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[Display omitted] • A comprehensive summary of advances in metal cluster superatoms. • Superatomic features of transition metal clusters, electronic open- and closed shells, aromaticity, and magnetism. • A summary of the principles and theoretical modeling around superatoms. • A four-dimensional image for the 3D periodic table of elements, providing convenience for tailoring cluster-genetic materials. Clusters that mimic elemental atoms in the periodic table are known as superatoms which open up a new window to design functional materials and catalysts by atomic construction. Ongoing continuous efforts have been devoted to exploring active/inert superatoms in the gas phase and synthesizing ligand-protected metal cluster superatoms and superatomic solids. Here we summarize recent research progress of superatom chemistry and elucidate the accommodation of delocalized electrons in stabilizing metal clusters, especially the superatomic orbitals formed by d-electrons of the transition metals. We highlight the typical superatomic features of electronic open- and closed shells, aromaticity, and magnetism especially for the clusters of nonmagnetic elements. We propose a four-dimensional image for the future three-dimensional periodic table of elements, endeavoring to provide a convenient reference for designing and tailoring cluster-genetic materials. [ABSTRACT FROM AUTHOR]

Three hydrogen-bonded organic–inorganic frameworks (HOIFs) are synthesized. Along with full characterization and a comparison with similarly synthesized deuterated counterparts, we reveal that hydrogen-bond interactions of the HOIFs dominate the thermostability, porosity and selectivity in dye filtration on alumina membranes. [ABSTRACT FROM AUTHOR]

Isolated clusters are ideal systems for tailoring molecule-based magnets and investigating the evolution of magnetic order from microscopic to macroscopic regime. We have prepared pure Fen– (n = 7-31) clusters and observed their gas-collisional reactions with oxygen in a flow tube reactor. Interestingly, only the larger Fen– (n ≥ 15) clusters support the observation of O2-intake, while the smaller clusters Fen– (n = 7-14) are nearly nonreactive. What is more interesting is that Fe17O10– shows up with prominent abundance in the mass spectra indicative of its distinct inertness. In combination with DFT calculations, we unveil the stability of Fe17O10– within an interesting acordion-like structure and elucidate the spin accommodation in such a strongly ferromagnetic iron cluster oxide. Iron oxide nanoclusters have high potential for high-density energy storage and spintronics microdevices, but systems that are both stable and display strong ferromagnetism remain challenging to obtain. Here, the authors study the gas phase collision reactions of the iron clusters Fen- (n = 7-31) and observe the stable, strongly ferromagnetic iron oxide cluster Fe17O10- featuring an accordion-like structure. [ABSTRACT FROM AUTHOR]

Isolated clusters are ideal systems for tailoring molecule-based magnets and investigating the evolution of magnetic order from microscopic to macroscopic regime. We have prepared pure Fen– (n = 7-31) clusters and observed their gas-collisional reactions with oxygen in a flow tube reactor. Interestingly, only the larger Fen– (n ≥ 15) clusters support the observation of O2-intake, while the smaller clusters Fen– (n = 7-14) are nearly nonreactive. What is more interesting is that Fe17O10– shows up with prominent abundance in the mass spectra indicative of its distinct inertness. In combination with DFT calculations, we unveil the stability of Fe17O10– within an interesting acordion-like structure and elucidate the spin accommodation in such a strongly ferromagnetic iron cluster oxide. Iron oxide nanoclusters have high potential for high-density energy storage and spintronics microdevices, but systems that are both stable and display strong ferromagnetism remain challenging to obtain. Here, the authors study the gas phase collision reactions of the iron clusters Fen- (n = 7-31) and observe the stable, strongly ferromagnetic iron oxide cluster Fe17O10- featuring an accordion-like structure. [ABSTRACT FROM AUTHOR]

We have investigated the gas-phasereactivity of silver clusterswith ethanethiol in a fast-flow tube reactor. The primary clusterproducts observed in this reaction are AgnSH–and AgnSH2–, indicating C–S bond activation, togetherwith interesting byproducts H3S–and(H3S)2–. Agn–clusters with an odd number of valenceelectrons (n= even) were observed to be more reactivethan those with an even number of electronsa feature previouslyonly observed in the reactivity of Agn–with triplet oxygen, indicating that radicalactive sites play a role in their reactivity. Furthermore, the reactivitydramatically increases with large flow rate of ethanethiol being introducedin the flow tube. Theoretical investigations on the reactivity ofAg13–and Ag8–with ethanethiol indicate that both Ag13–and Ag8–face significant barriersto reactivity with a single ethanethiol molecule. However, Ag8–reacts readily in a cooperative reactionwith two ethanethiol molecules, consistent with the dramatic increasein reactivity with a large flow rate. Further hydrogen-transfer reactionsmay then release an ethylene molecule or an ethyl radical resultingin the observed AgnSH–species. [ABSTRACT FROM AUTHOR]

