Chain Length Effect on the Structure and Photoelectrochemical Properties of Self-Assembled Monolayers of Porphyrins on Gold Electrodes

• DOI: 10.1021/jp992768f
• Publication Date: 2002-07-26T06:02:40Z
• Authors: Hiroshi Imahori; Hiroyuki Norieda; Yoshinobu Nishimura; Iwao Yamazaki; Kazuo Higuchi; Naohiko Kato; Tomoyoshi Motohiro; Hiroko Yamada; Koichi Tamaki; Masatoshi Arimura; Yoshiteru Sakata
• Keywords: 01 natural sciences; 0104 chemical sciences

Disulfides, with a systematic series of alkyl spacers containing porphyrins at both terminals, were prepared to investigate the effect of the spacer length on the structure and photoelectrochemical properties of self-assembled monolayers (SAMs) of the porphyrins on a gold electrode. The structure of the SAMs was studied using ultraviolet (UV)−visible absorption spectroscopy in transmission mode, cyclic voltammetry, UV−visible ellipsometry, and fluorescence spectroscopy. These measurements showed that as the length of the spacers increases, the SAMs tend to form highly ordered structures on the gold electrodes. In addition, the structures of the monolayers vary depending on the even and odd number of the methylene spacers (n). From these measurements a porphyrin dimer model is proposed in that the two porphyrins take J-aggregate-like partially stacked structures in the monolayers. Photoelectrochemical studies were carried out in argon-saturated Na2SO4 aqueous solution containing methyl viologen as an elect...