Synchrotron-Radiation Photoemission Study of Growth and Stability of Au Clusters on Rutile TiO2（110）-1×1

The growth and thermal stability of Au clusters on a partially-reduced rutile TiO2 （110）-1 × 1 surface were investigated by high-resolution photoelectron spectroscopy using synchrotron- radiation-light. The valence-band photoelectron spectroscopy results demonstrate that the Ti^3＋3d feature attenuates quickly with the initial deposition of Au clusters, implying that Au clusters nucleate at the oxygen vacancy sites. The Au4f core-level photoelectron spectroscopy results directly prove the existence of charge transfer from oxygen vacancies to Au clusters. The thermal stability of Au clusters on the partially-reduced and stoichiometric TiO2（110） surfaces was also comparatively investigated by the annealing experiments. With the same film thickness, Au clusters are more thermally stable on the partially-reduced TiO2（110） surface than on the stoichiometric TiO2（110） surface. Meanwhile, large Au nanoparticles are more thermally stable than fine Au nanoparticles.

Computer simulation of Au clusters properties

An alternate approach to parametrizing the expression for the total energy of Au clusters within the second moment approximation (SMA) of the tight binding (TB) theory has been described. A type of many body interatomic potential for Au from first principle’s calculations has been constructed. The key of the approach is adjusting the total-energy expression of the TB SMA method to augmented plane wave (APW) total energy results. The lattice constant, melting temperature, and the bulk modulus are in agreement with available experimental values. The method and results of Au cluster properties are shown to be very useful and suitable in describing the clusters and bulk metals.

In situ Synthesis of Ultrasmall Au Clusters on Thiol-modified CeO_(2) with Enhanced Stability and CO Oxidation Activity

Gold(Au)nanoclusters supported on various supports have been widely used in the fields of energy and catalysis.However,the poor thermal stability of Au nanoclusters on the support interface usually leads to a reduction or even loss of catalytic activity.Herein,we used an in situ reduction method to synthesize Au nanoclusters on ceria(CeO_(2))carriers.In this method,sulfhydryl groups were used to modify CeO_(2) nanospheres first,and then Au clusters with an average diameter of 1.5 nm were grown on the surface of ceria reduced with sodium borohydride.The presence of the Au-S-Ce structure enhances the electron transfer efficiency,making the material exhibit high CO oxidation activity at room temperature.Furthermore,due to the strong binding energy of S and Au,the material exhibits a high stability for long time running process.This strategy provides an idea for designing stable and active supported ultrasmall Au nanoclusters catalytic materials.

Au cluster anchored on TiO_(2)/Ti_(3)C_(2) hybrid composites for efficient photocatalytic CO_(2) reduction

The size of metal nanoparticles is a key factor to enhance the photocatalytic activity of photocatalysts.However,the mechanism of this factor to the improvement of photocatalytic CO_(2) reduction performance is still unclear.Here,Au cluster/TiO_(2)/Ti_(3)C_(2) and Au nanoparticle/TiO_(2)/Ti_(3)C_(2) were successfully prepared by deposition-precipitation method.The experimental results show that the photocatalytic CO_(2) reduction performance of Au cluster/TiO_(2)/Ti_(3)C_(2) with quantum size effect is stronger than that of Au nanoparticle/TiO_(2)/Ti_(3)C_(2) with surface plasmon resonance.The enhanced photocatalytic CO_(2) reduction activity is assigned to the establishment of an overlapping orbital between the lowest unoccupied molecular orbital(LUMO)of the Au cluster and the anti-bonding orbital of CO_(2),which greatly promotes the activation efficiency of CO_(2).The existence of Au cluster and the mechanism of photocatalytic CO_(2) reduction performance were certified by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and in situ Fourier transform infrared spectroscopy(ISFTIR).This work may open new opportunities for the establishment of stable and active metal nanocatalysts.

