Strong visible photoluminescence from hollow silica nanoparticles

Starting with crystalline silicon nanoparticles, which were produced by CO2 laser pyrolysis of silane in a gas flow reactor, we have synthesized amorphous silica nanoparticles via oxidation. Upon excitation with UV light, the novel nanostructured material gives rise to an intense red photoluminescence (PL) which resembles that of some silicon nanostructures. Transmission electron microscopy studies and electron energy loss spectroscopy confirm that the nanoparticles are composed of amorphous silica and that the majority of them are hollow. The strong red PL is attributed to defects or molecular species located at the inner and outer surfaces of the hollow nanoparticles. Its similarity to the PL of nanostructured silicon seems fortuitous.