We present here a study of gas-phasereactivity of cobalt sulfidecluster anions ComSn–with molecular oxygen. Nascent ComSn–clusters were prepared via a laser ablation source and reacted withoxygen in a fast flow reactor under thermal collision conditions.We chose 18O2in place of 16O2to avoid mass degeneration with sulfur, and a time-of-flight(TOF) mass spectrometer was used to detect the cluster distributionsin the absence and presence of the reactant. It was found that oxygen–sulfurexchange occurs in the reactions for those with specific compositions(CoS)n–and (CoS)nS–(n=2–5) according to a consistent pathway, “ComSn– 18O2→ ComSn–118O– S18O”. Typically, for “Co2S2– 18O2”we have calculated the reaction coordinates by employing the densityfunctional theory (DFT), where both the oxygen–sulfur exchangeand SO molecule release are thermodynamically and kinetically favorable.It is noteworthy that the reaction with molecular oxygen (tripletground state) needs to overcome a spin excitation as well as a largeO–O activation energy. This study sheds light on the activationof molecular oxygen by cobalt sulfides on one hand and also providesinsight into the regeneration mechanism of cobalt oxides from thecounterpart sulfides in the presence of oxygen gas on the other hand. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied the gas-phase reactivity of Al clusters with ethanethiol. [•] We observe size dependence of in reacting with ethanethiol. [•] dominate the reaction products indicating C–S bond activation. [•] An in-depth analysis on the cluster reactivity “ +EtSH” is demonstrated. [ABSTRACT FROM AUTHOR]

Highlights: [•] We have improved the method of laser-ablation in liquids (LAL). [•] We prepared metastable gold clusters with only water as media. [•] In-depth analysis on the stability of the gold colloid is demonstrated. [•] We show an application of the gold clusters for surface identification. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied the reactions of coinage metal clusters with chlorine. [•] We observe abnormal reactivity of [Ag8]−/[Cu8]− towards chlorine. [•] We demonstrate the harpoon mechanism for the reactivity of [Ag8]−/[Cu8]− with Cl2. [•] The alkali-metal-like clusters [Ag8]−/[Cu8]− validate the reactivity of superatoms. [ABSTRACT FROM AUTHOR]

We report a surface-enhanced Raman spectroscopy (SERS) investigation to probe the adsorption and dynamic behavior of rhodamine 6 G (Rh6G) molecules on spherical Ag nanoparticles which were produced via laser ablation in liquid. Assembly of the colloidal Ag nanoparticles on a cover glass was used to work as SERS substrates on which high-quality SERS spectra of Rh6G were obtained with interesting time dependence when using low and ultralow concentrations, respectively. The variation of SERS spectra over time was identified with the adsorption behavior of multiple and individual molecules on the Ag nanoparticles. Analysis indicates that the adsorbed Rh6G molecules can desorb away from the initial locations on the substrate under continuous laser excitation; simultaneously, some individual molecules can move and become trapped in the gap between the aggregated Ag nanoparticles. These investigations help to clarify the origins of forming 'hot-spots' which host probe molecules and hence improve the understanding of mechanisms for single-molecule SERS spectroscopy. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We investigated the halogenation reactivity of coppercluster anionsproduced via a magnetron-sputter source after introduction into afast-flow tube reaction apparatus simultaneously with chlorine gas.Interesting cluster products corresponding to [CunCln]−(n= 1–6) were observed with notable stability, andthe mass distribution of these clusters exhibits an exponential decaywith increasing values of n. Reaction kinetics analysisis provided on the gas-phase reactivity of copper cluster anions withchlorine. First-principle calculations suggest a series of cubic-likestructures for these species similar to the structure of alkali halideclusters due to their similar electronic configurations. These structuresact as a starting point in the formation of ionic crystals. [ABSTRACT FROM AUTHOR]

Abstract: A magnetron-sputtering (MagS) cluster source was used to produce metal clusters of different size distributions by varying individual source parameters. Selectivity of the size of the Al clusters was observed and the mass distribution presents wide-range controllability by the MagS-source, which enables experimental determination of the growth process of Al clusters. By implementing the extended Smoluchowski rate equation, here we propose an interpretation of the cluster-growth kinetics in the gas phase environment. A collision-dependent growing time domain is demonstrated. [Copyright &y& Elsevier]

Abstract: Anodic aluminum oxide (AAO) templates were controllably prepared for nano-copy with the controllable aperture from 5nm to 200nm. An unusual method for Iron/Cobalt nanowire arrays to grow directly into the AAO template is introduced, which is not only simple but also can be produced at room temperature at large scale. The rods of crystal Iron/Cobalt grown in the holes of AAO template are obtained, and they are highly ordered quantum arrays and are controllable in size. [Copyright &y& Elsevier]

Abstract: Surface enhanced Raman scattering (SERS) spectra of C60 (C70) were obtained in nonaqueous colloidal systems with newly developed methods. The enhancement factor was estimated to be over 105. This paper aims at the investigation of a fine influence mechanism for SERS in the nonliquid phase, which may help bring forth the perfect SERS mechanism. The detailed investigation is based on abundant comparative experiments where we found that the SERS effect is sensitive not only to the character of colloidal particles, dielectric constants, and polarizability, but also to the substrates, the solvent intermediate, and even the coating techniques. These detailed comparisons enrich the proofs of the SERS mechanism and provide a new way to optimize SERS systems. [Copyright &y& Elsevier]

