Redox and photochemical behaviour of a porphyrin monolayer on an indium-tin oxide electrode

• Published in: Electrochimica acta Vol. 51; no. 4; pp. 677 - 683
• Main Authors: Araki, Naoko, Obata, Makoto, Ichimura, Akio, Amao, Yutaka, Mitsuo, Kazunori, Asai, Keisuke, Yano, Shigenobu
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.11.2005; Elsevier
• Subjects: Adsorption; Chemistry; Cyclic voltammetry; Electrochemistry; Exact sciences and technology; General and physical chemistry; Indium-tin oxide; Oxygen quenching; Photochemistry; Porphyrin monolayer; Study of interfaces; Cyclic voltammetry; