Nanogymnastics: Visualization of Intercluster Reactions by High-Resolution Trapped Ion Mobility Mass Spectrometry (original) (raw)
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Journal of the American Chemical Society, 2021
The kinetics of intercluster metal atom exchange reactions between solvated [Ag 25 (DMBT) 18 ] − and [Au 25 (PET) 18 ] − (DMBT and PET are 2,4dimethylbenzenethiol and 2-phenylethanethiol, respectively, both C 8 H 10 S) were probed by electrospray ionization mass spectrometry and computer-based modeling. Anion mass spectra and collision induced dissociation (CID) measurements show that both cluster monomers and dimers are involved in the reactions. We have modeled the corresponding kinetics assuming a reaction mechanism in which metal atom exchange occurs through transient dimers. Our kinetic model contains three types of generic reactions: dimerization of monomers, metal atom exchange in the transient dimers, and dissociation of the dimers to monomers. There are correspondingly 377 discrete species connected by in total 1302 reactions (i.e., dimerization, dissociation and atom exchange reactions) leading to the entire series of monomeric and dimeric products [Ag m Au 25−m ] − (m = 1−24) and [Ag m Au 50−m ] 2− (m = 0−50), respectively. The rate constants of the corresponding reactions were fitted to the experimental data, and good agreement was obtained with exchange rate constants which scale with the probability of finding a silver or gold atom in the respective monomeric subunit of the dimer, i.e., reflecting an entropic driving force for alloying. Allowing the dimerization rate constant to scale with increasing gold composition of the respective reactants improves the agreement further. The rate constants obtained are physically plausible, thus strongly supporting dimer-mediated metal atom exchange in this intercluster reaction system.
Size-Dependent Structural Evolution and Chemical Reactivity of Gold Clusters
ChemPhysChem, 2007
Ground-state structures and other experimentally relevant isomers of Au 15 À to Au 24 À clusters are determined through joint firstprinciples density functional theory and photoelectron spectroscopy measurements. Subsequent calculations of molecular O 2 adsorption to the optimal cluster structures reveal a size-dependent reactivity pattern that agrees well with earlier experiments. A detailed analysis of the underlying electronic structure shows that the chemical reactivity of the gold cluster anions can be elucidated in terms of a partial-jellium picture, where delocalized electrons occupying electronic shells move over the ionic skeleton, whose geometric structure is strongly influenced by the directional bonding associated with the highly localized "d-band" electrons.
Journal of Physical Chemistry C, 2010
Relativistic density functional theory (DFT) based calculations have been performed on gold clusters with six to thirteen atoms (Au n ; n ) 6-13). The ground state geometries of these clusters as obtained from our calculations are presented and discussed. This work proposes that atoms in a ground state conformation can be classified into distinct types of reactive sites in a given geometry. Based on symmetry, susceptibility of various types of reactive sites in the ground state geometry toward an impending electrophilic and/or a nucleophilic attack has also been studied using DFT based reactivity descriptors. The studies have also been extended to high energy isomers in these cluster sizes. The reactivity of various sites as a function of cluster size and shape was thus analyzed. The study shows that as a general rule the size and shape of the cluster influences the number and position of available sites for an electrophilic and/or nucleophilic attack. This makes the reactivity patterns of these clusters highly complex. The study also highlights as to how for a cluster with seven atoms (Au 7 ) various conformations are likely to coexist indicating that the reactivity patterns of various high energy conformations are also important while dealing with small sized Au clusters.
Zeitschrift für anorganische und allgemeine Chemie, 2011
The outstanding position of metalloid clusters as intermediates between the bulk metals and bulk salts on the one hand and of naked metal atom clusters and salt-like clusters on the other hand is described first. Subsequently, a different more chemical description of structure and bonding of a recently published gold-thiolate Au 102 (SR) 44 cluster based on the results of aluminum-/gallium clusters is presented. This comparison shows that there is no principal but only a gradual difference between the Au 102 cluster and the large number of metalloid aluminum-/gallium clusters: both have a metalloid character, i.e. there is a highly mixed valent bonding situation of the metal atoms involved. Therefore these clusters represent a highly complex system and are far from being only nanoscaled metal particles surrounded by a shell of protecting ligands. In detail this comparison shows that the metalloid gold and the aluminum-/gallium clusters are similar in the center, as these metal-metal interactions are energetically similar to those of the
ACS nano, 2017
Monolayer protected clusters exhibit rich diversity in geometric and electronic structures. However, structure-reactivity relationships in these clusters are rarely explored. In this context, [Ag44(SR)30](4-), where -SR is an alkyl/aryl thiolate, is an interesting system due to its geometrically and electronically closed-shell structures and distinct charge states. We demonstrate that these structural features of [Ag44(SR)30](4-) are distinctly manifested in its solution-state reaction with another cluster, [Au25(SR)18](-). Through this reaction, an alloy cluster anion, [Au12Ag32(SR)30](4-), evolves spontaneously as revealed by high-resolution electrospray ionization mass spectrometry. Ultraviolet-visible absorption spectroscopy and density functional theory calculations indicate that [Au12Ag32(SR)30](4-) is formed by the substitution of all of the Ag atoms in the innermost icosahedral shell of [Ag44(SR)30](4-) and the abundance is attributed to its higher stability due to closed ge...
