Tuning the plasmon resonance of gold nanoparticles in phase-separated glass via the local refractive index change

• Au-doped glass in the ZnO-MgO-Al2O3-SiO2 system with TiO2 and ZrO2 was prepared. • Heat-treatments of glass samples lead to the precipitation of ≈4 nm gold NPs. • Max. 100 nm redshift of the plasmon band of Au NPs was observed upon heat-treatment. • Fitting of the absorption spectra showed refractive index increase around NPs. • TiO2-contained phase-separated regions proposed to be responsible for plasmon shift. Gold-doped glasses are of interest for plasmonics and photonics as optical media with well-resolved localized surface plasmon resonance (LSPR). We showed the possibility for the thermally-controlled tuning of the LSPR band position of gold nanoparticles precipitated in the ZnO-MgO-Al 2 O 3 -SiO 2 glass nucleated by TiO 2 and ZrO 2 nucleators. The maximal red-shift of the LSPR band as high as 100 nm was achieved for glass which is characterized by the presence of 10 nm phase-separated regions and ≈ 4 nm precipitated gold nanoparticles. The fitting of the absorption spectra showed that the distinct red-shift of the LSPR band is caused by the increased refractive index of the surrounding medium (in the interval 1.6–2.6). The described scenario of the LSPR band shift driven by the phase-separation represents a new approach for precise plasmonic tuning of gold nanoparticles in glass and paves the way for the development of new glass-based materials for photonics applications.