Hydrogen-Driven Cage Unzipping of C60into Nano-Graphenes.
Annealing of C60in hydrogen at temperatures above the stability limit of C-H bonds in C60Hx(500-550 °C) is found to result in direct collapse of the cage structure, evaporation of light hydrocarbons, and formation of solid mixture composed of larger hydrocarbons and few-layered graphene sheets. Only a minor part of this mixture is soluble; this was analyzed using matrix-assisted laser desorption/ionization MS, Fourier transform infrared (FTIR), and nuclear magnetic resonance spectroscopy and found to be a rather complex mixture of hydrocarbon molecules composed of at least tens of different compounds. The sequence of most abundant peaks observed in MS, which corresponds to C2H2mass difference, suggests a stepwise breakup of the fullerene cage into progressively smaller molecular fragments edge-terminated by hydrogen. A simple model of hydrogen-driven C60unzipping is proposed to explain the observed sequence of fragmentation products. The insoluble part of the product mixture consists of large planar polycyclic aromatic hydrocarbons, as evidenced by FTIR and Raman spectroscopy, and some larger sheets composed of few-layered graphene, as observed by transmission electron microscopy. Hydrogen annealing of C60thin films showed a thickness-dependent results with reaction products significantly different for the thinnest films compared to bulk powders. Hydrogen annealing of C60films with the thickness below 10 nm was found to result in formation of nanosized islands with Raman spectra very similar to the spectra of coronene oligomers and conductivity typical for graphene.
Department of Physics, Umeå University , SE-901 87 Umeå, Sweden.
Alexandr V
AV
Talyzin
Department of Physics, Umeå University , SE-901 87 Umeå, Sweden.
Serhiy
S
Luzan
Department of Applied Physics, Aalto University , P.O. Box 15100, FI- 00076 Aalto, Espoo, Finland.
Ilya V
IV
Anoshkin
Department of Applied Physics, Aalto University , P.O. Box 15100, FI- 00076 Aalto, Espoo, Finland.
Albert G
AG
Nasibulin
Department of Applied Physics, Aalto University , P.O. Box 15100, FI- 00076 Aalto, Espoo, Finland.
Esko I
EI
Kauppinnen
Department of Physics and Electrical Engineering, Karlstad University , SE-651 88 Karlstad, Sweden.
Andrzej
A
Dzwilewski
National Institute of Chemistry , 19 Hajdrihova, Ljubljana 1000, Slovenia.
Ahmed
A
Kreta
National Institute of Chemistry , 19 Hajdrihova, Ljubljana 1000, Slovenia.
Janko
J
Jamnik
National Institute of Chemistry , 19 Hajdrihova, Ljubljana 1000, Slovenia.
Abdou
A
Hassanien
Department of Chemistry-BMC, Uppsala University , Box 576, SE-751 23 Uppsala, Sweden.
Anna
A
Lundstedt
Department of Chemistry-BMC, Uppsala University , Box 576, SE-751 23 Uppsala, Sweden.
Helena
H
Grennberg