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 py rolitic graphite and naturally oxidized Si(111) surfaces have been stu died by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelect ron spectroscopy (WS) (HeI) and metastable impact electron spectroscop y (MIES). Strong emission from the ionization of the molecular orbital s of the carboxyl (COOH) functional group is identified in the MIES an d UPS spectra of the Mm-micelle on both substrates. The results sugges t that the outermost functional group of the MTP-micelle is the carbox yl group, and that the Au MTPs are covered with propionic-acid-thiolat es. 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 t he silica substrate the alpha-(root 3 x root 3)R30 degrees-Au structur e is observed with low energy electron diffraction after annealing to 1000 degrees C. (C) 1998 Elsevier Science B.V. All rights reserved.