Electron transfer processes on Ag and Au clusters supported on TiO2(110) and cluster size effects

Abstract

The results of a detailed study of Li(+) neutralization in scattering on Ag and Au clusters and thin films supported on TiO(2) are presented. A very efficient neutralization is observed on small clusters with a decrease for the smallest clusters. These results closely follow the size-effects observed in the reactivity of these systems. The energy dependence of the neutralization was studied for the larger clusters (>4 nm) and observed to be similar in trend to the one observed on films and bulk (111) crystals. A general discussion of possible reasons of the enhancement in neutralization is presented and these changes are then tentatively discussed in terms of progressive modifications in the electronic structure of clusters as a function of reduction in size and as it evolves from metallic-like to discretised states. The highest neutralization efficiency would appear to correspond to clusters sizes for which a metal to nonmetal transition occurs. The relative position of the Li level and the highest occupied molecular orbital in the molecular cluster can be expected to strongly affect the electron transfer processes, which in this case should be described in a molecular framework.

Ion Beam Induced Formation and Interrogation of Au Nanoclusters

“…To study the effects of roughness, a clean polycrystalline Au foil was sputtered with Ar under the same experimental conditions used for sputtering the Au film on TiO 2 , but no concurrent changes in the scattered alkali-metal ion neutralization were observed. It was also previously observed that Ar sputtering of a Au foil [13] and Au(111) [15] does not change the surface work function or increase the neutralization during alkali-metal ion scattering. Therefore, the increase of NF with sputtering of Au clusters on TiO 2 cannot be explained simply by a change of surface roughness.…”

“…The energy of the scattered projectile can be used to separate the signal from the nanocluster from that of the support. This technique has recently been able to detect the confined states of vapor deposited Au [13,14] and Ag [15] nanoclusters.…”

Li+-ion neutralization on metal surfaces and thin films

“…Thus scattering on clusters and monolayer thin films has attracted attention [24][25][26]. Experimental studies of alkalimetal neutralization on supported Ag and Au clusters were performed [24,25] in the quest of observation of quantum-size effects [27][28][29], and showed that alkali-metal neutralization proceeds much more efficiently on small clusters than on films or bulk metal surfaces. Recent theory has also addressed the case of electron transfer on ultrathin films [30,31] and the effect of quantization because of the finite thickness of the film.…”

High-performance parallel solver for 3D time-dependent Schrodinger equation for large-scale nanosystems

“…Furthermore, the electron exchange in nanosystems also exhibits such interesting phenomena as quantum-size effects [16,17,18,19,20] and quantum vortices [21].…”