resulting buffer layers are crack‐free, pinhole‐free, dense and smooth. YbBa₂Cu₃O_7‐x (YbBCO) thin film could be (00l) epitaxially grown on the obtained buffer layer using sol–gel dipping technique. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Metal‐nanoparticle plasmonics

The rapid emergence of nanoplasmonics as a novel technology has been driven by recent progress in the fabrication, characterization, and understanding of metal‐nanoparticle systems. In this review, we highlight some of the key advances in each of these areas. We emphasize the basic physical understanding and experimental techniques that will enable a new generation of applications in nano‐optics.     

Synthesis of 4‐((2‐hydroxynaphthalen‐1‐yl)(aryl)methyl)‐5‐methyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐ones using nano‐Zn‐[2‐boromophenyl‐salicylaldimine‐methylpyranopyrazole]Cl2 nanoparticles

Nano‐Zn‐[2‐boromophenyl‐salicylaldimine‐methylpyranopyrazole]Cl₂ (nano‐[Zn‐2BSMP]Cl₂) as a nanoparticle Schiff base complex and a catalyst was introduced for the solvent‐free synthesis of 4‐((2‐hydroxynaphthalen‐1‐yl)(aryl)methyl)‐5‐methyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐ones by the multicomponent condensation reaction of various aromatic aldehydes, β‐naphthol, ethyl acetoacetate, and phenyl hydrazine at room temperature.     

基于水分散纳米无定形水杨酸甲酯铽配合物的三价铬离子高灵敏荧光传感器

为扩大稀土荧光配合物的应用范围,满足水溶液中微量铬的高灵敏高选择性探测要求,制备了一种基于水分散纳米无定形水杨酸甲酯铽配合物(A-MS-Tb)的高灵敏三价铬离子荧光传感器。结果表明:在水溶液中直接反应合成的配合物A-MS-Tb为无定形的纳米沉淀,其粒子尺度在50～100 nm之间,具有与报道的配合物晶体类似的组成。该配合物在494、549、591和625 nm处呈现出强的荧光发射,归属于铽离子的5D4→7FJ(J=6,5,4,3)能级跃迁。A-MS-Tb与晶体配合物的显著差别在于其在水中的悬浮稳定性和荧光稳定性更好,这对于其作为荧光材料和离子传感器非常重要。尤其突出的是,当将三价铬离子加入到它的水悬浮溶液中后,会减弱配体与铽离子之间的配位作用,导致其绿色荧光被淬灭。据此,构建了一种高灵敏测定溶液中铬离子浓度的荧光探针,并对其分析的选择性、灵敏度和抗干扰能力进行了评价。     

Organic polymer‐based monolithic capillary columns and their applications in food analysis

In recent years, the use of organic polymer monolithic capillary columns in separation science has gained popularity due to the fact that they are easy to fabricate and do not require retaining frits. These materials have been applied in different fields including foods, proteomics, and pharmaceuticals. The interest in food analysis still needs to develop in order to increase the sensitivity towards micro/nano‐scale food applications for food samples of < 5 μg (e.g., foodomics). In this regard, polymer monolithic capillary columns offer great separation capability in the food analytical separation science. We review the most important applications in food analysis using polymer monolithic capillary columns. In addition, several examples of the use of capillary separation methods combined with mass spectrometry detection in food analysis are summarized.     

Nano‐MoO3 for highly selective enrichment of polycyclic aromatic hydrocarbons in in‐tube solid‐phase microextraction

Nano‐molybdenum trioxide was prepared from nano‐molybdenum disulfide by simple firing in muffle furnace. Nano‐molybdenum trioxide was used as the extraction coating on the stainless steel wire. Four wires were filled in a polyetheretherketone tube to get an extraction tube. The tube was connected to the six‐port valve of a high performance liquid chromatograph, and the online analysis system was constructed. Extraction selectivity of the tube for different types of compounds, including polycyclic aromatic hydrocarbons, plasticizers, estrogens, anilines and neonicotinoids, was studied. Good enrichment ability for polycyclic aromatic hydrocarbons, but the extraction efficiency of others was not satisfactory. Using eight polycyclic aromatic hydrocarbons as the targets, an analytical method was established after optimizing main factors such as sampling volume, sampling rate, methanol content, and desorption time. The established method exhibited wide linear range to 0.016–20.00 μg/L and low limits of detection to 0.005 μg/L, and the enrichment factors can be up to 2443. The method was applied to the detection of trace polycyclic aromatic hydrocarbons in tap water and river water, and a good recovery was obtained. The tube showed good durability and chemical stability, and it still remained good extraction effect after more than 140 run.