Abstract: It is important to apply the surface enhanced Raman scattering (SERS) spectra to study the interfacial properties of films and the adsorption behavior of molecules on substrates. In this paper, SERS spectra of good quality of gold/C60 (/C70) nano-clusters deposited on floppy disk and hard disk were reported with the pyridine as a kind of solvent intermediate. The floppy disk or hard disk, as a new and effective substrate for SERS, provides a plank for C60/C70 molecules to adsorb on the gold nano-particles. The number of vibrational modes was greatly increased, especially some modes that were forbidden in Raman spectrum, appeared and even split as prediction of group theory. The enhancement factor is estimated to over 106. It provides convenience for probing the C60/C70 vibrational structure and the physical properties with the high sensitivity, as well as the adsorption behavior, the interaction of fullerene with gold surface and the SERS mechanism of molecules adsorbed on substrates. What’s more, the SERS sensitivity of the magnetism is demonstrated by comparing the SERS of gold/C60 (/C70) nano-clusters deposited on floppy disk and hard disk. [Copyright &y& Elsevier]

Abstract: SERS of C60/C70 adsorbed on gold nanoparticles coated on filter paper or filter film was studied. As a new SERS substrate, dried gold-coated filter paper or filter film has a high SERS activity, whose enhancement factor can be up to about 105, because it avoided the influence of solvents in C60/C70 solution and water in gold hydrosols. The influence of the gold thickness coated on filter paper or filter film to SERS of C60/C70 adsorbed on gold nanoparticles was mainly discussed. It is indicated that the SERS effect of C60/C70 was very sensitive to the distribution and aggregated characteristics of gold nanoparticles, and the SERS intensity of each mode increased at its own proportion, but it integrally tended to saturation when the thickness of colloidal gold coatings increased. [Copyright &y& Elsevier]

• A summary of structural evolution and gas-phase reactivity of coinage metal clusters. • Advances in metal nanoclusters (NCs) with emphasis on catalysis and photochemistry. • The correlation between the NCs and corresponding naked metal clusters is emphasized. Building metal materials with well-defined components and the monomer-genetic property is one of the foremost challenges in chemistry and materials science. In recent years, metal nanoclusters especially those of coinage groups (i.e., Cu, Ag, and Au) have received reasonable research interest due to the availability of atomic-level precision via joint experimental and theoretical methods, enabling to unveil the mechanisms in diverse nano-catalysts and functional materials. A variety of ligand-protected metal nanoclusters (NCs) and solid-supported metal clusters have found high catalytic activity and unique selectivity in many catalytic reactions, shedding light on the size effect and active-sites mechanism, providing rational and quantitative information of surface charge state and metal-support interactions. Some ligand-protected metal NCs have been illustrated to exhibit superatom characteristics of the metallic core. This review aims to fully unveil the chemistry of coinage metal clusters. To begin with structural evolution and reactivity, we introduce the catalysis and photochemistry of coinage metal clusters from the point of view of charge-transfer redox and frontier orbitals, and bring forth a proposal to establish superatom chemistry and to connect cluster science and new materials of "cluster genes" as named cluster-genetic materials. [ABSTRACT FROM AUTHOR]

• Certain thirteen-atom metal clusters exhibit special stability in both gas and liquid phases. • The dual role of electronic and geometric structures governing the stability of superatoms. • Plenty nanoparticles can be considered as assemblies composing more than one thirteen-atom moieties. • Cluster assembly containing thirteen-atom core is proposed to be structural gene for modern materials. The stability of metal clusters is often associated with relatively low energy, highly symmetric structure, electronic shell closure and chemical reaction inertness, which is tunable by heteroatom doping or ligand protection. Gas-phase stable clusters of thirteen metal atoms, such as Al 13 −, are rationalized by superatom character with a likely closure of electron shell and/or geometric shell. On the other hand, a metallic core of 13 atoms is embodied in many ligand-protected nanoclusters (typically M 25 and M 55 , M = Au, Ag, Cu, etc.), also pertaining to superatomic stability. Here we summarize the advances of 13-atom metal clusters, endeavoring to fully convey the structural chemistry of metal clusters in gas-phase and their coordination chemistry in microscale condensed phase. We divide the reported studies into two main categories, i.e., naked 13-atom clusters in the gas phase and ligand-protected clusters with a 13-atom metal core, as well as those consisting of novel 13-atom moieties. Insights into such stable metal clusters enable to facilitate better understanding of fundamentals in condensed-phase chemistry and likely to use such 13-atom clusters as structural gene for modern materials. [ABSTRACT FROM AUTHOR]

