Photoluminescence of atomic gold and silver particles in soda-lime silicate glasses

Abstract

We report the chemistry and photophysics of atomic gold and silver particles in inorganicglasses. By synchrotron irradiation of gold-doped soda-lime silicate glasses we could create andidentify unambiguously the gold dimer as a stable and bright luminescing particle embedded inthe glassy matrix. The gold dimer spectra coincide perfectly with rare gas matrix spectra ofAu2. The glass matrix is, however, stable for years, and is hence perfectly suitedfor various applications. If the irradiated gold-doped sample is annealed at550 °C a bright green luminescence can be recognized. Intense 337 nm excitation inducesa decrease of the green luminescence and the reappearance of the 753 nmAu2 emission, indicating a strong interrelationship between both luminescence centers.Time-dependent density functional theory (TD-DFT) calculations indicate that the greenluminescence can be assigned to noble metal dimers bound to silanolate centers. Thesecomplexes are recognized as the first stages in the further cluster growth process, which hasbeen investigated with small-angle x-ray scattering (SAXS). In silver-doped glasses,Ag0 atoms can be identified with electron paramagnetic resonance(EPR) spectroscopy after synchrotron activation. Annealing at300 °C decreases theconcentration of Ag1, but induces an intense white light emission with 337 nm excitation. The white luminescencecan be decomposed into bands that are attributed to small silver clusters such asAg2,Ag3 and Ag4, and an additional band matching the green emission of gold-doped glasses.