Luminescence of silver molecular clusters in photo-thermo-refractive glasses

The luminescence spectra of silver molecular clusters in photo-thermo-refractive glasses are investigated in detail before and after the UV irradiation and also after the heat treatment of the samples. In the initial photo-thermo-refractive glass sample, silver is shown to occur in the form of Ag+ ions and positively charged molecular clusters. After the UV irradiation with the wavelength corresponding to the Ce3+ ion absorption, these species are assumed to pass partially to the neutral state, thus forming the Ag0 atoms and neutral molecular clusters such as Ag2, Ag3, and Ag4 that exhibit an intense luminescence in the visible. A subsequent heat treatment at temperatures below the glass transition one results in an increase in the intensity of the luminescence due to an increase in the concentration of neutral molecular clusters. Also investigated are the influence of halogens such as Cl and Br in glass matrix composition on the luminescence of silver molecular clusters in photo-thermorefractive glasses and the effect of temperature on the luminescence spectra of photo-thermorefractive glasses.

• UV irradiation results in transformation of charged Ag clusters to neutral ones.
• Neutral Ag clusters in glass have intense luminescence in visible.
• The intensity of luminescence of Ag clusters increase with increase of temperature.
• Increase of the NaCl or NaBr content led to the increase of luminescence intensity.