Photoluminescence and structural properties of the nitrogen doped TiO₂ and the influence of SiO₂ and Ag nanoparticles

Mixtures of nitrogen-doped titanium dioxide (TiO₂:N) with different concentrations of Ag and/or SiO₂ particles (0.5, 1 and 2 wt.%) were prepared in solid state by mechanico-chemical interactions. Using UV–VIS spectroscopy, Raman scattering, photoluminescence (PL) and photoluminescence excitation (PLE), the influence of the particles on the host material is evaluated. UV–VIS spectroscopy studies indicate a TiO₂:N band gap shift to the UV range with increasing concentrations of SiO₂ and Ag particles. PL intensities decrease with increasing concentrations of Ag and/or SiO₂ particles in the TiO₂:N host matrix, which in turn could effectively restrict the electron and hole recombination. To explain these processes, the different de-excitation ways will be advanced, taking into account the energy levels diagram of TiO₂:N/Ag, TiO₂:N/SiO₂ and TiO₂:N/Ag/SiO₂ systems. PLE spectra show a gradual decrease in their relative intensities after 165 min of continuous irradiation due to photosensitivity of TiO₂:N. The plasmonic effect of Ag particles in the TiO₂:N/Ag system is highlighted for the first time by PLE studies. (paper)