Changes in structure and electronic states of fullerenes incorporated in silica aerogel

Abstract

We have developed a method to synthesize a novel C60-SiO2 aerogel composite with C60 concentration up to 0.2mol% by a sol-gel process accompanied by a supercritical drying technique. The structure and electronic states of the fullerenes in the new material were studied by laser desorption time-of-flight mass spectrometry, Fourier transform-infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet and visible absorption spectroscopy, and photoluminescence, all of which show distinctly different features from a previously reported C60-silica aerogel material in which the structure of C60 was found to be retained in the fabrication process. Detailed analyses of the diverse data from the different experimental techniques yield ample evidence to suggest that the structure and electronic states of the incorporated fullerene have been considerably changed, and that the C60 in the composite is passivated by surface species (most probably OH) remaining during the hydrolysis of the aerogel precursor. © 1998 Elsevier Science Ltd. All rights reserved.