Adsorption of Propene on Neutral Gold Clusters in the Gas Phase

The adsorption of propene on neutral gold clusters is investigated in a collision cell under a few collision conditions. The adsorption reaction is studied by pressure‐dependent kinetic measurements and delayed unimolecular dissociation of the excited Au_n?propene complexes. The cluster size (n=9–25) and temperature (T=90–300 K) dependence of the propene adsorption is analyzed. Strong size dependences of the absorption reaction are observed; a larger propene adsorption probability was found for gold clusters composed of an even number of atoms. Propene binding energies are estimated by comparison of the temperature‐dependent unimolecular dissociation rates with rates obtained by using statistical RRKM modeling. The Au_n–propene binding energies decrease non‐monotonously with cluster size and are in the range of 1.2–0.85 eV for n=9–25. Finally, the bonding of C₃H₆ on Au_n is qualitatively described and similarities with the absorption of CO molecules on gold clusters are discussed.     

Observable Structures of Small Neutral and Anionic Gold Clusters

Since gold clusters have mostly been studied theoretically by using DFT calculations, more accurate studies are of importance. Thus, small neutral and anionic gold clusters (Au_n and Au_n^?, n=4–7) were investigated by means of coupled cluster with singles, doubles, and perturbative triple excitations [CCSD(T)] calculations with large basis sets, and some differences between DFT and CCSD(T) results are discussed. Interesting isomeric structures that have dangling atoms were obtained. Structures having dangling atoms appear to be stable up to n=4 for neutral gold clusters and up to n=7 for anionic clusters. The relative stabilities and electronic properties of some isomers and major structures are discussed on the basis of the CCSD(T) calculations. This accurate structure prediction of small gold clusters corresponding to experimental photoelectron spectral peaks is valuable in the field of atom‐scale materials science including nanocatalysts.     

Argon Adsorption on Cationic Gold Clusters Aun+ (n ≤ 20)

The interaction of Au_n⁺ (n ≤ 20) clusters with Ar is investigated by combining mass spectrometric experiments and density functional theory calculations. We show that the inert Ar atom forms relatively strong bonds with Au_n⁺. The strength of the bond strongly varies with the cluster size and is governed by a fine interplay between geometry and electronic structure. The chemical bond between Au_n⁺ and Ar involves electron transfer from Ar to Au, and a stronger interaction is found when the Au adsorption site has a higher positive partial charge, which depends on the cluster geometry. Au₁₅⁺ is a peculiar cluster size, which stands out for its much stronger interaction with Ar than its neighbors, signaled by a higher abundance in mass spectra and a larger Ar adsorption energy. This is shown to be a consequence of a low-coordinated Au adsorption site in Au₁₅⁺, which possesses a large positive partial charge.     

Superoxide Formation on Isolated Cationic Gold Clusters

Gold nanoparticles are known to be highly versatile oxidation catalysts utilizing molecular oxygen as a feedstock, but the mechanism and species responsible for activating oxygen remain unclear. The reaction between unsupported cationic gold clusters and molecular oxygen has been investigated. The resulting complexes were characterized in the gas phase using IR spectroscopy. A strong red‐shift in the observed ν(O‐O) stretching frequency indicates the formation of superoxo (O₂^?) moieties. These moieties are seen to form spontaneously in systems, which upon electron transfer attain a closed shell within the spherical jellium model (Au₁₀⁺ and Au₂₂⁺), whereas an oxygen induced self‐promotion in the activation is observed for other systems (Au₄⁺, Au₁₂⁺, Au₂₁⁺).     

金纳米团簇功能化及其在生物医学中的应用

对单分子层保护的金纳米团簇(Au-MPCs)进行化学修饰,可制成多元单层修饰的金纳米团簇（Au-MMPCs）。常用的修饰方法为配体交换法,这种方法用带有生物活性基团的巯基化合物或二硫化合物取代Au-MPCs表面的配体分子,形成多元单层修饰的金纳米团簇。巯基化合物或二硫化合物中的生物活性基团可使所制备Au-MMPCs与蛋白质、核酸或细胞膜等作用,使Au-MMPCs具有相应的生物活性,从而能广泛应用于细胞转染、药物传输、酶活性调控等生物医学领域。本文介绍了用Brust-Schiffrin法制备Au-MMPCs的机理及影响因素,基于Au-MMPCs的方法及相关机理,综述了Au-MMPCs在生物医学中的应用。     

Density Functional Theory Study of HCN Adsorption on Small Gold Clusters

A theoretical study was carried out on the adsorption of hydrocyanic acid on small Aun （n ≤ 7） clusters using density functional methods. For HCN adsorption on gold clusters, no dependence was found with respect to the even-odd alternation in relation to the number of gold atoms in the cluster. The HCN molecule is adsorbed at simple adsorption sites （1-fold coordination）, perpendicular to the adsorption site. The largest adsorption energy is only about 74.61 kJ·mol^-1, which indicates that the HCN molecule does not decompose and the C-N bond retains triple bond, and that the C-H and C-N stretching frequencies are only weakly perturbed. The adsorbed C-N and C-H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.     

Fluorescent Gold Clusters as Logic Gates for the Detection of Different Metal Ions

Metal cations can be selectively detected by restoring and quenching the fluorescent intensity of an “ON–OFF” gold nanocluster (Au NC ) sensor. The fluorescent intensity of Au NCs with metal cations can be restored by chelating with ethylenediaminetetraacetic acid except for Hg²⁺ ions. A highly selective detection of Hg²⁺ ion is also achieved under the coexistence of Fe³⁺ or Cr³⁺ ions. This assay was applied successfully for detecting Hg²⁺ in a water sample. The dynamic range of the system was 1 ppm to 25 ppb, and the limit of detection was 25 ppb.     

