Ultraviolet luminescence of polycyclic aromatic hydrocarbons in partially consolidated sol-gel silica glasses

•Structured ultraviolet luminescence bands in silica glass are related to carbon.•Bands in 3.7 eV–3.8 eV region are due to interstitial naphthalene molecules.•Bands in 3.1 eV–3.3 eV region are due to interstitial pyrene molecules.•Polycyclic hydrocarbons in silica glass matrix are thermally stable up to 1000 °C.•They may serve as a source of carbon ring structures in C-doped silica. Photoluminescence (PL) and Raman spectra of sol-gel-derived silica glasses were studied in course of the consolidation of xerogel to dense glass. A number of ultraviolet PL bands in 3 eV–4 eV region were found, which have not been observed in pure silica glasses not exposed to carbon compounds. Such PL bands, some of which exhibit distinct vibronic structures at room temperature, have been persistently reported in various high-surface porous or nanoparticle forms of SiO2. Based on their spectral shapes and decay kinetics properties, the structured PL bands in the 3.7–3.8 eV and 3.1–3.3 eV regions are assigned to polycyclic hydrocarbons, naphthalene and pyrene, respectively, which are formed from ethanol molecules created by hydrolysis of tetraethoxysilane. These data support the hypothesis that PL activity of carbon-doped silica may be related to embedded aromatic carbon groups.