Carbon atoms can connect together to form hollow, soccer-ball shapes known as fullerenes. Sometimes, many of these hollow carbon spheres form around the exact same center point. This creates a neat structure with a small sphere nested deeply inside a larger sphere.
Chemists call these fascinating layered carbon structures fullerene onions or carbon nano-onions. Scientists create them by hitting carbon soot or tiny nanodiamonds with intense beams of electrons. They can also make them by intensely heating graphitic particles in a high-temperature annealing process.
The intense energy forces flat fragments of carbon to curl up and close into perfect spheres. The empty space between each carbon shell measures about 0.34 nanometers across. This tiny gap matches the natural spacing found between the flat layers of ordinary pencil graphite.
Because of their nested design, fullerene onions are chemically tough and will not break easily. They also offer a massive amount of usable surface area in a very tiny package. Engineers are currently testing them as catalyst supports, advanced battery electrodes, and highly efficient supercapacitors. They also work incredibly well as solid lubricants to reduce friction in tiny microscopic machines.