We present X-ray absorption spectroscopy (XAS) data, ultraviolet photoelectron spectra (HeI) and metastable impact electron spectra (MIES) of cobalt nanoparticles (typically 4 to 10 nm), prepared by Co 2 (CO) 8 thermolysis and pre-stabilized by smooth oxidation. We find that the particles consist of a core-shell system with a dominantly f.c.c. core and a shell in which Co-C and Co-O coordination is likely to occur. This corresponds well to the results from electron spectroscopy, that stabilization occurs via formation of (Co-CO x ) and (Co-O) groups formed during the oxidation procedure and appears sensitive to the reaction conditions. Peptization of the pre-stabilized particles with KorantinSH surrounds the particles with a dense organic shell, stable up to about 250 • C. The carbonic acid molecules of the shell are oriented predominantly perpendicular to the surface of the particles, their carboxyl functional group linking the shell with the cobalt particles. This result is also supported by the XAS data, where it is observed that, during peptization, Co-C coordination is partly replaced by Co-O coordination. In order to arrive at these statements, auxiliary measurements on bare and gas-exposed cobalt films, also reported here, were required.

Metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS(HeI)) and x-ray photoelectron spectroscopy (XPS) were applied to study the interaction of O 2 , CO and CO 2 with Co films at room temperature. The films were produced on Si(100) surfaces under the in situ control of MIES, UPS and scanning tunnelling microscopy (STM). For O 2 , dissociative adsorption takes place initially and then incorporation of oxygen starts at exposures of ∼5 L. Comparison of the MIES and UPS spectra with those published for CoO shows that near-stoichiometric CoO films can be obtained by co-deposition of Co and O 2 . The CO is adsorbed molecularly up to a maximum coverage of ∼0.6 monolayer, with the C-end pointing towards the surface. The CO 2 adsorption is dissociative, resulting in the formation of Co-CO bonds at the surface. The resulting oxygen atoms are mostly incorporated into the Co layer. For all studied molecules the interaction with Co is similar to that with Ni.

Nanoparticle networks can be synthesized by the self‐assembly of arrays of metal colloid particles linked by spacer molecules of different sizes. The particles are linked through reactive aluminum sites in a metal–organic shell around the metal particles. Rigid spacer molecules with functional groups at each end are used to bind at these reactive sites. The resulting networks have been characterized by various methods such as transmission electron microscopy (TEM), sorption analysis, X‐ray absorption spectroscopy (XAFS), anomalous small angle X‐ray scattering (ASAXS), metastable impact electron spectroscopy (MIES), and ultraviolet photoelectron spectroscopy (UPS). These investigations showed that the metal nanoparticles form aggregated networks with average distances between the metal particles that are determined by the sizes of the spacer molecules applied. In this way, porous as well as nonporous networks have been obtained. Whether accessible pores are formed depends on the type of spacer molecule. Furthermore, the properties of the metal particles have proved to be sensitive towards the reaction of the aluminum in the protective shells with the linker molecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)