Charge stabilizing tris(triphenylamine)-zinc porphyrin–carbon nanotube hybrids: synthesis, characterization and excited state charge transfer studies

Abstract

Functionalization of single-walled (SWCNTs) and double-walled carbon nanotubes (DWCNTs) with a charge stabilizing zinc porphyrin functionalized with triphenylamine entities has been accomplished. The synthetic approach involved the reaction of tris-(triphenylamine)porphyrinato zinc(ii) with iodobenzene functionalized nanotubes through a Sonogashira C-C cross coupling reaction under microwave irradiation conditions. Evidence of covalent functionalization and the extent of functionalization was obtained from systematic studies carried out by AFM, TGA, XPS and Raman spectroscopy techniques. The porphyrin-nanotube interactions in the SWCNT-porphyrin hybrid were probed by studies involving optical absorbance, Raman spectroscopy, steady-state and time resolved emission and electrochemical studies. The fluorescence of porphyrin in this hybrid was found to be quenched due to interactions with the CNTs. Femtosecond transient absorption spectral studies covering both the visible and near-infrared regions were supportive of excited state charge transfer interactions in the zinc porphyrin-SWCNT. The charge separated state was persistent for about 1 ns. Electron pooling experiments suggested that this donor-acceptor nanohybrid could be a useful photocatalyst.

Graphene and Carbon‐Nanotube Nanohybrids Covalently Functionalized by Porphyrins and Phthalocyanines for Optoelectronic Properties

“…Functionalization of SWCNTs and DWCNTs with a charge‐stabilizing zinc porphyrin containing triphenylamine moieties has been accomplished by Sonogashira coupling . Free‐radical addition of SWCNTs/DWCNTs with a 4‐iodobenzenediazonium salt (generated in situ from 4‐iodoaniline and isoamyl nitrite) afforded iodophenyl groups on the sidewalls of the CNTs.…”

“…The CS state of ZnPor–CNT nanohybrids is stabilized by attaching a secondary donor (triphenylamine) to the ZnPor meso positions; femtosecond TA spectra of the hybrids revealed peaks in the 700–740 and 1000–1200 nm ranges where the [(TPA) 4 ZnPor] + absorbance was expected, with the charge‐separated state persisting for ≈1 ns.…”

Interfacing porphyrins and carbon nanotubes through mechanical links

“… 1 – 5 A particularly active area of research is the combination of porphyrins and carbon nanotubes (CNT), which also benefits from the extraordinary physical properties of CNTs. 6 – 9 Porphyrin–CNT hybrids have been successfully applied to the fabrication of bioinspired high-performance gas sensors, 10 , 11 catalysts, 12 – 15 model photosynthetic systems, 16 – 18 and other optoelectronic devices. 19 The physical properties of all these artificial systems depend crucially on the nature of the linker between them.…”

N-Doped graphene/C60covalent hybrid as a new material for energy harvesting applications

“…In addition, the surface composition (atom percentages) was evaluated from peak intensities normalized with atomic sensitivity factors, 33 , 34 (see Table S2 in the ESI † ). It was found that the percentage of nitrogen in N-G/C 60 4 decreases with respect to the N-G precursor.…”

“…We have successfully used this strategy in the past to demonstrate charge separation and utilization of a charge-separated state in photocatalytic applications in nanocarbon-derived donor–acceptor hybrids. 33 , 41 , 42 …”