Ag Site in Ag-for-Na Ion-Exchanged Borosilicate and Germanate Glass Waveguides

Abstract

The Ag site in Ag-for-Na ion-exchanged borosilicate and germanate waveguides has been investigated by EXAFS spectroscopy. In contrast with the results generally reported in literature, it is shown that, for both silicate and germanate waveguides, the Ag site is strongly dependent on the Ag content and the Ag-O distance is longer for higher doping levels. It is demonstrated that this trend is related to a structural rearrangement of the Ag site in the whole doped layer; the EXAFS results on the samples that underwent the ion exchange at higher temperatures and the comparison with literature data suggest that the sites with shorter distances are more stable. The correlation between local structure around Ag and the photoluminescence properties of the borosilicate waveguides is established. In particular, the red shift of the blue band observed in the absorption and excitation spectra by increasing the Ag concentration has been univocally related to the increase of the Ag-O bond length

Core–shell-like Au sub-nanometer clusters in Er-implanted silica

“…Nevertheless, if this would be the case, the effective coordination number of this O shell would be about 3-4 for at least two cases, to be compared with the coordination number of ≈2 experimentally found for other noble metal ions, such as Ag, introduced in solid glass matrices. 17 Considering also that the Gibbs free energy for Auoxide formation is the highest among those of transition metal oxides, a O coordination at the cluster surface seems to be more reasonable, further supporting the picture of core-shelllike clusters. The Au-O coordination distance varies in a nonmonotonic way (Table 1) with the annealing temperature.…”

“…X-ray absorption spectroscopy (XAS) performed at the metal edge is a suitable technique to monitor metal nucleation and the first steps of growth since it can detect both oxide phases 17 and the formation of clusters, 14,18 even in the sub-nanometer range of size. 19,20 In the case of monodisperse clusters, a detailed analysis can also give an indication of the cluster shape.…”

Effective enhancement of Bi near-infrared luminescence in silicogermanate glasses via silver–sodium ion exchange

“…On the other hand, Ag K-edge EXAFS analysis showed that Ag + ion had a CN of 2.1 with a Ag-O distance of 2.08 Å [31]. The similar behavior could be observed in other glasses [32,33]. It means that the Ag incorporation always causes local structural relaxations.…”

Au–Ag nanoalloy molecule-like clusters for enhanced quantum efficiency emission of Er3+ions in silica

“…From the EXAFS results, therefore, and considering Au and Au-Ag clusters with roughly the same size equation, which relates the interatomic distance variation to the cluster size, 18,31 we can estimate that the pure Au N and the alloy in Ag-based glass waveguides under conditions of slight supersaturation, i.e., at the onset of the Ag nucleation. 32,33 This suggests that at least part of Ag atoms at the cluster surface is covalently connected to O atoms of the matrix.…”