Ag_(24)Au cluster decorated mesoporous Co_(3)O_(4)for highly selective and efficient photothermal CO_(2)hydrogenation

Photothermal carbon dioxide hydrogenation represents a promising route to reduce the emission of greenhouse gas CO_(2)and produce value-added chemicals,but the selectivity and stability of photothermal catalysts need to be improved.Herein,we report the rational fabrication of well-defined Ag_(24)Au cluster decorated highly ordered nanorod-like mesoporous Co_(3)O_(4)(Ag_(24)Au/mesoCo_(3)O_(4))for highly efficient and selective CO_(2)hydrogenation.The orderly assembled meso-Co_(3)O_(4)nanorods were prepared via a nanocasting method,offering large surface area and abundant active sites for CO_(2)adsorption and conversion.Moreover,the catalytic activity and selectivity were further improved by molecule-like Ag_(24)Au cluster decoration and reaction temperature optimization.The Ag_(24)Au/meso-Co_(3)O_(4)composite catalyst exhibited an ultrahigh CH_(4)yield rate of 204 mmol·g^(−1)·h^(−1)and a greatly improved CH_(4)selectivity of 82%for CO_(2)hydrogenation,significantly higher than those of pristine meso-Co_(3)O_(4)catalyst.The mechanism of the photothermal catalytic performance improvement was verified by CO_(2)temperature-programmed desorption and time-resolved transient photoluminescence,revealing that CO_(2)molecules underwent a vigorous adsorption and rapid activation process over Ag_(24)Au/meso-Co_(3)O_(4).The hot electrons created by the localized surface plasmon resonance effect of Ag_(24)Au clusters facilitated the charge transfer for subsequent multi-electron CO_(2)hydrogeneration processes,resulting in a significant increase in the productivity and selectivity for CO_(2)-to-CH_(4)conversion.This work suggests that the rational coupling of well-defined metal atom clusters and ordered transition metal compound nanostructures could open a new avenue towards photoinduced green chemistry processes for efficient CO_(2)recycling and reutilization.

Specific detection and effective inhibition of a single bacterial species in situ using peptide mineralized Au cluster probes

Increasingly serious microbial infections call for the development of new simpler methods for the precise diagnosis and specific inhibition of such pathogens. In this work, a peptide mineralized Au cluster probe was applied as a new simplified strategy to both recognize and inhibit a single bacteria species of Staphylococcus aureus(S. aureus) simultaneously. The probes are composed of peptides and Au clusters. Moreover, the peptides specifically target S. aureus cells and the Au clusters provide fluorescent imaging and have an antibacterial effect. These new probes enable the simultaneous specific detection and effective destruction S. aureus cells in situ.

Adsorption and Hydrogenation Process of p-Chloronitrobenzene on Au_(20)Cluster:a DFT Study

We have systematically investigated the adsorption and hydrogenation process of p-chloronitrobenzene on Au20 cluster using density functional theory-DFT） calculations.The adsorption of two types of all species,vertical adsorption and parallel adsorption,is compared,revealing that former model is more stable than the latter,and all of the species prefer to adsorb at the vertex site.After adsorption,electrons transferred from Au20 cluster to the p-chloronitrobenzene molecule.Almost all hydrogenation processes are exothermic,and the C–Cl bond scissions are considered as the rate-limiting step for both Paths A-p-CNB→p-CAN→AN） and B-p-CNB→NB→AN） with the energy barriers of 2.62 and 2.95 e V,respectively.These suggest that the C–Cl bond scission is not easy to occur on Au20 cluster due to the high energy barrier,especially the path B.The p-chloroaniline is the main hydrogenation product catalyzed by Au20.

Density functional study of Au_nCu (n=1-7) clusters

The possible stable geometrical configurations and the relative stabilities of the lowest-lying isomers of copperdoped gold clusters, AunCu （n = 1-7）, are investigated using the density functional theory. Several low-lying isomers are determined. The results indicate that the ground-state AunCu clusters have planar structures for n = 1-7. The stability trend of the AunCu clusters （n = 1-7）, shows that odd-numbered AunCu clusters are more stable than the neighbouring even-numbered ones, thereby indicating the AusCu clusters are magic cluster with high chemical stability.