ChemPhysChem, 2015
Gold solid skins [1-4] and atomic clusters [5-11] have attracted much attention because of their fascinating properties that are barely seen in bulk Au. For example, Au atomic clusters have high catalytic activity [12-16] for CO and H 2 oxidation, [17] even thoughb ulk Au is noble and chemically stable. During exposure to O 3 ,a no xide is formed on the surface of Au foil, which modifies its properties. [18] The 4f core level of Au surfaces [19-22] shifts in an orientation-dependentm anner.Adecrease in the cluster size monotonically deepens the energy level by af ew eVs. These unusual properties arise from interactions between undercoordinated atoms, because atomic undercoordination relaxest he local bond and electronic attributes, which determine the catalytic, [23] magnetic, [24] mechanical, [25] and thermal [26] properties of materials. [27] However,q uantitative information and ac onsistent understandingo ftheb ond and electronic attributes and their correlation remainint heir infancy.
Theoretical Analysis of Au38-xPtx and Au38-xAgx(x=1-19) Bimetallic Clusters
2018
Global optimization of thirty eight Au38-xPtx and Au38-xAgx bimetallic clusters (x=1-19) has been performed using basin hopping algorithm and the manybody Gupta empirical potential (EP) to model interatomic interactions by combined empirical potential (EP)-density functional (DF) approach. Vibrational analysis has been carried out to check the stability of the doped metal clusters. The thermal and chemical stability are measured by binding energy and HOMO-LUMO gap. The excess energy, mixing energy, mixing coefficient, average binding energy, order parameter, shape deformation parameter and average nearest neighbor distance (ANND) are calculated for these doped clusters. The surface segregation of the most cohesive element (Pt) into the core is seen in Au38-xPtx clusters. Ag atoms occupy place in both core and shell for Au38-xAgx clusters, while charge transfer effect favors the segregation of Au to the surface of the reported clusters. The Au surface segregation is preferred for Au3...
Intercluster Reactions between Au25(SR)18 and Ag44(SR)30
Journal of the American Chemical Society, 2016
We present the first example of intercluster reactions between atomically precise, monolayer protected noble metal clusters using Au25(SR)18 and Ag44(SR)30 (RS- = alkyl/aryl thiolate) as model compounds. These clusters undergo spontaneous reaction in solution at ambient conditions. Mass spectrometric measurements both by electrospray ionization and matrix assisted laser desorption ionization show that the reaction occurs through the exchange of metal atoms and protecting ligands of the clusters. Intercluster alloying is demonstrated to be a much more facile method for heteroatom doping into Au25(SR)18, as observed by doping up to 20 Ag atoms. We investigated the thermodynamic feasibility of the reaction using DFT calculations and a tentative mechanism has been presented. Metal core-thiolate interfaces in these clusters play a crucial role in inducing these reactions and also affect rates of these reactions. We hope that our work will help accelerate activities in this area to establ...
The Journal of Physical Chemistry A, 2003
We report a joint experimental and theoretical study of the electronic and atomic structures of small gold clusters with up to 14 atoms. Well-resolved photoelectron spectra were obtained for Au N -(N ) 1-14) at several photon energies. Even-odd alternations were observed, where the even-sized clusters (except Au 10 -) exhibit an energy gap between the lowest binding energy peak and the rest of the spectrum, indicating that all the neutral even-sized clusters have closed shells. The Au 10spectrum reveals the existence of isomers, with the ground-state cluster exhibiting an extremely high electron binding energy. Evidence of multiple isomers was also observed in the spectra of N ) 4, 8, 12, and 13. The structures of the gold cluster anions in the range N ) 4-14 were investigated using first-principles simulations. A striking feature of the anionic clusters in this range is the occurrence of planar ground-state structures, which were predicted in earlier theoretical studies et al. Phys. ReV. Lett. 2002, 89, 033401) and observed in ion-mobility experiments et al. J. Chem. Phys. 2002, 117, 6982) and the existence of close-lying isomers. The calculated electron detachment energies and density of states were compared with the measured data, which confirmed the ground-state structures of the anions. It is found that the main isomers observed experimentally indeed consist of planar clusters up to Au 12 -, whereas for Au 13and Au 14the theoretical results from threedimensional isomers agree better with the experiment, providing further support for the 2D to 3D structural transition at Au 12 -, as concluded from previous ion mobility experiments. We also find that small neutral clusters exhibit a tendency to form two-dimensional structures up to a size of 13 atoms.