Spectroscopic Investigation of Structural Rearrangements in Silver Ion-Exchanged Silicate Glasses

Abstract

The silver ion environment and the microstructural rearrangement of Ag+-Na+ ion-exchanged glasses were investigated by means of micro-Raman and photoluminescence spectroscopies. The samples were produced by immersing borosilicate glasses in NaNO3:AgNO3 molten salts baths with different molar ratios of silver nitrate. The modifications of the silica network microstructure were inspected by analysis of the Raman peak at about 1100 cm-1, and the evolution with the silver concentration at the glass surface of the spectral components related to the different silica tetrahedral groups was studied. The formation of silver metal nanoparticles was inferred from the occurrence of the low-frequency Raman peak due to confinement of acoustic vibrations in metal clusters, and their dimensions were evaluated from the position of its maximum. In the light of the structural analyses performed by means of Raman spectroscopy, a final assignment of the different luminescence bands of silver embedded in silicate glasses was attained

Investigation of the role of silver species on spectroscopic features of Sm3+-activated sodium–aluminosilicate glasses via Ag+-Na+ ion exchange

“…[17][18][19][20][21][22][23] In fact, the outermost electron 4d 10 -4d 9 5s 1 transitions of silver ions give rise to typical luminescence features whose shape and position depend on the local ion environment and on the formation of aggregates or dimers in the glass matrix. 19 In particular, four main features have been identified: a UV band around 350 nm, which is attributed to Ag þ spin-allowed transitions from the 1 D 2 state to the 1 S 0 ground state under about 250 nm excitation; 23 a violet band at about 420 nm, which is attributed to Ag þ spin-forbidden transitions of the type 3 D 1À3 -1 S 0 ; 19,21 a deep-blue band at about 450 nm attributed to (Ag 2 ) þ ; 11,18,20,24 and a green band at about 525 nm attributed to Ag þ -Ag þ pairs. 11,17,19,22,24 The excitation source that could be used to generate blue and green emission is about 350 nm UV light.…”

Effect of silver ions and clusters on the luminescence properties of Eu-doped borate glasses

“…This band may be attributed to the 4f 6 5d→4f 7 transition of Eu 2+ ions, the details of which are discussed in our previous work [20,21]. Interestingly, Eu 2+ and Eu 3+ ion emissions between 575 and 675 nm, assigned to 5 D 0 -7 F J (J= 0-4) transitions, increased with increasing Ag ion content [22,23]. Moreover, another broad shoulder band at 500 nm was also observed; this result agrees well with previous studies describing the characteristic emission of Ag clusters from 400 nm to 700 nm upon excitation at 350 nm [6].…”

“…4(a). Prior to silver ion exchange, weak Eu 2+ ion emission bands may be observed at 438 nm; after inclusion of silver ions into the host, however, 410 nm emission bands related to the 3 D 1 → 1 S 0 transition of isolated Ag + are observed [4,23]. At the same time, the increased Eu 3+ emission at 615 nm confirmed the energy contribution of silver ions on the radiative transition process.…”

Silver doping of glasses

“…As a matter of fact, the process of silver incorporation is often governed by non-equilibrium mechanisms that involve internal local feedbacks between the variables that drive the silver behavior, often preventing classical descriptions based on thermodynamic, chemistry and diffusion equations. In this sense, several spectroscopic investigations have been performed on the structural rearrangements in silicate glasses doped with silver by different non-equilibrium techniques [30][31][32][33] looking on one hand at a deeper understanding of the silver behavior in the matrix, and on the other hand at a comprehensive phenomenological descripition able to provide suitable recipes for the fabrication of glasses with prescribed features. The diffusion behavior of silver in glasses has been also di object of several dedicated studies: the classical phenomenology of the Nernst-Planck equations, as first described for this case by Doremus [34], has been tested for several Ag-glass systems, demonstrating the need to include local effects of both compositional (pseudo mixed-alkali effect) and electrical (local fields build-up) nature [35][36][37][38], In this perspective, the electrical conductivity properties of silverdoped glasses has been also extensively studied [39][40][41][42] for application purposes.…”