Chemical states of dodecanethiolate-passivated Au nanoparticles: synchrotron-radiation photoelectron spectroscopy

Abstract

We have carried out a photoemission study using synchrotron radiation of dodecanethiolate-(DT-) passivated Au nanoparticles supported on the highly oriented pyrolytic graphite (HOPG) substrates. From detailed line-shape analyses of Au 4f core-level photoemission spectra of DT-passivated Au nanoparticles, it is found that Au 4f core-level spectra consist of the two components. We attribute these components to the inner Au atoms and surface Au atoms bonded to surface dodecanethiolates. From these results, we discuss the chemical states of the present DT-passivated Au nanoparticles.

An insight into the optical properties of a sub nanosize glutathione stabilized gold cluster

“…S5) Based on the 4f 7/2 peak, Negishi et al and Tanaka and co workers have explained the mechanism of photoemission by de-convoluting the 4f 7/2 peak in the binding energy spectrum of gold. 4,28,29 The peak shift has been explained based on the 'initial state effect' due to electronic transition from gold core to thiolates, which applies to the observed shift in the present study also. 4 Slightly higher chemical shift observed for self assembled structures (AuC1, AuC2 and AuC4) is attributed to the electronic transition from self assembled electron to gold core/ surface gold atoms.…”

Final state effect for Au 4f line from gold-nano-particles grown on oxides and HOPG supports

“…Using a value, the relaxation time for metallic Au nano-particles is estimated to be 2 fs at V = 3 nm 3 (n A = 177) and 0.04 fs at V = 30 nm 3 . If a is fixed for a photoelectron inside the metallic region, the relaxation time s increase exponentially with decreasing V. This a value is considerably smaller than that (0.4-0.5) reported previously [13,16,18] based on the model proposed by Hövel et al [16]. Indeed, for the extremely small Au particles (nonmetal) on Sp-HOPG, we must take a larger a value ranging from 0.14 up to 0.52 and the relaxation time becomes longer above several fs to reproduce the high E B shifts.…”

“…For Au on reduced and stoichiometric TiO 2 (1 1 0), the Au 4f line shows higher binding energy shifts at small Au coverage [12][13][14]. However, the higher binding energy (E B ) shift is also induced by the effect of a photo-hole remaining on metal nano-clusters during the photoemission process, so called final state effect [12][13][14][15][16][17][18][19]. Therefore, it is crucial to characterize the final state effect in terms of size and shape of Au nano-particles and of dependence upon support species quantitatively.…”

Femtosecond dynamic final-state effect in photoemission of surface-passivated metallic nanoparticles on graphite substrates

“…The size distributions and shapes of the synthesized dodecanethiolate-(DT-) and octadecanethiolate-(ODT-) passivated nanoparticles were characterized by ex-situ observations with transmission electron microscope (TEM). The detailed experimental procedures are described elsewhere [12][13][14]. Ultraviolet photoemission (UPS) measurements were performed at 40 K with the He I resonance line (hν=21.2 eV) as the excitation source at Tohoku University.…”