Gold Atoms and Dimers on Amorphous SiO₂:  Calculation of Optical Properties and Cavity Ringdown Spectroscopy Measurements

Abstract

We report on the optical absorption spectra of gold atoms and dimers deposited on amorphous silica in size-selected fashion. Experimental spectra were obtained by cavity ringdown spectroscopy. Issues on soft-landing, fragmentation, and thermal diffusion are discussed on the basis of the experimental results. In parallel, cluster and periodic supercell density functional theory (DFT) calculations were performed to model atoms and dimers trapped on various defect sites of amorphous silica. Optically allowed electronic transitions were calculated, and comparisons with the experimental spectra show that silicon dangling bonds [[triple bond]Si(.-)], nonbridging oxygen [[triple bond]Si-O(.-)], and the silanolate group [[triple bond]Si-O(-)] act as trapping centers for the gold particles. The results are not only important for understanding the chemical bonding of atoms and clusters on oxide surfaces, but they will also be of fundamental interest for photochemical studies of size-selected clusters on surfaces.

First-principles study on adsorption of Au atom on hydroxylated SiO2 surface

“…The geometry optimization of the substrate provided some parameters of the absorption substrate, the bond lengths of and are 0.97 and 1.63 Å, and the angle of 118.7º, respectively, consistent with those in literatures [27,28] .…”

“…The adsorptions of metal atoms on TiO 2 and Al 2 O 3 surfaces have been investigated using density functional theory as well [14][15][16][17] . SiO 2 used as a largely covalent supporting oxide to adsorb metal atoms has also been simulated by the first quantum-mechanical study [18][19][20][21][22] . Although many theoretical studies of metal/SiO 2 system have been performed, the interaction of metal atoms or clusters with the surface of oxide is still conjectural and needed to further study.…”

Gold-based nucleation in implanted silica studied by x-ray absorption spectroscopy

“…The Au-O coordination is likely related to Au atoms dispersed into the matrix and oxidized as well as to Au atoms at the cluster surface, interacting with the matrix. The Au-O interatomic distance is well comparable with the results of the simulations for Au atoms and dimers onto silica surface [23]. It is not possible solely from a standard EXAFS analysis to distinguish between the two contributions (Au-O from cluster surface and Au-O from dispersed Au): coupling with advanced experimental setup and other characterizations is expected to help and is currently being explored [19].…”

Reduction of gold(III) chloride to gold(0) on silicate surfaces

“…Ferullo et al investigated the non-bridging oxygen defect site of silica, revealing that gold showed the smallest charge transfer from the metal to the support among the metal ions investigated [41]. On the other hand, the presence of "SiAOAAu and ["SiAOAAu] À complexes on defect sites of silica has been identified experimentally using cavity ringdown spectroscopy [42].…”