Leaving the Fullerene Road: Presence and Stability of sp Chains in sp2 Carbon Clusters and Cluster-Assembled Solids

TL;DR

This study combines experimental and theoretical methods to explore the structure and stability of sp chains within sp2 carbon clusters, revealing new nanostructures with potential functional properties.

Contribution

It demonstrates the presence of stable sp chains in disordered sp2 carbon clusters and their incorporation into nanostructured films, a novel insight into carbon nanostructure organization.

Findings

Disordered structures with coexisting sp2 and sp hybridizations form in large carbon clusters.

sp chains are encased in sp2 networks, preventing fragmentation upon deposition.

Raman spectra confirm the presence of sp/sp2 hybridization and stable sp chains.

Abstract

We report the experimental and theoretical investigation of the growth and of the structure of large carbon clusters produced in a supersonic expansion by a pulsed microplasma source. The absence of a significant thermal annealing during the cluster growth causes the formation of disordered structures where sp2 and sp hybridizations coexist for particles larger than roughly 90 atoms. Among different structures we recognize sp2 closed networks encaging sp chains. This "nutshell" configuration can prevent the fragmentation of sp species upon deposition of the clusters thus allowing the formation of nanostructured films containing carbynoid species, as shown by Raman spectroscopy. Atomistic simulations confirm that the observed Raman spectra are the signature of the sp/sp2 hybridization characteristic of the isolated clusters and surviving in the film and provide information about the structure of the sp chains. Endohedral sp chains in sp2 cages represent a novel way in which carbon nanostructures may be organized with potential interesting functional properties.