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Diameter‐Sorted SWCNT–Porphyrin and SWCNT–Phthalocyanine Conjugates for Light‐Energy Harvesting
Author(s) -
Sandanayaka Atula S. D.,
Subbaiyan Navaneetha K.,
Das Sushanta K.,
Chitta Raghu,
Maligaspe Eranda,
Hasobe Taku,
Ito Osamu,
D'Souza Francis
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100377
Subject(s) - photocurrent , phthalocyanine , photochemistry , porphyrin , carbon nanotube , materials science , photoinduced electron transfer , acceptor , absorption (acoustics) , chemistry , electron transfer , nanotechnology , optoelectronics , physics , composite material , condensed matter physics
A non‐covalent double‐decker binding strategy is employed to construct functional supramolecular single‐wall carbon nanotubes (SWCNT)–tetrapyrrole hybrids capable of undergoing photoinduced electron transfer and performing direct conversion of light into electricity. To accomplish this, two semiconducting SWCNTs of different diameters (6,5 and 7,6) were modified via π–π stacking of pyrene functionalized with an alkyl ammonium cation (PyrNH 3 + ). Such modified nanotubes were subsequently assembled via dipole–cation binding of zinc porphyrin with one ( 1 ) or four benzo‐18‐crown‐6 cavities ( 2 ) or phthalocyanine with four benzo‐18‐crown‐6 cavities at the ring periphery ( 3 ), employed as visible‐light photosensitizers. Upon charactering the conjugates using TEM and optical techniques, electron transfer via photoexcited zinc porphyrin and phthalocyanine was investigated using time‐resolved emission and transient absorption techniques. Higher charge‐separation efficiency is established for SWCNT(7,6) with a narrow band gap than the thin SWCNT(6,5) with a wide band gap. Photoelectrochemical studies using FTO/SnO 2 electrodes modified with these donor–acceptor conjugates unanimously demonstrated the ability of these conjugates to convert light energy into electricity. The photocurrent generation followed the trend observed for charge separation, that is, incident‐photon‐to‐current efficiency (IPCE) of a maximum of 12 % is achieved for photocells with FTO/SnO 2 /SWCNT(7,6)/PyrNH 3 + : 1 .