(318f) Charge Transfer Structure-Reactivity Dependence of Fullerene/Single-Walled Carbon Nanotube Heterojunctions | AIChE

(318f) Charge Transfer Structure-Reactivity Dependence of Fullerene/Single-Walled Carbon Nanotube Heterojunctions

Authors 

Hilmer, A. J. - Presenter, Massachusetts Institute of Technology
Tvrdy, K., Massachusetts Institute of Technology
Zhang, J., Massachusetts Institute of Technology
Strano, M., Massachusetts Institute of Technology



Charge transfer at the interface between single-walled carbon nanotubes of distinct chiral vectors and fullerenes of various molecular weights is of interest both fundamentally and because of its importance in emerging photovoltaic and optoelectronic devices.  One approach for generating isolated, discretized fullerene/SWCNT heterojunctions for spectroscopic investigation is to form an amphiphile from the former to disperse the latter at the single-SWCNT level in aqueous solution.  Herein, we synthesize a series of methanofullerene amphiphiles, including derivatives of C60, C70, and C84, and investigated their electron transfer with SWCNT of specific chirality, generating a structure/reactivity relationship.  For C61 and C71 methanofullerenes, the driving force for photoexcited electron transfer from SWCNT is small, and therefore significant decreases in the relative SWCNT fluorescence yield are only observed in the limit of high surface coverage of the methanofullerene moiety.  In the case of 29% and 26% surface coverage by the C61 and C71 methanofullerenes, respectively, only a partial quenching of nanotube fluorescence was observed across all species.  In the case of C61 it was observed that near-complete quenching could be obtained by increasing the surface coverage of C61 to 92%.  In contrast, in the case of C85 methanofullerene, even at a predicted SWCNT surface coverage of only 14%, this fullerene derivative shows complete quenching of all semiconducting SWCNT utilized in this work.  This enhancement in quenching efficiency is consistent with the deeper LUMO level of C85 methanofullerene over comparatively smaller fullerene adducts, and suggests its promise as for SWCNT/fullerene heterojunctions.  The relative rates of charge transfer for C61 and C71 complexes with SWCNT of varying bandgap are well described by a Marcus theory based structure-reactivity relationship.