Bulk cobalt does not react with water at room temperature, but cobalt nanometals could yield corrosion at ambient conditions. Insights into the cobalt cluster reactions with water and oxygen enable us to better understand the interface reactivity of such nanometals. Here we report a comprehensive study on the gas-phase reactions of Con±/0 clusters with water and oxygen. All these Con±/0 clusters were found to react with oxygen, but only anionic cobalt clusters give rise to water dissociation whereas the cationic and neutral ones are limited to water adsorption. We elucidate the influences of charge states, bonding modes and dehydrogenation mechanism of water on typical cobalt clusters. It is unveiled that the additional electron of anionic Con– clusters is not beneficial to H2O adsorption, but allows for thermodynamics- and kinetics-favourable H atom transfer and dehydrogenation reactions. Apart from the charge effect, size effect and spin effect play a subtle role in the reaction process. The synergy of multiple metal sites in Con– clusters reduces the energy barrier of the rate-limiting step enabling hydrogen release. This finding of water dissociation on cobalt clusters put forward new connotations on the activity series of metals, providing new insights into the corrosion mechanism of cobalt nanometals. Cobalt-based materials have a wide range of applications from information storage to electromagnetic absorbers in aerospace manufacturing, but the corrosion of cobalt nanosurfaces is poorly explored. Here, the authors combine mass spectrometry and DFT to study gas-phase reactions of Con±/0 (n = 1–30) with water and oxygen and find that only anionic cobalt clusters give rise to water dissociation, whereas the cationic and neutral ones are limited to water adsorption. [ABSTRACT FROM AUTHOR]

We report a joint experimental and theoretical study on the stability and reactivity of Bin+ (n=5–33) clusters. The alternating odd‐even effect on the reaction rates of Bin+ clusters with NO is observed, and Bi7+ finds the most inertness. First‐principles calculation results reveal that the lowest energy structures of Bi6‐9+ exhibit quasi‐spherical geometry pertaining to the jellium shell model; however, the Bin+ (n≥10) clusters adopt assembly structures. The prominent stability of Bi7+ is associated with its highly symmetric structure and superatomic states with a magic number of 34e closed shell. For the first time, we demonstrate that the unique s‐p nonhybrid feature in bismuth rationalizes the stability of Bi6‐9+ clusters within the jellium model, by filling the 6s electrons into the superatomic orbitals (forming "s‐band"). Interestingly, the stability of 18e "s‐band" coincides with the compact structure for Bin+ at n≤9 but assembly structures for n≥10, showing an accommodation of the s electrons to the geometric structure. The atomic p‐orbitals also allow to form superatomic orbitals at higher energy levels, contributing to the preferable structures of tridentate binding units. We illustrate the s‐p nonhybrid nature accommodates the structure and superatomic states of bismuth clusters. [ABSTRACT FROM AUTHOR]

Two series of cocrystals with the formula Ln(NO3)5·H2TPPZ (Ln = Eu, Tb, Er and Y, TPPZ = 2,3,5,6-tetra-2-pyridinylpyrazine) have been designed and synthesized. Utilizing single crystal structure parsing, we demonstrate how weak hydrogen bonding interactions between lanthanide nitrates and organic molecules stabilize their cocrystal structures. The lanthanide contraction effect is also proposed to help determine the Ln–O bond regularity, hence rationalizing the stability and structural variation of the cocrystals. Furthermore, the luminescence properties of these cocrystals were analyzed in detail. We found an interesting result of decent red fluorescence of the 1-Eu cocrystal complex. [ABSTRACT FROM AUTHOR]

Why one chemical is more stable than another is not always easy to understand. A unified answer for metal clusters has led to the establishment of the superatom concept, which rationalizes the delocalization of electrons; however, cluster stability based on superatom theory has not been confirmed unambiguously for any metal other than the s- and p-blocks of the periodic table of elements. Here, we have prepared pure niobium clusters and observed their reactions with CO under sufficient gas collision conditions. We find prominent inertness of Nb12+, which survives CO attack. Comprehensive theoretical calculation results reveal that the inertness of Nb12+ is associated with its cage structure and well-organized superatomic orbitals, giving rise to energetic superiority among the studied clusters. It is revealed that not only the 5s but also the 4d electrons of Nb delocalize in the cluster and significantly contribute to the superatomic state, resulting in reasonable cage aromaticity. This hollow-cage cluster, which we have called a 'niobespherene', provides a clue with regard to designing new materials of all-metal aromaticity and Nb-involved catalysts free of CO poisoning. [ABSTRACT FROM AUTHOR]

We report a joint experimental and theoretical study of the gas‐phase reactions between rhodium clusters Rhn+ (n=1–24) and small hydrocarbons. It is found that most Rhn+ clusters react with CH4 to form absorption products Rhn(CH4)1,2+ but Rh3+ reacts to form carbide indicative of complete dehydrogenation; Rh2+ reacts with CH4 to form partial dehydrogenation products Rh2CH2+ and Rh2C2H6+. The distinctive reactivity of Rh3+ is also found for the reactions with C2H2, C2H4 and C2H6, where the complete dehydrogenation product Rh3C2+ is also formed. Analysis of reaction kinetics demonstrates that the cooperation of three Rh atoms plays a key role in the dehydrogenation reaction. Notably, Rh3+ bears a large HOMO‐LUMO gap and reasonable stablity, and the roughly equal contribution of electrostatic and orbital interactions provide advantages to form two symmetric Rh−H−C hydrogen bridge bonds which promote the synergic cluster catalysis for hydrogen atom transfer and C−H bond dissociation. The efficient dehydrogenation mediated by an Rh3+ cluster opens a window to design new catalysts for C−H activation. [ABSTRACT FROM AUTHOR]

