The interaction of CO with structurally well-defined PdAg/Pd(111) surface alloys was investigated by temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) to unravel and understand contributions from electronic strain, electronic ligand and geometric ensemble effects. TPD measurements indicate that CO adsorption is not possible on the Ag sites of the surface alloys (at 120 K) and that the CO binding strength on Pd sites decreases significantly with increasing Ag concentration. Comparison with previous scanning tunneling microscopy (STM) data on the distribution of Pd and Ag atoms in the surface alloy shows that this modification is mainly due to geometric ensemble effects, since Pd(3) ensembles, which are the preferred ensembles for CO adsorption on non-modified Pd(111), are no longer available on Ag-rich surfaces. Consequently, the preferred CO adsorption site changes with increasing Ag content from a Pd(3) trimer via a Pd(2) dimer to a Pd monomer, going along with a successive weakening of CO adsorption. Additionally, the CO adsorption properties of the surface alloys are also influenced by electronic ligand and strain effects, but on a lower scale. The results are discussed in comparison with previous findings on PdAg bulk alloys, supported PdAg catalysts and PdAu/Pd(111) model systems.

Within the last years, a fundamental understanding of nanoscaled materials has become a tremendous challenge for any technical applications. For magnetic nanoparticles, the research is stimulated by the effort to overcome the superparamagnetic limit in magnetic storage devices. The physical properties of small particles and clusters in the gas phase, which are considered as possible building blocks for magnetic storage devices, are usually sizedependent and clearly differ from both the atom and bulk material. For any technical applications, however, the clusters must be deposited on surfaces or embedded in matrices. The contact to the environment again changes their properties significantly. Here, we will mainly focus on the fundamental electronic and magnetic properties of metal clusters deposited on surfaces and in matrices. This, of course, requires a well-defined control on the production of nanoparticles including knowledge about their structural behaviour on surfaces that is directly related to their www.elsevier.com/locate/surfrep Surface Science Reports 56 (2005) 189-275 $ This work is based on results of the EU ''AMMARE'' project within the Fifth Framework programme coordinated by Antonis N. Andriotis, Heraklion, Greece.

Depositing pre-formed gas-phase nanoparticles, whose properties can be widely varied, onto surfaces enables the production of films with designed properties. The films can be nanoporous or, if co-deposited with an atomic vapour, granular, allowing independent control over the size and volume fraction of the grains. This high degree of control over the nanostructure of the film enables the production of thin films with a wide variety of behaviour, and the technique is destined to make a significant contribution to the production of high-performance magnetic materials. Here we review the behaviour of magnetic nanoparticle assemblies on surfaces and in non-magnetic and magnetic matrices deposited from the gas phase at densities from the dilute limit to pure nanoparticle films with no matrix. At sufficiently low volume fractions (∼1%), and temperatures well above their blocking temperature, nanoparticle assemblies in non-magnetic matrices show ideal superparamagnetism. At temperatures below the blocking temperature, the magnetization behaviour of both Fe and Co particles is consistent with a uniaxial intra-particle magnetic anisotropy and an anisotropy constant several times higher than the bulk magnetocrystalline value. At relatively low volume fractions (≥5%) the effect of inter-particle interactions becomes evident, and the magnetization behaviour becomes characteristic of agglomerates of nanoparticles exchange coupled to form magnetic grains larger than a single particle that interact with each other via dipolar forces. The evolution of the magnetic behaviour with volume fraction is predicted by a Monte-Carlo model that includes exchange and dipolar couplings. Above the percolation threshold the films become magnetically softer, and films of pure clusters have a magnetic ground state that obeys the predicted magnetization behaviour of a correlated super-spin glass characteristic of random anisotropy materials. Magnetic nanoparticles in non-magnetic matrices show giant magnetoresistance behaviour, and the magnetotransport in deposited nanoparticle films is reviewed. Assembling Fe nanoparticles in Co matrices and vice versa is a promising technique for producing magnetic materials with a saturation magnetization that exceeds the Slater–Pauling limit. Structural studies reveal that the particles' atomic structure is dependent on the matrix material, and it is possible to prepare Fe nanoparticles with an fcc structure and, unusually, Co particles with a bcc structure. We also look to the future and discuss applications for materials made from more complex bi-metallic and core–shell nanoparticles.

Inorganic chemistry Z 0100Magnetic and Structural Properties of Isolated and Assembled Clusters -[227 refs.]. -(BANSMANN, J.; BAKER, S. H.; BINNS, C.; BLACKMAN, J. A.; BUCHER, J.-P.; DORANTES-DAVILA, J.; DUPUIS, V.; FAVRE, L.; KECHRAKOS, D.; KLEIBERT, A.; et al.; Surf. Sci. Rep. 56 (2005) 6-7, 189-275; Inst. Phys., Univ. Rostock, D-18051 Rostock, Germany; Eng.) -Schramke 52-215

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The ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMP][TFSA] is a promising candidate for improved nextgeneration rechargeable lithium−ion batteries. We here report results of a model study of the reactive interaction of (sub-)monolayers and multilayers of [BMP][TFSA] with lithium (Li) on Cu(111), employing scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIRS) under ultrahigh vacuum (UHV) conditions. Upon post-deposition of Li on [BMP][TFSA] multilayers at 80 K, we identified changes in the chemical state of the [TFSA] anion and the [BMP] cation as well as in the IR absorption bands related to the anion. These changes are most likely due to the decomposition of the IL adlayer into a variety of products like LiF, Li 2 S, and Li 2 O upon anion decomposition and LiN 3 , LiC x H y N, and Li x CH y upon cation decomposition, where the latter includes cracking of the pyrrolidinium ring. Deposition of Li on [BMP][TFSA] (sub-)monolayer-covered surfaces led to similar decomposition patterns, and the same was also observed for the reverse deposition order. The addition of the corresponding amounts of Li to a [BMP][TFSA] adlayer resulted in distinct changes in the STM images, which must be due to the surface reaction. After annealing to 300 K, the core-level peaks of the cation lose most of their peak area. Upon further heating to 450 K, the anion is nearly completely decomposed, resulting in LiF and Li 2 S decomposition products that dominate the interface.

Operando XAS measurements in the near (XANES) and the extended (EXAFS) Au L III edge as well as in situ diffuse reflectance FTIR (DRIFTS) spectroscopy were employed in combination with kinetic measurements in a further attempt to identify the nature of the active Au species responsible for the high activity of Au/CeO 2 catalyst in the lowtemperature water gas shift (LT-WGS) reaction. The changes in the reaction behavior during the LT-WGS were followed at 180 °C for different initial states of the catalyst, prepared by either reducing or oxidizing pretreatments at different temperatures. Findings from kinetic and deactivation measurements were correlated with experimental data on the Au particle size, the Au oxidation state, and the CO-Au adsorption properties directly after different pretreatments and during the subsequent LT-WGS reaction obtained by operando/in situ spectroscopy measurements. The combined experimental results show that the use of different pretreatments can significantly influence the electronic state of the Au species (Au δ-, Au 0 , Au δ+ ). Exposure to the reaction atmosphere under the present reaction conditions, however, results in the rapid formation of extremely small, (sub)nanometer-sized Au 0 nanoparticles, which are the dominant Au species and responsible for the high WGS activity. Small amounts of oxidic gold species (Au 3+ ) persisting during reaction after the strongly oxidative O400 pretreatment, in the few percent range, are too little to be responsible for the catalytic activity of that catalyst and changes therein with time on stream.