GAS-PHASE AGGREGATION OF FULLERENES BY LASER-ABLATION OF FULLERENES IN REACTIVE AND NONREACTIVE MATRICES

We report an experimental study of the fragmentation/aggregation and c oalescence of fullerenes incorporated in two different aerogel matrice s, one of which was found to be reactively bonded to the silica networ k and the other was not. Using X-ray photoelectron spectroscopy the re active fullerene-aerogel composite was found to possess additional che mical bonds attributed to the hydroxyl or silicon carbide bonds betwee n fullerene and the host matrix. Under time-of-flight (TOF) laser deso rption mass spectrometry the reactive composite exhibited fullerene co alescence of up to five C-60 molecules, whereas little or no coalescen ce was found in the nonreactive mixture. In the negative ion TOF chann el the maximum peak of twice C-60 coalescence by laser desorption was always located at masses greater than 120 carbon mass units, which is different from all previous reports. We suggest that the formation mec hanism was due to strong interactions between the C-60 molecules and s ilica particles or surface species such as the H or OH group existing in the matrix.