Electrophoretic Deposition of Single-Walled Carbon Nanotubes Covalently Modified with Bulky Porphyrins on Nanostructured SnO2 Electrodes for Photoelectrochemical Devices

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• 作者：Tomokazu Umeyama ; Mitsuru Fujita ; Noriyasu Tezuka ; Naoki Kadota ; Yoshihiro Matano ; Kaname Yoshida ; Seiji Isoda ; Hiroshi Imahori
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：August 2, 2007
• 年：2007
• 卷：111
• 期：30
• 页码：11484 - 11493
• 全文大小：236K
• 年卷期：v.111,no.30(August 2, 2007)
• ISSN：1932-7455

文摘

Single-walled carbon nanotubes (SWNTs) covalently modified with large porphyrin molecules have beenprepared to construct photoelectrochemical devices with nanostructured SnO₂ electrodes on which themultiporphyrin-linked SWNTs are deposited electrophoretically. The film of the porphyrin-linked SWNTson the nanostructured SnO₂ electrode exhibited an incident photon-to-photocurrent efficiency as high as 4.9%under an applied potential of 0.08 V vs SCE. The more uniform film and moderate photocurrent generationin the porphyrin-linked SWNT devices can be rationalized by the exfoliation abilities of the bulky porphyrinsthat yield large steric hindrance around the SWNTs. Direct electron injection from the excited states of theSWNTs to the conduction band of the SnO₂ electrode is responsible for the photocurrent generation. Despitethe efficient quenching of the porphyrin-excited singlet state by the SWNTs in the porphyrin-linked SWNTs,the photocurrent action spectra revealed that the excitation of the porphyrin moieties makes no contributionto the photocurrent generation. The evolution of an exciplex between the porphyrin-excited singlet state andthe SWNTs and the subsequent rapid decay to the ground state without generating the charge-separated stateis proposed to explain the unusual photoelectrochemical behavior. The results obtained here will providevaluable information on the design of SWNT-based photoelectrochemical devices.