JAPAN NANONET BULLETIN - 44th Issue - May 12, 2005

YOUNG RESEARCHERS’ INTRODUCTION

Atsushi IKEDA

Associate Professor, Graduate School of Materials Science, Nara Institute of Science and Technology

1992	Research Fellowships for Young Scientists, Japan Society for the Promotion of Science(JSPS)
1994	Doctor of Engineering, Faculty of Engineering, Kyushu University
1995	Research Associate, Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
2001~ 2003	Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Conversion and Control by Advanced Chemistry, Japan Science and Technology Corporation (JST)
2002~ present	Associate Professor, Graduate School of Materials Science, Nara Institute of Science and Technology
E-mail:	Web Page

Atsushi IKEDA
Associate Professor, Graduate School of Materials Science, Nara Institute of Science and Technology

Novel photocurrent generators constructed by supramolecular assembly

(Issued in Japanese: December 23, 2003)

There has been great interest devoted to the development of photocurrent generators consisting of organic electron-donor and electron-acceptor couples. These electron-donors or electron-acceptors can be deposited on the electrode surface as monolayers by means of Langmuir-Blodgett (LB) membranes and self-assembled monolayers (SAMs). However, it is very difficult to link covalently all of the thin-layer-forming substituents, donor units and acceptor units into one molecular system through synthetic methods. To find a more expeditious and more general means of designing a multilayer photocurrent generator system on an electrode, we have taken advantage of a method known as alternate adsorption. A C₆₀-porphyrin dyad system produced by alternate adsorption showed a sensitive photoelectrochemical response under visible light irradiation and a high quantum yield (20%). The largest advantage of the alternate adsorption method is its easiness as it utilizes self-assembly while maintaining a high quantum yield.

The preparation of thin films with high surface concentrations of donor-acceptor molecules is indispensable in order to achieve high conversion efficiency, but it inevitably induces self-aggregation of the chromophores. After photoactivation, therefore, the aggregated donor or acceptor molecules on the electrode will be deactivated by self-quenching. It thus occurred to us that the self-aggregation might be suppressed by encapsulation of the donor or acceptor molecules in the cavity of macrocyclic host molecules. The photocurrent density and the quantum yield in the C₆₀-porphyrin bilayer system are remarkably improved by the addition of cyclodextrin. The high quantum yield arises from the isolation of the porphyrin units by cyclodextrin through host-guest interactions.

Further applications of this new concept are currently being examined in this laboratory.

Fig. 1

Adsorption of a host-guest complex on an electrode.

Fig. 2

Preparation of self-assembled multilayers of C₆₀ and porphyrin by a convenient alternate adsorption method.

Relevant papers

Ikeda, A., Hatano, T., Shinkai, S., Akiyama, T. & Yamada, S.
Efficient Photocurrent Generation in Novel Self-Assembled Multilayers Comprised of [60]Fullerene-Cationic Homooxacalix[3]arene Inclusion Complex and Anionic Porphyrin Polymer
J. Am. Chem. Soc., 123(20), 4855-4856 (2001).
Hatano, T., Ikeda, A., Konishi, T., Kikuchi, J. & Shinkai, S.
Facile Deposition of [60]Fullerene on the Electrode by Electrochemical Oxidative Polymerization of Thiophene
Chem. Commun., 2003(3), 342-343.
Ikeda, A., Hatano, T., Konishi, T., Kikuchi, J. & Shinkai, S.
Host-guest Complexation Effect of 2,3,6-Tri-O-methyl-b-cyclodextrin on a C₆₀-Porphyrin Light-to-Photocurrent Conversion System
Tetrahedron, 59 (19), 3537-3540 (2003).