The reactions of Co n − clusters with acetylene find a magic species Co 12 C 12 − which exhibits a highly symmetric cage structure and unique chemical bonding. We name it as metallo-carbospherene and propose it as an ideal candidate for hydrogen storage materials. [Display omitted] [ABSTRACT FROM AUTHOR]

We have developed an integrated instrument system of a multiple-ion laminar flow tube (MIFT) reactor combined with a tandem quadrupole mass spectrometer (TQMS) and soft-landing deposition (SD) apparatus. A customized water-cooling magnetron sputtering (MagS) source is designed, by which we are able to attain a highly efficient preparation of metal clusters of 1–30 atoms with tunable size distributions. Following the MagS source, a laminar flow tube reactor is designed, allowing for sufficient gas–collision reactions of the as-prepared metal clusters, which is advantageous for probing magic clusters and minimizing wall effects when probing the reaction dynamics of such clusters. The customized TQMS analyzer involves a conical octupole, two linear octupoles, a quadruple ion deflector, and a 19 mm quadruple mass analyzer, allowing to decrease the pressure stepwise (from ∼5 to ∼10−9 Torr), thus ensuring high sensitivity and high resolution of the mass spectrometry analysis. In addition, we have designed a dual SD apparatus for the mass-selected deposition of clusters and their reaction products. For the whole system, abbreviated as MagS-MIFT-TQMS-SD, we have performed a detailed ions-fly simulation and quantitatively estimated the ions transfer efficiency under vacuum conditions determined by real experiments. Taking these advantages, well-resolved Pbn+, Agn+, and Nbn+ clusters have been produced, allowing for meticulous studies of cluster reactions under sufficient gas-phase collisions free of electric field trapping. Also, we have tested the efficiency of the dual SD. [ABSTRACT FROM AUTHOR]

Development of Raman spectroscopy, profiting from surface-enhanced Raman scattering and tip-enhanced Raman scattering techniques, has inspired extensive research interest for trace analysis and dynamic measurements up to single-molecule level. For another, Raman spectroscopy has also been recognized of significance in solving some important issues relating to molecule aggregates in chemistry and biology, owing to the capability of non-destructive detection and high-resolution fingerprints by which molecules and their aggregates can be identified. Herein, we summarize the recent progress of Raman spectroscopy in probing single molecules and molecular aggregates and block out a future prospective of Raman spectroscopy applied in cluster science. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The study of clusters with strongly size-dependent properties has attracted extensive attention due to their potential applications in building new materials. Utilizing a home-made multiple-ion laminar flow tube reactor in tandem with a customized triple quadrupole mass spectrometer, we have studied the reactions of niobium cationic clusters with acetylene and ethylene. It is observed that dehydrogenation dominates the reaction process, and Nb4C4+ shows up prominently in the mass spectra. Quantum chemistry calculations reveal that the most stable structure of Nb4C4+ corresponds to a slightly distorted cubic structure with D2d symmetry, with reasonable stability pertaining to its cubic aromaticity. We illustrate the dehydrogenation reaction paths of Nb4+ + 2C2H2 to form the prominent Nb4C4+ product, along with the highly exothermic reactions to produce H2. [ABSTRACT FROM AUTHOR]

Exploring stable clusters to understand structural evolution from atoms to macroscopic matter and to construct new materials is interesting yet challenging in chemistry. Utilizing our newly developed deep-ultraviolet laser ionization mass spectrometry technique, here we observe the reactions of neutral cobalt clusters with oxygen and find a very stable cluster species of Co13O8 that dominates the mass distribution in the presence of a large flow rate of oxygen gas. The results of global-minimum structural search reveal a unique cubic structure and distinctive stability of the neutral Co13O8 cluster that forms a new class of metal oxides that we named as 'metalloxocubes'. Thermodynamics and kinetics calculations illustrate the structural evolution from icosahedral Co13 to the metalloxocube Co13O8 with decreased energy, enhanced stability and aromaticity. This class of neutral oxygen-passivated metal clusters may be an ideal candidate for genetic materials because of the cubic nature of the building blocks and the stability due to cubic aromaticity. [ABSTRACT FROM AUTHOR]

