系列含钨原子簇化合物的红外光谱研究

本文报道了系列两核或四核的含钨原子簇化合物的红外光谱的研究结果。通过对这些化合物的光谱数据分析并结合它们的结构特征,归属了这些含有「Ｗ２Ｓ４」＾２＋和「Ｗ２ＭＭ’Ｓ４」＾４＋（Ｍ,Ｍ’＝Ｃｕ,Ａｇ）簇芯的原子簇化合物的主要振动谱峰,并讨论了结构的变化对光谱的影响。     

原子簇的结构和性质

原子簇是介于气体和固体之间的物质结构的新形态，具有与大块材料和单个原子均不相同的特征．本文从金属、惰性元素以及化合物分子几种不同物质构成的原子簇，来讨论奇偶性、幻数、同位素效应等奇异性质与其结构、尺寸和形成过程的内在联系，并指出原子簇存在的普遍性及其在基础学科和应用学科研究中的意义．     

原子吸收光谱法测定金属原子簇化合物中铬

报道了利用火焰原子吸收谱法测定金属原子簇化合物中铬,用钠离子消 除共存元素干扰,本法简便、快速,具有良好的准确度和精密度,相对标准偏差为0．60％－0．67％,回收率为100％－103％。     

金属原子簇化合物的拉曼光谱研究

金属原子簇化合物的拉曼光谱研究李淑玲（地矿部岩矿测试研究所北京１０００３７）任玲（北京理工大学化工与材料学院北京１０００８１）ＲａｍａｎＳｐｅｃｔｒｏｓｃｏｐｉｃＳｔｕｄｙｏｆＭｅｔａｌｃｌｕｓｔｅｒＣｏｎｐｏｕｎｄｓＬｉＳｈｕｌｉｎｇ（Ｉｎｓｔｉｔ...     

含铂卤素桥接混合价化合物的掺杂与电导

本文提出一个描述掺杂的含铂卤素桥接混合价化合物(HMPC)的模型Hamiltonian,利用Green函数方法计算了掺杂的HMPC的电导,详细讨论了掺杂的感应缺陷态,得到与实验符合得较好的结果。     

原子簇产生的统计规律与结构分析（Ⅱ）

通过对二元原子簇质谱的分析。发现以同种结构和机理生长的原子簇丰度符合对数正态分布，对于离子型二元原子簇，由统计规律描述的同一系列原子簇之间相差一个或数个符合宏观元素价态的化合物集团，并且随着原子簇的增大，只有保持宏观元素价态的原子簇系列才能免保留下来，而对于共价型二元原子簇，因为没有元素价态的限制，符合统计规律的一同系列原子簇一般由加减单一元素的的原子个数形成，由统计规律可以分析出可改变的元素原子     

准一维含铂混合价化合物中的激光诱导光吸收

本文研究准一维含铂卤素桥接混合价化合物(HMPC)中的激光诱导光吸收。在总结、分析实验事实的基础上,提出一个激光诱导光吸收机制,分别计算卤素(X)离子交替形变和描述极化子周围的X离子晶格形变这两种情况下的激光诱导光吸收谱,并与实验事实进行比较。 关键词：     

原子簇产生的统计规律与结构分析（Ⅲ）

多元原子簇的形成受统计规律所控制。由统计规律描述的原子簇通式为ＡＢｎ或ＡＢｎＣｍ，其中Ｂ，Ｃ为构成原子簇的可变的活性单元，它可能是单个原子，也可以是由几种元素组成的化合物集团，Ａ是同一系列原子簇的核心，由不同的Ａ加减Ｂ，Ｃ所生成的原子簇系列由不贩统计分布曲线来描述，从统计学观点来看，多元原子簇中的所胆ＡＢｎ和大部分（ＡＢｎ）Ｃｍ都可归为一类，具有与二元原子簇相似的规律，还有一些多元簇ＡＢｎＣｍ包含     

BeXY、MgXY（X、Y=F、Cl、Br）与ClF3和ClOF3形成复合物的理论研究

与卤素原子相比,超卤素表现出电负性更大、结构更丰富、性质更新颖等更加丰富的特征。本文以碱土金属Be、Mg的卤化物BeXY、MgXY（X、Y=F、Cl、Br）为母体,分别与卤素氟化物ClF3、ClOF3形成的复合物为研究对象,设计了12种配合物。采用密度泛函理论研究了这些化合物的结构、垂直电离能(VDE)、绝热电离能(ADE)等性质。研究发现,配合物中存在超卤素阴离子,所表现出来的性质远远优于常见的超卤素阴离子,因此,此类化合物具有很好的应用前景。     