A comparative study on geometries,stabilities,and electronic properties between bimetallic Ag_nX(X=Au,Cu; n=1-8) and pure silver clusters

Using the meta-generalized gradient approximation （meta-GGA） exchange correlation TPSS functional, the geo-metric structures, the relative stabilities, and the electronic properties of bimetallic AgnX （X=Au, Cu; n=1-8） clusters are systematically investigated and compared with those of pure silver clusters. The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n = 6 for the AgnAu clusters, and at n = 5 for AgnCu clusters. For different-sized AgnX clusters, one X （X=Au or Cu） atom substituted Agn＋l structure is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied molecular orbital-lowest unoccupied molecular orbital （HOMO LUMO） energy gaps show interesting odd-even oscillation behaviours, indicating that Ag2,4,6,s and Agl,3,5,7X （X=Au, Cu） clusters keep high stabilities in comparison with their neighbouring clusters. The natural population analysis reveals that the charges transfer from the Agn host to the impurity atom except for the Ag2Cu cluster. Moreover, vertical ionization potential （VIP）, vertical electronic affinity （VEA）, and chemical hardness （η） are discussed and compared in depth. The same odd even oscillations are found for the VIP and η of the AgnX （X=Au, Cu; n=1-8） clusters.

THE GEOMETRY AND ORBITAL INTERACTION OF TRIATOMIC CLUSTERS FOR Cu,Ag,Au(Ⅱ)

In the previous paper,the geometry of the triatomic clusters for Cu, Ag,and An was obtained using the Dy-Xa method. In this investigation the atomic. orbital interactions of atom Cu, Ag, An in the triatomic clusters are analyzed. The magnitudes of the atomic orbital interactions of the atoms in the clusters are measured by the splitting of corresponding atomic orbital. The calculation results show the atomic orbital interactions of Cu triatomic cluster differ greatly from those of Ag and Au triatomic cluster house of the mixture radio of 4s-Orbital with 3d-Orbital in the Cu cluster more than those in the Ag and Au cluster. The values of atomic orbital interactions of Au in the of cluster are larger than corresponding atomic Orbital interactions of Ag in the cluster.

Au_n(n=2～20)团簇的遗传算法和密度泛函方法研究

在遗传算法和Gupta多体势系统地搜索金属团簇初始结构基础上,应用密度泛函理论和基于局域密度近似(LDA)或广义梯度近似(GGA)的超软赝势和投影扩充波(PAW)方法分别系统地研究了金属团簇Aun(n≤20)的最稳定构型和电子性质.发现LDA或GGA近似下,最稳定构型存在一定的差异:LDA方法中,Au团簇最稳定构型从Au7处就发生了从二维结构向三维结构的转化,而GGA近似下Au13的最稳定异构体仍然保持平面构型.计算结果表明,平均最近邻距、平均配位数和结合能随着尺寸的增大呈递增趋势,而二阶差分能、费米能级、HOMO-LUMO能隙、垂直电离势和电子亲和势出现了明显的奇偶交替现象.其结果丰富了目前对金团簇的理论和实验的研究.

O与O_2在Au团簇上吸附的密度泛函理论研究

采用基于密度泛函理论(DFT)的Dmol3程序系统研究了O原子与O2在Au19与Au20团簇上的吸附反应行为.结果表明:O在Au19团簇顶端洞位上的吸附较Au20强;在侧桥位吸附强度相近.O与O2在带负电Au团簇上吸附较强,在正电团簇吸附较弱.从O―O键长看,当金团簇带负电时,O―O键长较长,中性团簇次之,正电团簇中O―O键长较短,因而O2活化程度依次减弱.电荷布居分析表明,Au团簇带负电时,O与O2得电子数较中性团簇多,而团簇带正电时,得电子数较少.差分电荷密度(CDD)表明,O2与Au团簇作用时,金团簇失电子,O2的π*轨道得电子,使O―O键活化.O2在Au-19团簇上解离反应活化能为1.33eV,较中性团簇低0.53eV;而在Au+19上活化能为2.27eV,较中性团簇高0.41eV,这与O2在不同电性Au19团簇O―O键活化规律相一致.

