Structural and optical characteristics of fullerenes incorporated inside porous silica aerogel

The successful synthesis of fullerene-doped silica aerogel by the sol-gel process followed by the supercritical drying technique is reported. The fullerenes (C60/C70) can be embedded inside micropores linked by the silica skeleton and the fullerene structures were retained in the fabrication process as seen using mass spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. The fulleren-doped composites were found to be able to emit intense visible light (2.26 eV) under Ar+ laser (488 nm) excitation at room temperature. The luminescent intensity increased strongly with low doping of fullerenes (0.05 mol%), then decreased while the peak was red-shifted and finally quenched upon heavy doping (2.5 mol%). This phenomenon is explained as a result of the quantum confinement effect for fullerenes which produces emissions far above the inter-band gap of C60/C70.