title: Molecular Adsorption Changes the Quantum Structure of Oxide-Supported Gold Nanoparticles: Chemisorption versus Physisorption.
abstract: STM conductance spectroscopy and mapping has been used to analyze the impact of molecular adsorption on the quantized electronic structure of individual metal nanoparticles. For this purpose, isophorone and CO2, as prototype molecules for physisorptive and chemisorptive binding, were dosed onto monolayer Au islands grown on MgO thin films. The molecules attach exclusively to the metal-oxide boundary, while the interior of the islands remains pristine. The Au quantum well states are perturbed due to the adsorption process and increase their mutual energy spacing in the CO2 case but move together in isophorone-covered islands. The shifts disclose the nature of the molecule-Au interaction, which relies on electron exchange for the CO2 ligands but on dispersive forces for the organic species. Our experiments reveal how molecular adsorption affects individual quantum systems, a topic of utmost relevance for heterogeneous catalysis.
authors.affiliation: Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Stiehler
authors.affiliation: Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany.
authors.forename: Florencia
authors.initials: F
authors.lastname: Calaza
authors.affiliation: Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany.|Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Wolf-Dieter
authors.initials: WD
authors.lastname: Schneider
authors.affiliation: Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany.|Carl von Ossietzky Universität, 26111 Oldenburg, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Nilius
authors.affiliation: Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Freund