Preparation and Photoelectrochemical Properties of Fullerene Modified ITO Electrodes Using Self-Assembled Monolayer

Abstract

Fullerene (C60) immobilized indium-tin-oxide (ITO) electrodes were prepared by a technique of self-assembled monolayers (SAMs) using five compounds of alkyldiamine (NH2(CH2)nNH2; n＝4, 6, 8, 10 and 12). These C60／diamine-SAMs modified ITO (C60／n／ITO; n＝4,6,8, 10 and 12) electrodes were examined in terms of properties of electrochemical and photoelectrochemical responses. The C60 surface coverage of C60／n／ITOs estimated was ca. 3×10 -10 to 4×10 -10 mol cm -2 . The stable anodic photocurrent appeared immediately after the irradiation of the C60／n／ITO electrode in 0.1 M Na2SO4 containing 50 mM ascorbic acid (AA) as an electron sacrificer with λ ＝400-600 nm, light power of 4.0-6.5 mW cm -2 and electrode potential of -0.15 V to ＋0.15 V vs. Ag／AgCl (saturated KCl). The photocurrents generated by C60／ n／ITOs increased with the number of the methylene unit (n) except for n＝12. These results have shown that increasing the length of the methylene contributes to only immobilization of C60, because of highly ordered structure of diamine-SAMs. 1．Introductionety onto ITO , 8) gold 9) surfaces have been reported previously. Because diamine show pronounced reacRecently , many researchers have studied on tivity to both C60 and ITO, they have been employed fullerene (C60) thin films formed using a variety of as prelayer of immobilized C60. cells, 10, 11) methods as Langmuir-Blodgett (LB) techniques and Organic-based photovoltaic which evaporation. 1) These C60 thin films have exhibited inmimic photoinduced multistep electron transfer procteresting electrochemical, photochemical and optical esses in photosynthesis, 12～14) have been developed in properties. However , the instability and the defect recent years. Photosynthesis is among the most charhave disadvantaged practical application of these sysacteristic examples of complicated molecular assemtems to molecular devices . Similarly , these phyblies in nature. In the photosynthesis system, followsisorbed fullerene thin films lack the stability and ing mutistep electron transfer takes place from the diuniformity at the nano-scale level . Several studies mer of chlorophyll to the quinines along the wellhave previously reported C60-containing selfarranged pigments fixed in the protein matrix, leadassembled monolayers (SAMs) immobilized onto the ing to the generation of a long-lived , chargesurfaces of gold , 2～4) indium-tin-oxide ( ITO ) 5) and separated state with nearly 100 ％ quantum yield . silicon dioxide. 6) SAMs are an interesting method forThe importance of molecular aggregates in nature has constructing highly ordered and densely packed encouraged us to assemble function molecules in artistructures on substrates. But, synthesis and preparaficial manner without the assist of protein. Covalent tion of self-assembling compounds linkage with the attachment of functional molecules to the terminal of C60 moiety was very arduous. Therefore, another apSAMs has been pursued to construct well-organized proach for immobilization of C60 onto the ITO surmolecular assemblies containing p...

Development of Fullerene Thin-Film Assemblies and Fullerene-Diamine Adducts towards Practical Nanocarbon-Based Electronic Materials

“…41 The fabrication and photolelectrochemical properties of C 60 -modified ITO electrodes via alkyldiamines were reported by Ozawa et al (Figure 7). 35 At first, ITO transparent electrodes were immersed into a solution of primary aliphatic diamines with various chain lengths to form self-assembled monolayers of alkyldiamines on the ITO surface. As a result, the amino group as a reaction point to C 60 was utilized on the surface.…”