Photoinduced electron transfer in layer-by-layer thin solid films containing cobalt oxide nanosheets, porphyrin, and methyl viologen.
The well-known layer-by-layer (LbL) method can be used to prepare solid thin films with a controlled electron transfer direction by appropriately stacking metal oxide nanosheets and functional organic ions. In this study, we prepared thin solid films consisting of cobalt oxide nanosheets (CoNSs) as the electron transfer medium, α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) as the electron donor, and 1,1'-dimethyl-4,4'-bipyridinium or methyl viologen (MV) as the electron acceptor. We investigated the photoinduced electron transfer phenomenon in these films by irradiating them with 450 nm light. Irradiating the LbL thin solid films prepared with the CoNS/TMPyP/CoNS/MV/CoNS sequence under reduced pressure led to the production of a one-electron reduction compound of MV. Hence, photoinduced electron transfer from TMPyP to MV bound to CoNSs occurred in these LbL thin solid films. However, the conduction band of CoNSs, as determined by the photoabsorption spectral and photoelectrochemical measurements, was much higher than the lowest unoccupied molecular orbital level of TMPyP. Our findings indicate that the observed equipotential photoinduced electron transfer was caused by the metallic electron conductivity of CoNSs, which show a unique charge arrangement of Co3+and Co4+. Moreover, it was also found that the observed photoinduced charge separation state has a longer life-time (>5 h) under the reduced conditions.
Department of Physics and Materials Sciences, Interdisciplinary Graduate School of Science and Engineering, Shimane University, 1060, Nishi-kawatsu-cho, Matsue 690-8504, Japan. rsasai@riko.shimane-u.ac.jp.
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http://orcid.org/0000-0002-0345-3094
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Sasai
Department of Physics and Materials Sciences, Interdisciplinary Graduate School of Science and Engineering, Shimane University, 1060, Nishi-kawatsu-cho, Matsue 690-8504, Japan. rsasai@riko.shimane-u.ac.jp.
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Kato
Department of Physics and Materials Sciences, Interdisciplinary Graduate School of Science and Engineering, Shimane University, 1060, Nishi-kawatsu-cho, Matsue 690-8504, Japan. rsasai@riko.shimane-u.ac.jp.
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Soontornchaiyakul
Department of Fine Materials Engineering, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, Japan.
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Usami
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, F3-3(250) Chikusa-ku, Furo-cho, Nagoya 464-8603, Japan.
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Masumori
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, F3-3(250) Chikusa-ku, Furo-cho, Nagoya 464-8603, Japan.
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Norimatsu
Department of Physics and Materials Sciences, Interdisciplinary Graduate School of Science and Engineering, Shimane University, 1060, Nishi-kawatsu-cho, Matsue 690-8504, Japan. rsasai@riko.shimane-u.ac.jp and Department of Applied Chemistry, Graduate School of Urban Environmental Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan.
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Fujimura
Department of Applied Chemistry, Graduate School of Urban Environmental Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan and PRESTO (Precursory Research for Embryonic Science and Technology), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Kanagawa 332-0012, Japan.
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http://orcid.org/0000-0001-7013-4942
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Takagi