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Diameter-Sorted SWCNT–Porphyrin and SWCNT–Phthalocyanine Conjugates for Light-Energy Harvesting

Authors

  • Dr. Atula S. D. Sandanayaka,

    1. School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Nomi, Ishikawa, 923-1292 (Japan)
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  • Navaneetha K. Subbaiyan,

    1. Department of Chemistry, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0051 (USA), Fax: (+1) 316-978-3431
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  • Sushanta K. Das,

    1. Department of Chemistry, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0051 (USA), Fax: (+1) 316-978-3431
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  • Dr. Raghu Chitta,

    1. Department of Chemistry, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0051 (USA), Fax: (+1) 316-978-3431
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  • Dr. Eranda Maligaspe,

    1. Department of Chemistry, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0051 (USA), Fax: (+1) 316-978-3431
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  • Dr. Taku Hasobe,

    1. Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522
    2. PRESTO (Japan) Science and Technology Agency (JST), Saitama, 332-0012 (Japan)
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  • Prof. Dr. Osamu Ito,

    Corresponding author
    1. Fullerene Group, NIMS, Namiki, Tsukuba
    2. CarbonPhotoScience Lab, Kita-Nakayama, Izumi-ku, Sendai, 981-3215 (Japan)
    • Fullerene Group, NIMS, Namiki, Tsukuba
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  • Prof. Dr. Francis D'Souza

    Corresponding author
    1. Department of Chemistry, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0051 (USA), Fax: (+1) 316-978-3431
    • Department of Chemistry, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0051 (USA), Fax: (+1) 316-978-3431
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  • Conjugates Self-Assembled via a Double-Decker Binding Strategy

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 (PyrNH3+). 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/SnO2 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/SnO2/SWCNT(7,6)/PyrNH3+:1.

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