Nanocones extend the graphene toolbox

Graphene, buckyballs, and carbon nanotubes now have a new family member, the nanocone, adding to the types of all-carbon nanostructures with remarkable electronic and optical characteristics and bringing its own promising properties. (J. Am. Chem. Soc., 2019, DOI: 10.1021/jacs.9b06617) Such molecules could be useful for developing efficient organic solar cells or as sensor molecules.

Organic chemist Frank Würthner and postdoctoral researcher Kazutaka Shoyama of the University of Würzburg came up with the method for synthesizing the nanocones, which are 1.68 nm in diameter and 0.432 nm tall. A five-atom ring of carbons forms the cone’s tip. The team used a cross-coupling annulation cascade to add hexagons around the edges of the ring until the molecule grew to 80 carbons. The team added five nitrogen atoms around the periphery of the cone, increasing the crystal’s solubility.

The cones could prove more soluble in organic solvents than graphene; solubility is necessary for making thin-films to build devices, such as solar cell components, out of the material. The nanocones also absorbed light across most of the visible spectrum better than fullerenes. Like fullerenes, they were also electron poor. Those two properties could make them useful for creating efficient organic solar cells, the authors say, and the nanocones’ fluorescence could make them useful in sensor applications. The overall yield of the full-size cone was low, however, just 0.6%, because of the strain induced by the molecule’s cone shape.