纳米Au团簇在氧化钛修饰的介孔分子筛MCM-41中的组装

以钛酸丁酯为ＴｉＯ２前驱体，使ＴｉＯ２均匀分散于纯硅介孔分子筛ＭＣＭ－４１的介孔孔道内表面，利用ＴｉＯ２光学性质将ＡｕＣｌ－４还原为Ａｕ（０）并组装于氧化钛修饰的ＭＣＭ－４１孔道中．对所合成的Ａｕ负载的氧化钛修饰的ＭＣＭ－４１进行了ＸＲＤ，ＸＰＳ，Ｎ２吸附－脱附曲线，及固体ＵＶ－Ｖｉｓ漫反射等多种结构表征．由ＸＰＳ谱和固体ＵＶ－Ｖｉｓ漫反射吸收光谱的ｐｌａｓｍｏｎ吸收峰证明Ａｕ团簇呈现０价的金属状态．

Cu_n、Ag_n和Au_n(n≤9)团簇的静电极化率(英文 )

采用B3LYP密度泛函的方法计算了Cun,Agn和Aun(n≤9)团簇的静电极化率和极化率的各向异性, 并与Na原子团簇进行比较,结果表明,Cun和Agn团簇的极化率与团簇大小的关系与Na原子团簇类似,而Aun团 簇的极化率有所不同;Au原子的极化率较小,而从Au2至Au7,Aun团簇极化率变化趋势与Cun和Agn团簇相似。 重金属元素团簇的极化率小于Na原子团簇的极化率,具有更加紧致结构。

Au_n(n=2-9)团簇与乙醇分子相互作用的第一性原理研究

利用密度泛函理论研究了Aun(n=2-9)团簇吸附一个乙醇分子的结构和电子性质.研究结果表明:Aun(n=2-9)团簇的最稳定构型为二维平面结构,Au6团簇最稳定;吸附过程是通过金团簇上一个特定的金原子与乙醇分子中氧原子相互作用完成,形成了20种稳定构型;金原子的配位数对吸附作用影响明显;作为吸附主体的金团簇和被吸附的乙醇分子在吸附前后构型无明显变化,它们之间为弱相互作用.

Au_nPd(n=1~5)团簇的第一原理研究(英文)

用基于密度泛函理论的第一原理方法研究二元混合团簇AunPd（n=1～5）的稳定结构,得到团簇各种稳定结构的几何构形和对应的电子态,与纯Aun团簇比较研究了混合团簇AunPd（n=1～5）的稳定性.结果表明：AunPd（n=1～5）混合团簇具有多种稳定的异构体,部分异构体具有较高的自旋多重性.在Aun团簇中掺入Pd原子后,Au-Pd间的强相互作用改变了团簇的稳定结构,这种变化随团簇体积的增大而减小.

Au_nY(n=1-5)团簇的结构与稳定性研究

用相对论有效原子实势(RECP)和密度泛函(B3LYP)理论,选择LANL2DZ基组研究了AunY(n=1-5)团簇的各种几何结构及稳定性。结果表明AuY、Au2 Y和Au3 Y团簇的基态几何构型是平面结构,Au4 Y和Au5 Y的基态构型是三维结构。通过计算原子平均结合能、二阶差分能量、破碎能量及能级间隙判断AunY(n=1-5)团簇稳定趋势,结果表明Au3Y是幻数团簇,具有较高的化学稳定性。

冷速对Au熔体凝固组织影响的分子动力学模拟

为了研究液态金属Au凝固后微观结构随冷速的变化规律,通过分子动力学方法模拟液态金属Au的凝固组织,利用径向分布函数和HA键型指数法对最终构型进行分析.模拟结果表明:冷速在1.0×10^(11.0)~1.0×10^(14.5) K·s^(-1)之间时,Au熔体凝固后形成由晶体结构和非晶态结构组成的混合组织;冷速大于1.0×10^(14.5) K·s^(-1)时,凝固后形成非晶态组织.最大晶体团簇中,FCC结构原子随着冷速的增加而变少,HCP结构原子数量随着冷速的增加先增多后减少.

配体保护下的Au_8团簇吸附和活化O_2的第一性原理研究

采用密度泛函理论的TPSS泛函,研究在配体聚乙烯吡咯烷酮(poly(N-vinyl-2-pyrrolidone),PRD)保护下O2吸附在Au8团簇上的稳定构型的结构和电子性质。PRD通过物理吸附作用在Au8团簇上,PRD中的O与Au8形成较弱的Au-O键。相对于Au8团簇,Au8∶PRD n团簇的活性略有提高并与O2产生共吸附效应。分析表明:在共吸附中,PRD通过Au8将部分电子转移给了O2,进入了O2的LUMO轨道,促进了Au对O2的活化作用,从而提高了Au8的催化活性。