We report the single‐crystal synthesis of a chlorine‐centered bimetallic cluster, Cl@Ag22Au6(4‐TBBT)28(PPh4), which bears a quatrefoil‐structured Cl@Ag22(SR)16 core studded by six Au(SR)2 staples showing a quasi Td symmetry. This cluster bears 28 metal atoms and 28 ligands, with a chlorine atom hosted in the center of the metallic Ag22Au6 core. Single‐crystal analysis shows that this cluster possesses essentially a different bonding nature compared with other monolayer‐protected metal clusters (MPCs) or traditional metal‐sulfur complexes. We fully dissect the structure evolution in forming such a chlorine‐centered cluster. Interestingly, this cluster, Cl@Ag22Au6(4‐TBBT)28(PPh4), displays a fluorescence emission at 570 nm and supports the solid emission with a minor red shift at 574 nm. On the other hand, we have tested the nonlinear optical property and observed unambiguous nonlinear optical property with a normal valley‐shaped transmittance curve corresponding to reverse saturated absorption (RSA) of the cluster. [ABSTRACT FROM AUTHOR]

We have synthesized Ag7 nanoclusters via a facile one‐pot procedure with p‐aminothiophenol (PATP) as the ligand. The chemical component of this Ag7 cluster is determined to be Ag7(C6H6NS)7H+ by high‐resolution electrospray mass spectrometry, where a few fragment peaks are also observed such as [Ag7(C6H6NS)4H3Na]+. For this PATP‐protected Ag7 cluster, we have conducted a Raman investigation to probe in the intracluster interactions and find an essentially different Raman feature from that the nascent PATP ligand, pertaining to photo‐assistant catalytic conversion of PATP to p,p'‐dimercapto azobenzene (DMAB). Utilizing density‐functional‐theory (DFT) calculations, we have performed natural population analysis, natural bond orbital analysis, and electron density difference analysis to fully demonstrate the intracluster interactions between Ag7 clusters and the ligand. What is interesting is that the protection ligand PATP helps stabilize the Ag7 metallic core, and in turn, the metal core Ag7 catalyzes the protection ligands giving rise to N─N coupling reaction. On this basis, we have proposed a reaction pathway on a basis of DFT calculations to provide further insights into the reaction mechanism of PATP‐to‐DMAB conversion at the presence of the Ag7 clusters. [ABSTRACT FROM AUTHOR]

The interaction of pyridine–Ag has been a hot topic since the finding of surface‐enhanced Raman scattering; however, there is still challenge to accurately evaluate the interactions within nano‐systems. Here we have synthesized chemically pure Ag18 nanoclusters by a facile method based on laser ablation in liquid and conducted a joint experimental and theoretical Raman spectroscopic study for pyridine adsorbed on the specific‐sized Ag clusters. As a result, altered Raman feature for the pyridine‐Ag18 system in contrast to pure pyridine is observed shedding light on the charge‐transfer interactions between pyridine and Ag. Utilizing natural population analysis, we studied the charge distribution before and after pyridine adsorbed on the Ag18 cluster. Also, we calculated static polarizability components and isotropic polarizability of pyridine and the pyridine‐Ag18 complex and studied the donor‐acceptor orbital overlaps via natural bond orbital analysis, charge decomposition analysis, electron density difference analysis, and density of state analysis. Such a comprehensive and semiquantitative study provides firm evidence for the chemical mechanism in surface‐enhanced Raman scattering theory. [ABSTRACT FROM AUTHOR]

As a monoamine neurotransmitter, serotonin affects a wide range of physiological and behavioral procedures of humans but its biological function is complex and multifaceted. Here we present a comprehensive study of the weak serotonin‐residue interactions from cluster science point of view. Eight pairs of serotonin‐residue binary clusters are representatively studied. Upon the most stable structures we depict the hydrogen bonding interaction patterns, along with natural bond orbital (NBO) analysis, atoms in molecules (AIM) analysis, generalized Kohn‐Sham energy decomposition analysis (GKS‐EDA), as well as noncovalent interaction plots based on independent gradient model (IGM). It is found that, for nitrogenous residues, the N⋅⋅⋅H−O dominates the noncovalent interactions; while for hydroxyl‐containing residues, O−H⋅⋅⋅N takes over the dominant interactions; for oxygen and nitrogen‐free residues, both electrostatic and VDW‐like H‐bonds stabilize the binary clusters. This information enriches the molecular mechanism of serotonin receptors and paves a way to study the weak interactions of physiological‐active molecules and also supramolecular materials. [ABSTRACT FROM AUTHOR]

We have developed an integrated instrument combining deep ultraviolet laser ionization mass spectrometry (DUV-LIMS) and infrared multiphoton dissociation (IR-MPD) spectroscopy, abbreviated as DUV-IR. The 177.3 nm DUV laser (7 eV single-photon energy) has short pulse duration (15 ps) and appropriate pulse energy (∼20 µJ), which is found to be highly efficient for low-fragment photoionization of neutral metal clusters and molecules. A home-made cluster source is designed with an adjustable formation channel suitable for the generation of different cluster series. The well-aligned components of the reflection time-of-flight mass spectrometer, as well as the coaxial design of DUV laser and molecular beam, bring forth high sensitivity and high resolution of the DUV-LIMS. Taking these advantages, well-resolved neutral Vn (n = 1–43) and (Benzene)n (n = 1–25) clusters have been generated free of fragmentation. In addition to the generation and detection of neutral clusters, a fast-flow reaction tube is also designed downstream of the cluster source allowing to study their reactivity. In particular, a broad-range tunable IR laser (1.3–16 µm) is coupled with the DUV laser to attain IR-MPD spectroscopic analysis. This integrated system offers a general protocol to prepare various clusters to study their gas-phase reactivity and to determine their structures. [ABSTRACT FROM AUTHOR]

