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

TL;DR

This study investigates ultraviolet photoluminescence in sol-gel silica glasses, revealing the formation of polycyclic hydrocarbons like naphthalene and pyrene from ethanol, which influence the material's luminescent properties.

Contribution

It is the first to identify specific polycyclic hydrocarbons responsible for UV luminescence in sol-gel silica glasses, linking their formation to ethanol-derived carbon groups.

Findings

UV PL bands at 3-4 eV are linked to polycyclic hydrocarbons.

Polycyclic hydrocarbons such as naphthalene and pyrene are formed during glass consolidation.

PL activity is related to embedded aromatic carbon groups.

Abstract

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.