Carbon-Promoted in Situ Evolution of Cu Nanoclusters Influencing Eu3+ Photoluminescence in Glass: Bidirectional Energy Transfer
The present work explores the use of carbon powder, recently proposed for producing plasmonic metal nanocomposites, as a means to obtain Eu3+ photoluminescence (PL) enhancements via Cu nanoclusters in glass. Phosphate glasses containing Eu2O3 and CuO were prepared by melting in ambient atmosphere with graphite powder added to the batch materials for the chemical reduction of copper(II). Optical absorption and PL spectroscopy characterizations, including emission decay dynamics, were performed. The data show consistently the effective reduction of Cu2+ ions via carbon during melting which ultimately leads to thermally induced copper particle precipitation. Further, the novel in situ concurrent PL and absorption microspectroscopy technique was employed for the real-time monitoring of the optical properties of the codoped glasses during thermal processing from 470 to 490 °C. Bidirectional energy transfer between europium ions and copper nanoclusters has been manifested through enhancement and quenching regimes of Eu3+ PL. These periods were observed well separated in time, favorable for the optical tuning of the solid-state luminescent material. Relating simultaneously the luminescence with the time evolution in optical absorption allowed for discriminating the effects of Cu preplasmonic clusters as energy donors and Cu nanoparticles as acceptors, to and from Eu3+ ions, respectively.