We report here a photodissociation study of tyramine, tryptamine and histamine using the customized time‐of‐flight mass spectrometer (TOF‐MS) combined deep ultraviolet laser ionization. The cleavage of Cα‐Cβ bond, free of hydrogen atom transfer (HAT), is observed under the 177 nm DUV laser excitation, which is different from the HAT‐involved photodissociation by a 118 nm vacuum ultraviolet (VUV) laser. With aid of density function theory (DFT) calculations, we demonstrate the photochemical reaction mechanism of these neurotransmitter molecules with dependence on residual energies after photoionization and donor‐acceptor orbital interactions. This finding helps to enrich the understanding of structure chemistry of neurotransmitters. In particular, the brittle fracture of Cα‐Cβ bond initiated by the ultrafast DUV laser could stimulate research interest in designed synthesis of organic compounds. [ABSTRACT FROM AUTHOR]

Utilizing a customized mass spectrometer, we analyze selective C–C bond and C–N bond activation in neurotransmitters dopamine (DA) and norepinephrine (NE) under deep ultraviolet laser irradiation. [ABSTRACT FROM AUTHOR]

Hydrogen atom transfer (HAT) and bond dissociation of amino acids are studied utilizing a customized vacuum ultraviolet laser ionization mass spectrometer (VUV‐LIMS). Three typical molecules (glycine, threonine and cysteine) which have similar structures but a minor difference by having one or two bonds associated with Cα or having a sulfhydryl were select in this study. As results, glycine finds a simplex dissociation pathway by producing CNH4+ (m/z 30) indicative of direct bond cleavage of Cα‐C1 (C1 stands for the carbon atom of the carboxyl group here). Threonine bears two bonds associated with Cα and they both dissociate under VUV excitation, giving rise to three major mass peaks at m/z 30 (CNH4+), 44 and 75 respectively along with selective HAT process. Interestingly, cysteine also bears two dissociative bonds associated with Cα, however, the dominant HAT for producing NH3, CNH4+ or CO2 was found to be dramatically restrained by the production of H2S which is known as an important gasotransmitter in biological nervous system. Based on density functional theory (DFT) calculations, an in‐depth analysis is conducted to show the thermodynamics and reaction kinetics in forming these fragments with or without a HAT process. It is demonstrated that the HAT‐accommodated structure relaxation and incidental elongation of the bonds associated with Cα, depending on the residual energies after ionization, bring forth competitive and cooperative effect in determining the selectivity of alpha‐beta carbon chemistry. Photoexcitation and diverse photodissociation of amino acids are studied utilizing the customized vacuum ultraviolet laser ionization mass spectrometer. We rationalize the HAT‐involved structure relaxation and incidental cleavage of Cα‐linked bonds, and unravel the competitive and cooperative effect in determining the selectivity of alpha carbon chemistry. [ABSTRACT FROM AUTHOR]

We have synthesized gold/silver nanoclusters (NCs) under the protection of both bovine-serum-albumin (BSA) and lysozyme (Lyz) and found that the NCs protected by the mixed-proteins give rise to largely enhanced stability and fluorescence, enabling promising applications for chemosensing and bioimaging. The enhanced fluorescence of Au NCs was found to be exclusively quenched at the presence of Hg 2+ ions with an ultralow detection limit up to ∼0.7 nM. It is also interesting to find that the BSA-Lyz-Au NCs are nontoxic and available for fluorescence imaging of Hg 2+ detection in MCF-7 cells. The low cytotoxicity, good penetrability and fluorescence sensitivity of BSA-Lyz-Au NCs suggest promising biological applications. Similar observations were also addressed for the Ag system, indicating general applicability of this facile strategy based on BSA-Lyz mixed proteins for the protection of metal NCs. [ABSTRACT FROM AUTHOR]

Employing glutathione (HSG) as a protecting ligand, we have synthesized water-soluble and biocompatible Ag 14 (SG) 12 nanoclusters (Ag 14 NCs) of which the composition and structure are determined via high-resolution mass spectrometry, fingerprint spectroscopy and DFT calculations. Natural bond orbital (NBO) analysis on a basis of first-principles theoretical calculations demonstrates the donor–acceptor orbital overlaps and charge-transfer interactions between silver and the ligand HSG. Further, it is interestingly found that the fluorescence of Ag 14 NCs can be largely enhanced at the presence of lysozyme distinguishing from other proteases which we have tested, revealing the feasibility of Ag 14 NCs as chemosensing to identify lysozyme. Also found is that, the fluorescence on-state of the obtained Ag 14 NCs-Lys can be exclusively switched off at the addition of Hg 2+ ions with an ultralow detection limit of ∼16.2 nM. This interesting finding reveals Ag 14 NCs a versatile chemosensor to identify lysozyme from proteases and to detect mercury ions from various cations. [ABSTRACT FROM AUTHOR]

