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.

Targeted peptide-Au cluster binds to epidermal growth factor receptor (EGFR) in both active and inactive states： a clue for cancer inhibition through dual pathways

The epidermal growth factor receptor(EGFR) has become an important target protein in anticancer drug development. Meanwhile, peptide-Au cluster has been proposed as potential targeted nano-drug assembled by targeting peptide. Here, we designed and synthesized a novel peptide-Au cluster as Au_(10)Peptide_5 to target to EGFR. We found Au_(10)Peptide_5 could target to the natural binding sites of all EGFRs at membrane in both active and inactive states by molecular simulations. Its targeted ability was further verified by the co-localization and blocking experiments. We also study the configuration modifications of both active and inactive EGFRs after binding by Au_(10)Peptide_5. For active EGFR, the absorbed Au_(10)Peptide_5 might replace the natural ligand in EGFR endocytosis process. Then, the peptide-Au cluster in endochylema could inhibit the cancer relating enzyme activity including thioredoxin reductase1(TrxR1) and induce the oxidative stress mediated apoptosis in tumor cells. For inactive EGFR, it was retained in inactive state by Au_(10)Peptide_5 binding to inhibit dimerization of EGFR for anticancer. Both pathways might be applied in anticancer drug development based on the theoretical and experimental study here.

Bio-inspired peptide-Au cluster applied for mercury(II) ions detection

Mercury ion(Hg2+) pollution exists in water, soil, and food. By interacting with the thiol groups in protein, Hg2+ ions can accumulate in ways that cause serious damage to the central nervous system and threaten human health and natural environment. Undoubtedly, Hg2+ ion detection is a significant issue in environment and health monitoring. A variety of sensor platforms for Hg2+ ion detection based on organic molecules, DNA, oligonucleotides, inorganic materials, etc, have been reported. In this paper, an artificial peptide PHg, with a cluster bio-mineralize sequence(CCY) and a multi-charge hydrophilic sequence is designed as a template for the one-step synthesis of a peptide-Au cluster probe. Briefly: the peptide PHg in situ anchors Au ions to form a peptide-Au(I) intermediate and the reaction p H with Na OH is adjusted; after 12 h incubation at room temperature, the peptide PHg-Au nanocluster probe with red fluorescence is obtained. The probe has a super-small core size of approximately 1.26 nm and a maximum emission peak at 650 nm. The presence of Hg2+ ions cause the fluorescence of the probe to greatly decrease. Based on the differences in fluorescence intensity of the PHg-Au nanocluster in the absence and presence of Hg2+ ions, Hg2+ ions could be quantitatively detected in concentrations ranging from 5 nmol/L to 1 ?mol/L. The limit of detection(LOD) is 7.5 nmol/L. Compared with some interference ions such as, K+, Mg2+, Ca2+, Pb2+, Ni2+, Fe3+, and Cu2+, the selectivity was excellent. The sensing of Hg2+ ion is not affected by the chelate agents: EDTA, which imparts a significant advantage in a range of applications. As a result, a simple, sensitive and selective fluorescent assay based on peptide PHg-Au cluster is developed for the detection of Hg2+ ions.

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.

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.

CRYSTAL AND MOLECULAR STRUCTURE OF A NOVEL Au Ag SUPRACLUSTER COMPOUND [Au_13Ag_12(μ-Br)_4(μ_3-Br)_2(Ph_3P)_10-

[Au13Ag12(μ-Br)1(μ3-Br)2 (Ph3P)10Br2] Br, monoclinic. space group C2/m, a = 36. 496(17). b=16. 878(7), c-=19. 772(9) A , β=99. 87(5)°, V=11998. 9 A3.Z=2. The final R(Rw) is 0. 097(0. 109) for 3779 reflections with I>3σ(I). The structure can he considered as two icosahedral cluster units (AurAg6) sharing one vertex and linked hy six bromine atoms. The Au - Au, Au - Ag. and Ag-Ag distances fall in the ranges of 2. 69-2. 96. 2. 84-3. 02. and 2. 92-3. 26 A, respectively.

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。