Fullerenes to form directly out of graphene

May 09, 2010

ULM / NOTTINGHAM - A detailed observation of the dynamic transformations of graphene published today show unambigously that close-cage fullerene structures are formed directly from flat sheets of graphene.

Many scientists regard Buckminster fullerene (C60) as the most iconic molecules of the 20th century. Their discovery in 1985 sparked a wave of research into carbon nanostructures, leading to the discovery of carbon nanotubes and more recently to the re-discovery of graphene. Considering their fundamental importance, the fact that 23 years after the discovery the actual pathways of fullerene formation still remained unknown comes as a big surprise. Empirical observations indicated that C60 and C70 fullerenes form from graphite in a disproportionally high yield compared to other carbon species. Various sophisticated models of their formation involving multiple steps and series of intermediates have been proposed over the years. Eventually the scientific community reached a consensus that graphite must disintegrate into very small fragments of carbon (such as C2), which then join together to form a fullerene via complex mechanisms of molecular collisions and rearrangements. Although these ideas are now widely accepted and already enshrined in numerous textbooks, scientific intuition signals that there should be a simpler and more intuitive pathway for the transition of graphite to fullerene.

Up until now there were no experimental methods that would allow the following of the formation of fullerenes from graphite. The recent advent of aberration corrected high-resolution transmission electron microscopy (AC-HRTEM) has started changing the way we study molecules. On one of the world's first commercially available AC-HRTEM microscope at Ulm University (FEI Titan 80-300 microscope with imaging-side spherical aberration-corrector), scientists of the group of Electron Microscopy for Materials Sicence (EMMS) enabled the observation of the molecules with atomic resolution and captured their structural transformations with video rate.

Watch a video of the transformation.

This latest observations of the dynamic transformations of graphene showed unambiguously that close-cage fullerene structures are formed directly from flat sheets of graphene. The experimental discovery is backed up by a quantum chemistry model developed by scientists at the University of Nottingham, showing that this process is thermodynamically driven. The scientists believe that this study may radically change the current understanding of fullerene formation, which also may have implications for technologically highly significant carbon nanotube formation.

Due to electron beam damage, the observation of molecules with high resolution transmission electron microscopy is currently limited to short periods or not possible at all. With the development of low-voltage electron microscopy in the SALVE I-II project, the scientists of the group of EMMS want to reduce the electron-beam induced damage of molecules and thus extend the possibilities to study their formation.

About the article

Title: Direct transformation of graphene to fullerene

Authors: Chuvilin, A., J. C. Meyer, U. A. Kaiser, E. Bichoutskaia, N. A. Besley, A. N. Khlobystov

Publication: Nature Chemistry