Thermal effects on the surface plasmon resonance of Cu nanoparticles in phosphate glass: impact on Cu+ luminescence†
An evaluation of the effects of temperature on the optical properties of phosphate glass containing Cu nanoparticles (NPs) and Cu+ ions was carried out by means of optical absorption and photoluminescence (PL) spectroscopy measurements performed jointly in situ in the 298 to 573 K range. The surface plasmon resonance (SPR) of Cu NPs displayed a strong dampening effect with temperature, consistent with the thermal expansion of Cu NPs and an increase in the electron–phonon scattering rate. The PL of Cu+ ions in the glass with Cu NPs showed the thermal quenching effect connected with an increase in non-radiative relaxation processes. Moreover, a comparison with the precursor glass without NPs revealed that a lower activation energy for the thermal quenching of Cu+ PL results in the presence of Cu NPs for Cu+ sites emitting in resonance with the SPR. It is suggested that the increase in electron–phonon interaction in Cu NPs with temperature impacts the PL quenching of Cu+ ions the most. The current results suggest that a Cu+ → Cu NP resonant energy transfer supports a deactivation of the Cu+ emitting states with increasing temperature.