Optical Properties of Noble Metal Clusters in Ultrathin Solid Films

We report on the optical properties (absorption, Raman response) of thin and ultrathin phthalocyanine and amorphous silicon films with incorporated noble metal clusters. The metal clusters cause the typical absorption features originating from their surface plasmon resonance. In ultrathin films, due to the spatially close interface, the plasmon absorption may be displaced from its resonance frequency in the bulk, and its average position may be controlled by the average thickness of the ultrathin optical film. For example, we observe a shift of the plasmon resonance of silver clusters in amorphous silicon films (on fused silica) from 440 nm to 740 nm, when the silicon thickness increases from zero up to 9 nm. The deposition experiments are accompanied by investigations of the film structure, particularly in order to estimate the silver cluster diameter, which is around 3 nm or less.     

Tuning Optical Properties of Encapsulated Clusters of Gold Nanoparticles through Stimuli‐Triggered Controlled Aggregation

Gold nanoparticles entrapped in the hollow polymer nanocapsules undergo pH‐mediated controlled aggregation. Encapsulated clusters of nanoparticles show absorbance at higher wavelengths compared with individual nanoparticles. The size of the aggregates is controlled by the number of nanoparticles entrapped in individual nanocapsules. Such controlled aggregation may permit small biocompatible nanoparticles exhibit desirable properties for biomedical applications that are typically characteristic of large nanoparticles.     

Electronic and Optical Properties of Hydrogenated Si Clusters

The geometric, electronic, and photoabsorption properties of some hydrogenated silicon clusters are investigated. The density functional theory with generalized gradient approximation fimctional is applied. Our study shows that the geometric structures of them relax with their increasing sizes. Synchronously, the polarizations of Si-H bonds become weak slowly but overlap populations increase. In Mulliken population analysis, we find a distinctive passivation effect （some electrons are transferred from outer Si atoms to the central Si with four-coordinate Si atoms）. Owing to the quantum confinement, the energy gap and the lowest excitation energy increase with the decreasing sizes. For nanometer scale cluster, the transition from the highest occupied molecular orbital to the lowest unoccupied molecular orbital state is usually prohibited.     

界面电子受体分子对硫化镉纳米微粒光学性质的影响

纳米微粒的光学性质是固体微结构、微器件研究中的重要方向。纳米微粒可用于光信息存储、转换及光开关等,影响其光学性质的因素有尺寸、结构、组成及其周围的化学环境等。在结构和成分不变时微粒的光学吸收带边(E_g)可由下式描述:     

Mixed Aggregates of 1-Methoxyallenyllithium with Lithium Chloride

A combined computational and ¹³C NMR study was used to investigate the formation of mixed aggregates of 1-methoxyallenyllithium and lithium chloride in tetrahydrofuran (THF) solution. The observed and calculated chemical shifts, as well as the calculated free energies of mixed aggregate formation (MP2/6-31+G(d)), are consistent with the formation of a mixed dimer as the major species in solution. Free energies of mixed dimer, trimer, and tetramer formation were calculated by using the B3LYP and MP2 methods and the 6-31+G(d) basis set. The two methods generated different predictions of which mixed aggregates will be formed, with B3LYP/6-31+G(d) favoring mixed trimers and tetramers in THF solution, and MP2/6-31+G(d) favoring mixed dimers. Formation of the sterically unhindered mixed dimers is also consistent with the enhanced reactivity of these compounds in the presence of lithium chloride. The spectra are also consistent with some residual 1-methoxyallenyllithium tetramer, as well as small amounts of higher mixed aggregates. Although neither computational method is perfect, for this particular system, the calculated free energies derived using the MP2 method are in better agreement with experimental data than those derived using the B3LYP method.     

The Optical Resolution of Chiral Tetrahedrone-type Clusters Contai- ning SCoFeM (M=Mo or W) Using High Performance Liquid Chromatography Chiral Stationary Phase

Optical resolution using high performance liquid chromatography chiral stationary phases has been widely used in many modern research fields such as asymmetric synthesis, asymmetric catalytic and separation of racemic pharmaceuticals. In the past years, various chiral stationary phases have been developed and have been commercially available1. Among them, polysaccharide based phases are the widely used CSPs. A wide variety of enantiomeric compounds including chiral aromatic alcohols, enant…     

尿素分子团簇线性和一阶非线性光学极化率的理论计算

检验分子晶体非线性光学极化率的可加性,对于确认有向气体模型(Oriented-Gas Model) 具有重要的科学意义,对探索新型实用的分子非线性光学材料也有实际的意义。本文对尿素晶体中分子簇非线性光学极化率的可加性做了详尽的理论研究。首次做到了尿素分子最近邻排布团簇的非线性光学极化率的从头算,从而扩展了前人的工作。研究结果有效地确认了有向气体模型。同时,我们还提出了壳层结构模型 (Shell-Structure Model),用以解决有向气体模型中的缺陷,可实现更为有效可靠地计算晶体宏观非线性光学系数。     

Assessing Solvation Effects on Chemical Reactions with Globally Optimized Solvent Clusters

We have examined the influence of water solvent on the Menshutkin reaction of methyl chloride with ammonia by performing static, quantum chemical calculations. We have employed large, explicit, and globally structure‐optimized water clusters around the reaction center, in a mixed explicit/implicit solvent model. This approach deliberately deviates from attempts to capture the most likely solvent‐molecule distribution around a reaction center. Instead, it explores extremes on the scale of rearrangement speed in terms of the surrounding solvent cluster, relative to the reaction progress itself. A comparison to traditional theoretical and experimental results enables us to quantify the energy penalty that is induced by the inability of the water cluster to instantaneously and completely follow the reaction progress. In addition, the influence of water clusters on the reaction energy profile can be much larger than merely changing it somewhat. Certain clusters can completely annihilate the sizeable activation barrier of 23.5 kcal mol^?1.     

