CARBON ONIONS PRODUCED BY HEAT-TREATMENT OF CARBON SOOT AND THEIR RELATION TO THE 217.5 NM INTERSTELLAR ABSORPTION FEATURE

A new material containing macroscopic quantities of hollow nanometric carbon onions with from 2 to about 8 graphitic shells, with outer diameters ranging from 3 to 10 nm (characterized by high-resolution electron microscopy), is produced by heat treatment of pure carbon soot. Other structures (i.e. nanotubes) are also formed. Ultraviolet spectra of suspensions of this material in water reveal an absorption band with a peak absorption at 264 nm +/- 3 nm and with widths from 1.4 to 2.0 mum-1. Several features of the absorption spectra closely resemble the interstellar absorption band at 217 nm.