Ultrasmall Cluster Model for Investigating Single Atom Catalysis: Dehydrogenation of 1-Propanamine by Size-Selected PtZrO Clusters Supported on HOPG.

The selective dehydrogenation of hydrocarbons and their functionalized derivatives is a promising pathway in the realization of endothermic fuel systems for powering important technologies such as hypersonic aircraft. The recent surge in interest in single atom catalysts (SACs) over the past decade offers the opportunity to achieve the ultimate levels of selectivity through the subnanoscale design tailoring of novel catalysts. Experimental techniques capable of investigating the fundamental nature of the active sites of novel SACs in well-controlled model studies offer the chance to reveal promising insights.

A magnetic bottle time-of-flight electron spectrometer suitable for continuous ionization sources.

We present a newly developed magnetic-bottle time-of-flight electron spectrometer suitable for continuous or quasicontinuous photoionization sources such as synchrotrons. A strong magnetic field collects almost all photoelectrons from a well-defined ionization volume and quantitatively suppresses background electrons which originate outside of this interaction region. Although it is a pulsed instrument, a relatively high duty cycle is achieved by storing the photoelectrons generated between two cycles in an electromagnetic trap.

On the linewidth in photoelectron spectra of size-selected clusters.

A systematic analysis of the average linewidth of features in the photoelectron spectra of size-selected elemental clusters consisting of up to 10 atoms is presented. With increasing atomic weight, the average linewidth decreases. Several possible reasons for this trend are discussed.

Long-lived excited states in metal clusters.

Bare metal clusters have properties that make them interesting for applications in photochemistry and photovoltaics. Long-lived excited states are a prerequisite for such applications, because in them the energy of the photon can be stored. Clusters have a low density of states and long-lived excited states should therefore occur frequently.

Photoelectron spectroscopy of boron aluminum hydride cluster anions.

Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, BxAlyHz(-), were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer.

Size-selected gold clusters on porous titania as the most "gold-efficient" heterogeneous catalysts.

Research on homogeneous and heterogeneous catalysis is indeed convergent and finds subnanometric particles to be at the heart of catalytically active species. Here, monodisperse gold clusters are deposited from the gas phase onto porous titania generating well-defined model systems and the resulting composite materials exhibit a sharp size-dependency on the number of gold atoms per cluster and exceptionally high-turnovers toward the bromination of 1,4-dimethoxybenzene are observed. This indicates that the deliberate generation of active centres is of utmost importance for the creation of the most "gold-efficient" catalysts.

The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters.

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of MgmAln (-) (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer.

Communication: In search of four-atom chiral metal clusters.

A combined study utilizing anion photoelectron spectroscopy and density functional theory was conducted to search for four-atom, chiral, metal, and mostly metal clusters. The clusters considered were AuCoMnBi(-/0), AlAuMnO(-/0), AgMnOAl(-/0), and AuAlPtAg(-/0), where the superscripts, (-/0), refer to anionic and neutral cluster species, respectively. Based on the agreement of experimentally and theoretically determined values of both electron affinities and vertical detachment energies, the calculated cluster geometries were validated and examined for chirality.

On the existence of designer magnetic superatoms.

The quantum states in small, compact metal clusters are bunched into electronic shells with electronic orbitals resembling those in atoms, enabling classification of stable clusters as superatoms. The filling of superatomic orbitals, however, does not generally follow Hund's rule, and it has been proposed that magnetic superatoms can be stabilized by doping simple metal clusters with magnetic atoms. Here, we present evidence of the existence of a magnetic superatom and the determination of its spin moment.

(PbS)32: a baby crystal.

Theoretical calculations based on density functional theory have found (PbS)(32) to be the smallest cubic cluster for which its inner (PbS)(4) core enjoys bulk-like coordination. Cubic (PbS)(32) is thus a "baby crystal," i.e.

Communications: Chain and double-ring polymeric structures: Observation of Al(n)H(3n+1) (-) (n=4-8) and Al(4)H(14) (-).

A pulsed arc discharge source was used to prepare gas-phase, aluminum hydride cluster anions, Al(n)H(m) (-), exhibiting enhanced hydrogen content. The maximum number of hydrogen atoms in Al(n)H(m) (-) species was m=3n+1 for n=5-8, i.e.

Reactivity of aluminum cluster anions with ammonia: selective etching of Al11(-) and Al12(-).

Reactivity of aluminum cluster anions toward ammonia was studied via mass spectrometry. Highly selective etching of Al(11)(-) and Al(12)(-) was observed at low concentrations of ammonia. However, at sufficiently high concentrations of ammonia, all other sizes of aluminum cluster anions, except for Al(13)(-), were also observed to deplete.