Optical fibre SERS sensors

Surface-enhanced Raman scattering (SERS) has established itself as an important analytical technique. However, efforts to transfer the technology from the laboratory to the production line, clinic or field have been frustrated by the lack of robust affordable substrates and the complexity of interfacing between sample and spectrometer. Prompted by the success of optical fibre systems for implementing normal Raman scattering spectroscopy in remote locations and biomedical applications, attention has now shifted to the development of SERS-active optical fibres. Other workers have attempted to develop SERS probes with extended interaction lengths and both far-field and near-field SERS imaging techniques for high-resolution chemical mapping of surfaces. This review discusses the development of these technologies and presents the current state of the art. Although recent developments show great promise, some outstanding challenges and opportunities remain to be addressed.     

光通讯波段聚合物光波导材料的研究进展

光学聚合物由于其在光通讯领域的集成光电器件与光互连应用方面有经济和实用价值而备受关注。本文介绍了光通讯波段有机聚合物光波导材料的特点和研究进展。     

Reactions of Laser Ablation-magnesium Plasma with Methanol Clusters

IntroductionReactions of metal ions with neutral molecules orclusters produce a variety of metal complex ions andother new series of cluster ions including cations andanions.The laser ablation-molecular beam(LA-MB)method has marked its relevance in the st…     

Oxidation Effects on the Electronic Properties of Hydrogenated Silicon Clusters

The geometric and electronic properties of some hydrogenated silicon clusters in the presence of oxygen on the surface have been investigated.The density functional theory with generalized gradient approximation functional was applied in our calculations.By calculating the total energy,the double bond Si=O is shown to be more stable than the bridge bond Si-O-Si for large size oxidized clusters.The results of Mulliken population analysis indicate that a so-called passivation effect is enhanced by oxidization effects.From the energy band structures and density of states,we find that some localized states are induced by the p-orbital of O atom mainly and reduce the energy gaps substantially.     

Optical properties of binuclear zinc (II) macrocyclic complexes derived from 4-methyl-2,6-diformylphenol and 1,2-diaminobenzene

In this work, we present the synthesis and optical study of the binuclear zinc(II) macrocyclic complexes, derived from 4-methyl-2,6-diformylphenol and 1,2-diaminobenzene (H₂L). Two zinc macrocyclic complexes with different anions were prepared and characterized: [Zn₂LCl₂]·H₂O (1) and [Zn₂L](NO₃)₂ (2).     

Molybdenum-Tungsten Mixed-Metal Trinuclear Clusters with Two Capping Oxides and Six Bridging Acetates,and Other Mixed Molybdenum-Tungsten Clusters

Abstract

Mixed molybdenum-tungsten clusters of di-, tri-, tetra- and pentavalent metal ions are reviewed. Those having strong π-accepting and/or [sgrave]-donating ligands such as CO are not included. The complexes which have been prepared by the authors' group are described in more detail. These are trinuclear complexes ([Mo_nW_3-n(μ₃-O)₂(μ-CH₃COO)₆(H₂O)₃]²⁺) with the oxidation state four and dinuclear complex ([MoW(μ-O)₂-(O)₂(μ-N, N'-edta)]^2-) with the oxidation state five. Other complexes described are dinuclear complexes of divalent metal ions (‘Mo-W quadruple bond’) and of trivalent metal ions (“Mo-W triple bond”), and trinuclear complexes with i-propoxide ligands.     

光调控分子有序聚集体及其功能化研究进展

双亲分子在溶液中可以缔合形成胶束、囊泡、液晶、乳液等有序分子聚集体。在分子中引入功能性的基团,通过改变分子的结构、浓度或引入外部刺激,可以对有序分子聚集体的类型和性能进行调控。光作为一种绿色可控的清洁能源,是一种理想的外部刺激信号。在双亲分子中引入感光基团,可以通过光照调节有序聚集体的组装,并进一步实现功能性的调控。本文综述了近年来在光调控分子有序聚集体方面的研究及其在生物、传导、纳米材料制备中的应用。同时,对光调控的功能性有序分子聚集体未来的发展前景进行了展望。     

Lanthaballs: Chiral,Structurally Layered Polycarbonate Tridecanuclear Lanthanoid Clusters

New balls please! The viability of using carbonate as the primary anion in cluster formation is demonstrated in the synthesis of ‘lanthaballs’, spherical tridecanuclear lanthanoid complexes with a novel [Ln(CO₃)₆] moiety in a [Ln₁₃(CO₃)₁₄] core (see picture). The chirality of the lanthaballs is evidenced in the configuration of extended columns of π‐stacked phenanthroline ligands. The structural and magnetic properties of lanthaballs are investigated.