Study of Au multiple-twinned particle micelles by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (HeI) and metastable impact electron spectroscopy

Multiple-twinned particle (MTP) micelles, comprised of Au MTP and self-assembled propionic-acid-thiolates, deposited onto highly oriented pyrolitic graphite and naturally oxidized Si(111) surfaces have been studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (WS) (HeI) and metastable impact electron spectroscopy (MIES). Strong emission from the ionization of the molecular orbitals of the carboxyl (COOH) functional group is identified in the MIES and UPS spectra of the Mm-micelle on both substrates. The results suggest that the outermost functional group of the MTP-micelle is the carboxyl group, and that the Au MTPs are covered with propionic-acid-thiolates. By joint application of XPS, UPS (HeI) and MIES it is demonstrated that the thiolates desorb completely From the substrate (when heating to similar to 400 degrees C) while Au remains there. In the case of the silica substrate the alpha-(root 3 x root 3)R30 degrees-Au structure is observed with low energy electron diffraction after annealing to 1000 degrees C. (C) 1998 Elsevier Science B.V. All rights reserved.