DV-Xα方法与电子光谱解析

本文介绍了第一原理量子化学DV Xα方法在电子光谱的理论计算方面的应用。在三个例子中分别详细讨论了过渡金属原子簇的紫外 可见吸收谱V/UV、X 射线光电子能谱XPS、和XANES的计算 ,应用于MoS4原子簇结构、Cu2 O/Cu表面与 2 氨基嘧啶相互作用模型、和MoS2 导带底部结构分析。根据在不同光谱分析的特点 ,采用相应的计算方案。电子光谱的解析除了在解释光谱现象外 ,能够进一步帮助了解分子或原子簇的结构。     

Valence band formation in small silver clusters

UV photoemission spectra of valence electrons in small silver clusters have been compared with spectra from bulk silver samples using synchrotron radiation, 16 <hν< 27 eV. Spectra for single silver atoms supported on carbon are indicative of a completely filled 4d¹⁰ initial state configuration. With increased cluster size, both density of states and valence band modulations with respect to photon energy resemble the bulk metal more closely. Spectral modulation, characteristic of conservation of crystal momentum, appears to require a cluster consisting of ～150 atoms.     

A qualitative model for the growth mechanism of silver clusters in polymer solution

A simple and high-reproducible method for the synthesis of polymer-protected silver cluster of controlled size is described. UV-visible spectroscopy has been used for investigating the influence of the aging of the protective poly(vinylpyrrolidone) layer on the cluster growth rate at different reaction temperatures and poly(vinylpyrrolidone)/ethylene glycol weight ratios. The obtained results show that the aging time of the polymeric stabilizer solution plays a fundamental role in the reproducibility of the cluster growth process. A model for the metal cluster formation-grow process is also proposed. Received 18 July 2001 and Received in final form 3 October 2001     

Polyhedral silver clusters as single molecule ammonia sensor based on charge transfer-induced plasmon enhancement

The unique plasmon resonance characteristics of nanostructures based on metal clusters have always been the focus of various plasmon devices and different applications. In this work, the plasmon resonance phenomena of polyhedral silver clusters under the adsorption of NH₃, N₂, H₂, and CH₄ molecules are studied by using time-dependent density functional theory. Under the adsorption of NH₃, the tunneling current of silver clusters changes significantly due to the charge transfer from NH₃ to silver clusters. However, the effects of N₂, H₂, and CH₄ adsorption on the tunneling current of silver clusters are negligible. Our results indicate that these silver clusters exhibit excellent selectivities and sensitivities for NH₃ detection. These findings confirm that the silver cluster is a promising NH₃ sensor and provide a new method for designing high-performance sensors in the future.     

Calculations with the CNDO method on clusters of silver atoms

An attempt has been made to explore the applicability of the complete neglect of differential overlap (CNDO) method for investigating clusters of silver atoms. A new parametrization for silver has been obtained by comparing charge distributions, as well as local and total density of states, from CNDO calculations with those from the X_α scattered wave (X_αSW) method for an Ag₇ cluster which represents a fragment of the silver lattice. These parameters have then been used for making CNDO calculations on four further clusters of the same type, namely Ag₆, Ag₁₀, Ag₁₃ and Ag₁₉, and the results are compared with previous X_αSW calculations. These CNDO calculations give d-band widths in broad agreement with those from the X_αSW method. The most significant difference is that the CNDO method gives less localization on central atoms with high coordination numbers than is found from the X_αSW calculations. It is suggested that this apparent deficiency of the CNDO calculations may be less serious when the clusters are being used for modelling part of a solid metal rather than for specifically investigating the properties of small particles.     

Physical properties of silver-coated silica clusters: A computer experiment

The effect on the physical properties of a silica cluster after silver coating has been studied by the molecular dynamics method. It has been established that silver atoms make a sphere-like cluster shape, increase mechanical stability and give a stable positive value of the surface tension. They increase the number of electrons able to interact with the electromagnetic field, and, hence, enhance the efficiency of thermal radiation transfer by clusters.     

银团簇结构与特性的分子动力学研究

用分子动力学方法模拟了银团簇的结构与力能学。计算模拟中使用了一种基于第一性原理的原子间互作用多体势函数。通过分子动力学模拟确定了银徽团簇（原子个数3－13）的稳态结构;模拟了原子个数为13－141的银FCC晶体结构理想球形团簇的力能学,发现球形银簇形成三维紧密结构;计算了平均结合能,给出了结合能随团簇原子数N的变化图,发现随N增大团簇结合能逐渐接近块材的数值。     

Plasmon-enhanced fluorescence near metallic nanostructures: biochemical applications

