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 coalescence of fullerenes incorporated in two different aerogel matrices, one of which was found to be reactively bonded to the silica network and the other was not. Using X-ray photoelectron spectroscopy the reactive fullerene-aerogel composite was found to possess additional chemical bonds attributed to the hydroxyl or silicon carbide bonds between fullerene and the host matrix. Under time-of-flight (TOF) laser desorption mass spectrometry the reactive composite exhibited fullerene coalescence of up to five C-60 molecules, whereas little or no coalescence was found in the nonreactive mixture. In the negative ion TOF channel 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 mechanism was due to strong interactions between the C-60 molecules and silica particles or surface species such as the H or OH group existing in the matrix.