Characterization of aluminum–organic-stabilized platinum–colloid networks with electron and photon spectroscopies

We have measured and interpreted the ultraviolet (HeI) and X-ray photoelectron spectra and the metastable impact electron spectra (MIES) from aluminum–organic-stabilized platinum–colloids and colloid networks, deposited on silicon substrates and characterized by X-ray photoelectron spectroscopy, scanning Auger electron microscopy and transmission electron microscopy. MIES, in particular, gives information on the electronic structure of the spacer molecules interconnecting the colloids. In addition, changes in the electronic structure of the platinum clusters that are induced by different spacer molecules were identified by means of X-ray absorption near-edge structure measurements at the platinum LIII-edge of these materials. This combination of techniques was also employed to follow the chemical changes that occur upon heating of the network in situ. It turns out that the thermal decomposition of the network is driven by the disintegration of the spacer molecules. Moreover, less sintering of the colloidal particles occurs in the networked systems than in unconnected particles. Most of the networked platinum–particles are still present in their original shape even after the destruction of spacer molecules. This observation could be linked to the encapsulation of these platinum particles into an (AlO) protecting shell. Copyright © 2003 John Wiley & Sons, Ltd.