Trinuclear Gold Clusters Supported by Cyclic (alkyl)(amino)carbene Ligands: Mimics for Gold Heterogeneous Catalysts

The synthesis of air‐ and moisture‐stable trinuclear mixed‐valence gold(I)/gold(0) clusters is described. They promote the catalytic carbonylation of amines under relatively mild conditions. The synthetic route leading to the trinuclear clusters involves a simple ligand exchange from the readily available μ³‐oxo‐[(Ph₃PAu)₃O]⁺ complex. This synthetic method paves the way for the preparation of a variety of mixed‐valence gold(I)/gold(0) polynuclear clusters. Moreover, the well‐defined nature of the complexes demonstrates that the catalytic process involves a rare example of a definite change of oxidation state of gold from Au⁰₂Au^I to Au^I₃.     

DFT Study of Charge Effect on the Odd-even Oscillatory Behavior in Stabilities for Gold Clusters

The comparative study of charge effect on the size-dependence stabilities of gold clusters Aunz(n = 2~12, z = 0/±1) in gas phase is performed at the M06-L/Lanl2 dz level. The lowest-energy structures charged by –1, 0 and +1 are optimized. The result shows that the geometries of the clusters with over 7 atoms tend to be cake-like. From the two- to three-dimensional geometries, the oscillatory behaviors are exhibited in the structural and electronic properties with the most pronounced in energy gap. The amplitude for the positive clusters is bigger than both the neutral and negative clusters. The neutral clusters with even number of even-coordinated atoms are more stable than the neighbors with odd number of even-coordinated atoms, as is completely reversed for the charged clusters. The oscillatory behaviors for the charged clusters are opposite to that for the neutral clusters, as is attributed to the electron-paired effect.     

The Effect of Solvation on Electron Attachment to Pure and Hydrated Pyrimidine Clusters

The interaction of low‐energy electrons with biomolecules plays an important role in the radiation‐induced alteration of biological tissue at the molecular level. At electron energies below 15 eV, dissociative electron attachment is one of the most important processes in terms of the chemical transformation of molecules. So far, a common approach to study processes at the molecular level has been to carry out investigations with single biomolecular building blocks like pyrimidine as model molecules. Electron attachment to single pyrimidine, as well as to pure clusters and hydrated clusters, was investigated in this study. In striking contrast to the situation with isolated molecules and hydrated clusters, where no anionic monomer is detectable, we were able to observe the molecular anion for the pure clusters. Furthermore, there is evidence that solvation effectively prevents the ring fragmentation of pyrimidine after electron capture.     

Au108S24(PPh3)16: A Highly Symmetric Nanoscale Gold Cluster Confirms the General Concept of Metalloid Clusters

The reduction of (Ph₃P)AuCl with NaBH₄ in the presence of HSC(SiMe₃)₃, leads to one of the largest metalloid gold clusters: Au₁₀₈S₂₄(PPh₃)₁₆ ( 1 ). Within 1 an octahedral Au₄₄ core of gold atoms arranged as in Au metal is surrounded by 48 oxidized Au atoms of an Au₄₈S₂₄ shell, a novel building block in gold chemistry. The protecting Au₄₈S₂₄ shell is completed by additional 16 Au(PPh₃) units, leading to a complete protection of the gold core. Within 1 the Au–Au distances get more molecular on going from the center to the ligand shell. Cluster 1 represents novel structural motives in the field of metalloid gold clusters which also are partly typical for metal atoms in metalloid clusters: M_n R_m (n >m ).     

Gas Phase Ion Chemistry of Transition Metal Clusters: Production, Reactivity, and Catalysis

This review focuses on the use of mass spectrometry to examine the gas phase ion chemistry of metal clusters. Ways of forming gas phase clusters are briefly overviewed and then the gas phase chemistry of silver clusters is discussed to illustrate the concepts of magic numbers and how reactivity can be size dependent. The chemistry of other bare and ligated metal clusters is examined, including mixed metal dimer ions as models for microalloys. Metal clusters that catalyze gas phase chemical reactions such as the oxidation of CO and organic substrates are reviewed. Finally the interface between nanotechnology and mass spectrometry is also considered.     

Synthesis of Subnanometer‐Sized Gold Clusters by a Simple Milling‐Mediated Solid Reduction Method

An effective solvent‐free method based on a solid‐reduction process was developed to fabricate ultrafine gold catalysts. By this method we revealed a strong size‐dependent activity of Au species in which subnanometer‐sized clusters exhibited the best activity in the hydrogenation of CO₂ to formate, with a turnover number of up to 9278 over 7 h at 90 °C.     

马来酸氯本那敏与7,7,8,8-四氰基对二次甲基苯醌的荷移反应

以马来酸氯本那敏 (商品名扑尔敏 )作为电荷给体 ,7,7,8,8 四氰基对二次甲基苯醌 (TCNQ)作为电子受体 ,研究了它们之间形成电荷转移络合物的最佳条件。结果表明 :在丙酮介质中 ,二者于室温 (2 0℃ )下 30min即可形成 1∶2络合物 ,室温下至少稳定 2h。络合物的最大吸收波长为 84 5nm。表观摩尔吸光系数ε为4 6 3× 10 4L·mol-1·cm-1,在 0～ 6mg/L范围内符合比尔定律。方法的相对标准偏差为 1.2 % (n =10 )。对形成荷移络合物的机理进行了探讨 ;用拟定的方法对片剂样品中马来酸氯本那敏的含量进行了测定 ,结果与药典方法一致 ,回收率符合要求