Here we report a successful synthesis of water-soluble 13-atoms gold clusters under the monolayer protection of binary thiolates, glutathione and penicillamine, under a molecular formula of Au 13 (SG) 5 (PA) 7 . This monolayer-protected cluster (MPC) finds decent stability and is demonstrated to possess an icosahedral geometry pertaining to structural accommodation in contrast to a planar bare Au 13 of local minima energy. Natural bond orbital (NBO) analysis depicts the interaction patterns between gold and the ligands, enlightening to understand the origin of enhanced stability of the Au 13 MPCs. Further, the water-soluble Au 13 MPCs are found to be a decent candidate for chemosensing and bioimaging. [ABSTRACT FROM AUTHOR]

A photoelectron velocity-map imaging (VMI) apparatus has been developed from the DUV-IR photoionization mass spectrometry and spectroscopy instrument. A 45-degree plate-set is designed and combined with the upright reflection time-of-flight mass spectrometer (Re-TOFMS) to pick up target cluster anions and change their trajectory after the vertical reflection. Following the ion-extraction zone, the mass-selected cluster anions then pass through up-down and left-right trajectory adjustment and beam focus until the arrival at the photoelectron detachment zone to encounter the normal incidence of a pulsed UV laser. The detached electrons are subject to acceleration and detected by a dual micro-channel plate detector and imaging on the phosphor screen. This 45-degree ion-extraction photoelectron VMI setup not only expands the function of our DUV-IR instrument for structural chemistry but also facilitates the compatibility with the conventional upright reflection of TOFMS. [Display omitted] [ABSTRACT FROM AUTHOR]

We report here the development of a reflectron time-of-flight mass spectrometer utilizing singlephoton ionization based on an all-solid-state deep ultraviolet (DUV) laser system. The DUV laser was achieved from the second harmonic generation using a novel nonlinear optical crystal KBe2BO3F2 under the condition of high-purity N2 purging. The unique property of this laser system (177.3-nm wavelength, 15.5-ps pulse duration, and small pulse energy at ~15 μJ) bears a transient low power density but a high single-photon energy up to 7 eV, allowing for ionization of chemicals, especially organic compounds free of fragmentation. Taking this advantage, we have designed both pulsed nanospray and thermal evaporation sources to form supersonic expansion molecular beams for DUV single-photon ionization mass spectrometry (DUV-SPI-MS). Several aromatic amine compounds have been tested revealing the fragmentation-free performance of the DUV-SPI-MS instrument, enabling applications to identify chemicals from an unknown mixture. [ABSTRACT FROM AUTHOR]

[Display omitted] • We present an insight of C-C bond formation in the coupling of methanol by Ti clusters. • Ti 13 exhibits relatively higher binding energy compared to Ti 7 and Ti 15. • We have synthesized Ti 13 clusters by laser ablation in methanol, and studied the catalysis for methanol coupling reactions. • The observation of dominant mass peak of (CH 3 O) 2 K± concurs with the calculated reaction pathways. Alcohol coupling, also known as the Guerbet reaction, is a potentially important process to increase the value of short chain hydrocarbons. We present here an insight of C-C bond formation in the coupling of methanol to higher alcohols by Ti clusters. We have synthesized Ti 13 clusters by laser ablation in methanol, and studied the catalysis for methanol coupling reactions using high resolution mass spectroscopy and also density-functional theory calculations. The experimental findings concurs with the calculated kinetic- and thermodynamic- allowed reaction pathways, helping to understand the catalytic mechanism of alcohols conversion chemistry on the transition metal catalysts. [ABSTRACT FROM AUTHOR]

Water and its interactions with metals are closely bound up with human life, and the reactivity of metal clusters with water is of fundamental importance for the understanding of hydrogen generation. Here a prominent hydrogen evolution reaction (HER) of single water molecule on vanadium clusters Vn+ (3 ≤ n ≤ 30) is observed in the reaction of cationic vanadium clusters with water at room temperature. The combined experimental and theoretical studies reveal that the wagging vibrations of a V-OH group give rise to readily formed V-O-V intermediate states on Vn+ (n ≥ 3) clusters and allow the terminal hydrogen to interact with an adsorbed hydrogen atom, enabling hydrogen release. The presence of three metal atoms reduces the energy barrier of the rate-determining step, giving rise to an effective production of hydrogen from single water molecules. This mechanism differs from dissociative chemisorption of multiple water molecules on aluminium cluster anions, which usually proceeds by dissociative chemisorption of at least two water molecules at multiple surface sites followed by a recombination of the adsorbed hydrogen atoms. Metal clusters are known to catalyze hydrogen evolution from water, but reaction mechanisms and reactivities are still not fully understood. Here, mass spectrometry of cationic vanadium clusters reacting with water vapor shows significant hydrogen evolution reactions for V3+, V5+ and V9+ that point to a hydrogen release mechanism from the transition metal cluster cations. [ABSTRACT FROM AUTHOR]