Solvothermal Preparation and Effects of Mixed Solvent on the Properties of Copper Indium Diselenide Nanoalloys

We have developed a simple solvothermal method by using solvent mixtures of ethylenediamine with ethanol and deionized water to produce the CuInSe₂ nanoalloys. The phase structure, morphology, elemental composition and optical band gap (E_g) of synthesized the CuInSe₂ nanoalloys were characterized by Raman spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS) and zeta potential particle sizer measurements. The factors affecting product purity in the mixed solvent are also discussed. The results showed that CuInSe₂ nanoalloys with a chalcopyrite tetragonal structure were produced by adjusting the ratio of ethylenediamine to ethanol (1:2.33 by volume) and their corresponding energy band gap was found to be 1.27 eV. In addition, we prepared and coated the CuInSe₂ ink on the Mo substrate by the doctor blade method to produce a compact thin film. The crystallinity and the morphology of these polycrystalline CuInSe₂ films were characterized.     

Substrate‐Independent Magnetic Bistability in Monolayers of the Single‐Molecule Magnet Dy2ScN@C80 on Metals and Insulators

Magnetic hysteresis is demonstrated for monolayers of the single‐molecule magnet (SMM) Dy₂ScN@C₈₀ deposited on Au(111), Ag(100), and MgO|Ag(100) surfaces by vacuum sublimation. The topography and electronic structure of Dy₂ScN@C₈₀ adsorbed on Au(111) were studied by STM. X‐ray magnetic CD studies show that the Dy₂ScN@C₈₀ monolayers exhibit similarly broad magnetic hysteresis independent on the substrate used, but the orientation of the Dy₂ScN cluster depends strongly on the surface. DFT calculations show that the extent of the electronic interaction of the fullerene molecules with the surface is increasing dramatically from MgO to Au(111) and Ag(100). However, the charge redistribution at the fullerene‐surface interface is fully absorbed by the carbon cage, leaving the state of the endohedral cluster intact. This Faraday cage effect of the fullerene preserves the magnetic bistability of fullerene‐SMMs on conducting substrates and facilitates their application in molecular spintronics.     

One‐Pot Synthesis of Highly Substituted Polyheteroaromatic Compounds by Rhodium(III)‐Catalyzed Multiple CH Activation and Annulation

A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple C? H bond cleavage and C? C and C? N bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho C? H activation, alkyne insertion, and reductive elimination, is proposed for this transformation.     

The First Heteropentanuclear Extended Metal‐Atom Chain: [Ni+Ru25+Ni2+Ni2+(tripyridyldiamido)4(NCS)2]

This study develops the first heteropentametal extended metal atom chain (EMAC) in which a string of nickel cores is incorporated with a diruthenium unit to tune the molecular properties. Spectroscopic, crystallographic, and magnetic characterizations show the formation of a fully delocalized Ru₂⁵⁺ unit. This [Ru₂]‐containing EMAC exhibits single‐molecule conductance four‐fold superior to that of the pentanickel complex and results in features of negative differential resistance (NDR), which are unobserved in analogues of pentanickel and pentaruthenium EMACs. A plausible mechanism for the NDR behavior is proposed for this diruthenium‐modulated EMAC.     

Regiospecific Coordination of Re3 Clusters with the Sumanene‐Type Hexagons on Endohedral Metallofullerenes and Higher Fullerenes That Provides an Efficient Separation Method

The reactions of [(μ‐H)₃Re₃(CO)₁₁(NCMe)] with Sc₂@C₈₂‐C_3v(8), Sc₂C₂@C₈₀‐C_2v(5), Sc₂O@C₈₂‐C_s(6), C₈₆‐C₂(17), and C₈₆‐C_s(16) have been carried out to produce face‐capping cluster complexes. The Re₃ triangles are found to bind to the sumanene‐type hexagons on the fullerene surface regiospecifically. In contrast, Sc₃N@C₇₈‐D_3h(5) and Sc₃N@C₈₀‐I_h show no reactivity toward [(μ‐H)₃Re₃(CO)₁₁(NCMe)], probably due to electronic and steric factors. These complexes can be easily purified by using HPLC. Carbonylation of each complex releases the corresponding higher fullerene or endohedral metallofullerene in pure form. Remarkably, the C₈₆‐C₂(17) and C₈₆‐C_s(16) isomers were successively separated through Re₃ cluster complexation/decomplexation. This unique bonding feature may provide an attractive general strategy to purify as yet unresolved fullerene mixtures.     

中华白海豚和东亚窄脊江豚回声定位信号分析与比较

为了增进珍稀齿鲸物种的了解和保护,对中华白海豚(Sousa chinensis)和东亚窄脊江豚(Neophocaena asiaeorientalis sunmeri)的回声定位信号特性进行了分析和比较。通过船只观测与声学监听的方式对厦门海域中华白海豚和东亚窄脊江豚的回声定位信号进行了调查,并对其声学参数进行了统计和对比。结果表明:中华白海豚回声定位信号具有持续时间短、高频、宽频带的特征;相较而言,东亚窄脊江豚则呈现时长较长、高频、窄频带的特点;声学参数统计上,两者在持续时间、中心频率、-10 dB带宽等指标上具有明显的差异性。     

一种宽吻海豚通讯信号自动分类的方法

针对宽吻海豚通讯信号自动分类提出了一种基于句法模式识别的方法。该方法首先提取海豚通讯信号基频随时间变化的轨迹曲线,然后提取基频变化的基元序列。根据海豚通讯信号分类的标准,归纳出产生各类海豚通讯信号基频基元序列的文法。对未知类别的海豚通讯信号,提取其基频变化的基元序列,根据各类模式的文法对基元序列进行分类,进而实现海豚通讯信号的自动分类。实验结果显示本文方法的分类准确率达到了95%。本文方法预期为海豚生物学行为的声学研究提供一定的技术支持。     

Conservative flux recovery from the Q1 conforming finite element method on quadrilateral grids

Compared with standard Galerkin finite element methods, mixed methods for second‐order elliptic problems give readily available flux approximation, but in general at the expense of having to deal with a more complicated discrete system. This is especially true when conforming elements are involved. Hence it is advantageous to consider a direct method when finding fluxes is just a small part of the overall modeling processes. The purpose of this article is to introduce a direct method combining the standard Galerkin Q1 conforming method with a cheap local flux recovery formula. The approximate flux resides in the lowest order Raviart‐Thomas space and retains local conservation property at the cluster level. A cluster is made up of at most four quadrilaterals. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 20: 104–127, 2004     

Three-body Problem in Quantum Mechanics

No Abstract. . Lecture held in the Seminario Matematico e Fisico on May 26, 2004 Received: August 2004