Depth profiles of fullerene in ion irradiated polyimide

An analytical experimental technique is described which permits depth profiles of the fundamental molecule fullerene, C60, to be determined in solids for low molecular concentrations. The method combines a procedure for the simultaneous marking and immobilizing of fullerene in organic solids, by means of lithium salt formation, with neutron depth profiling a highly sensitive approach in determining specific depth distributions of 6Li. The new technique fullerene tracer profiling FTP is described in some detail, and results of the first experiments are discussed. Fullerene solutions have been introduced into both pristine and ion irradiated samples of the polymer polyimide PI . The C60 depth distributions were then measured using fullerene tracer profiling. From the shapes of the depth distributions conclusions are drawn concerning the uptake of fullerene solutions by polymers and the mobility of fullerene. Fullerene does not penetrate unirradiated PI, but it does readily fill up latent tracks of energetic ions in this polymer. Depending on the specific ion track density, some 104 to 107 C60 molecules can be identified as being present in a single track. The diffusion coefficient for C60 is estimated to be at least 2 10 amp; 8722;12 to 2 10 amp; 8722;13 cm2s amp; 8722;1, much higher than expected. This may be ascribed in part to the remarkable elastic deformability of the fullerene molecule in both kinetic and dynamic motion, and to the near perfect spherical geometry accompanying elimination of dangling bonds in simultaneously minimising the surface energ