Amplification of fluorescence is a nanoscale phenomenon which is particularly pronounced in close proximity to metal nanostructures. Due to its sharp distance dependence, it is ideally suited to monitor biorecognition reactions. Using this effect we have been able to demonstrate ultrasensitive bioassays. Two types of metal nanostructures have been employed, nanometric silver islands deposited over an ultrathin metal mirror and silver fractal structures. For the first type, metal mirrors (aluminum, gold, or silver protected with a thin silica layer) were coated with SIFs and an immunoassay (model assay for rabbit IgG or myoglobin immunoassay) was performed on this surface using fluorescently labeled antibodies. Our results show that SIFs alone (on a glass surface not coated with metal) enhance the immunoassay signal approximately 3 to 10-fold. Using a metal mirror instead of glass as support for SIFs leads to up to 50-fold signal enhancement. The second type of metal nanostructures, silver fractals, were produced by electrochemical reduction of silver nitrate deposited on sapphire covered with a thin conductive film of indium tin oxide. These structures were used as a substrate for a model rabbit IgG bioassay. The fluorescence resulting from the binding of antibody labeled with Rhodamine was highly nonuniform with distinctive hot spots. These highly fluorescent regions were correlated with areas of higher Ag thickness and coverage. Such high values of fluorescence amplification in both types of nanostructures have been interpreted by using time-resolved fluorescence data and by considering the radiative properties of plasmons in the environments which promote plasmon coupling. PACS 87.64.Ni; 81.07.-b; 87.14.-g     

Direct observation of the non-supported metal nanoparticle electron density of states by X-ray photoelectron spectroscopy

Synchrotron-based X-ray photoelectron spectroscopy on copper and silver cluster beams created by a magnetron-based gas-aggregation source has allowed mapping the electron density of states (DOS) of free metallic nanoparticles. The cluster DOS profiles obtained in the experiments strongly resemble the infinite solid DOS shapes, but the extracted cluster work-functions are lower than those for the bulk metal. The latter observation is explained by the initial negative charge on most of the clusters, created by the source.     

纳米结构表面形貌成型机理及其对石墨烯拉曼光谱的影响

通过真空热蒸镀和高温退火法制备的金属纳米复结构SERS基底因其具有良好的灵敏度,稳定性和均匀性而广泛应用于各种检测领域。石墨烯具有优良的光学特性,化学惰性以及荧光猝灭效应,自被发现以后一直是光学微纳器件中的一大热门材料。石墨烯还可以有效分离探针分子与基底,优化拉曼光谱质量,因此广泛应用于SERS研究领域。同时石墨烯可以有效隔绝金属纳米结构与空气的直接接触防止金属纳米结构被氧化而失效,也可以催化氧化银的脱氧反应提升SERS基底的稳定性。在石墨烯/金属纳米复合结构SERS基底在制备过程中,受到金属膜的种类、厚度参数、气体种类、退火时间、温度和气压等因素的影响,制备的金属纳米结构形貌存在很大差异。石墨烯的拉曼光谱会因为应力和掺杂导致其拉曼特征峰出现不同程度的增强,移动以及展宽。（1）采用真空热蒸镀法和高温退火法制备石墨烯/银纳米复合结构SERS基底,建立了金属纳米颗粒成型机理的模型,从孔洞形成、孔洞生长、金属纳米岛形成三个阶段分析了金属纳米粒子的成型过程,实验沉积5,10,15以及20 nm的银薄膜,退火后银纳米结构的覆盖率分别为~35.1%,~24.4%,~30%以及~96.0%,在沉积银薄膜样品上使用湿法转移石墨烯,退火处理后发现石墨烯阻止了银纳米岛的形成过程;（2）理论分析了银薄膜厚度、石墨烯覆盖对复合结构的几何形貌、拉曼增强特性的影响,石墨烯由于其具有较高的杨氏模量和表面张力,可以有效抑制退火过程中银薄膜向纳米粒子转变的过程,从而实现对复合结构表面形貌的调控;（3）实验研究了银纳米粒结构形貌对石墨烯拉曼光谱的影响,并理论分析了蒸镀不同银薄膜厚度的样品对石墨烯的拉曼光谱增强,移动以及展宽影响的具体原因。     

Structure, dynamic and energetic of mixed transition metal clusters

Classical molecular dynamics simulation (MD) with Sutton-Chen potential has been used to generate the minimum energy and to study the thermodynamic and dynamic properties of mixed transition metal cluster motifs of Ag _n Ni_(13?n) for n ?? 13. Literature results of thirteen particle clusters of neat silver and nickel atoms were first reproduced before the successive replacement of the silver atom by nickel. Calculation was repeated for both silver-centred and nickel-centred clusters. It was found that the nickel-centred clusters were more stable than the silver-centred clusters. Heat capacities and hence the melting points of silver and nickel-centred clusters were determined by using the Histogram method. Species-centric order parameters developed by Hewage and Amar were used to understand the dynamic behaviour in the transition of silver-centred clusters to more stable nickel-centred clusters. This species-centric order parameter calculation further confirmed the stability of nickel-centred clusters over those of silver-centred species.