title: Diameter-sorted SWCNT-porphyrin and SWCNT-phthalocyanine conjugates for light-energy harvesting.
abstract: 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.
authors.affiliation: School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Nomi, Ishikawa, Japan.
authors.forename: Atula S D
authors.initials: AS
authors.lastname: Sandanayaka
authors.forename: Navaneetha K
authors.initials: NK
authors.lastname: Subbaiyan
authors.forename: Sushanta K
authors.initials: SK
authors.lastname: Das
authors.forename: Raghu
authors.initials: R
authors.lastname: Chitta
authors.forename: Eranda
authors.initials: E
authors.lastname: Maligaspe
authors.forename: Taku
authors.initials: T
authors.lastname: Hasobe
authors.forename: Osamu
authors.initials: O
authors.lastname: Ito
authors.forename: Francis
authors.initials: F
authors.lastname: D'Souza
mesh_terms: D043844:Crown Ethers / Q000737:chemistry*; D004560:Electricity; D004566:Electrodes; D004579:Electron Transport; D007211:Indoles / Q000737:chemistry; D054833:Isoindoles; D008027:Light; D008665:Metalloporphyrins / Q000737:chemistry; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D055668:Photochemical Processes / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000737:chemistry*; D011721:Pyrenes / Q000737:chemistry; D012666:Semiconductors
chemical_list: D043844:Crown Ethers; D007211:Indoles; D054833:Isoindoles; D008665:Metalloporphyrins; D037742:Nanotubes, Carbon; D017319:Photosensitizing Agents; D011721:Pyrenes; C017802:zinc hematoporphyrin; C015762:18-crown-6; C030984:pyrene; C013647:phthalocyanine