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.