Mechanism of the coupling of diazonium to single-walled carbon nanotubes and its consequences.
On the tube: The coupling of diazonium ions onto single-walled carbon nanotubes is shown to proceed through a radical chain reaction by kinetic analysis of the absorption peak drop (see picture). Radical species are also revealed by ESR. Metallic (m) nanotubes play a special catalytic role in the functionalization of semiconducting (sc) nanotubes.Due to its simplicity and versatility, diazonium coupling is the most widely used method for carbon nanotube (CNT) functionalization to increase CNT processability and add new functionalities. Yet, its mechanism is so far mostly unknown. Herein, we use kinetic analysis to shed light on this complex mechanism. A free-radical chain reaction is revealed by absorption spectroscopy and ESR. Metallic CNTs are shown to play an unexpected catalytic role. The step determining the selectivity towards metallic CNTs is identified by a Hammett correlation. A mechanistic model is proposed that predicts reactivity and selectivity as a function of diazonium electrophilicity and metallic-to-semiconducting CNT ratio, thus opening perspectives of controlled high-yield functionalization and purification.
Schmidt
Grégory
G
Service de Physique de l'Etat Condensé (CNRS URA 2464), CEA Saclay Institute of Matter and Radiation, 91191 Gif sur Yvette, France.
Gallon
Salomé
S
Esnouf
Stéphane
S
Bourgoin
Jean-Philippe
JP
Chenevier
Pascale
P
D003979:Diazonium Compounds / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D015394:Molecular Structure; D037742:Nanotubes, Carbon / Q000737:chemistry*
D003979:Diazonium Compounds; D037742:Nanotubes, Carbon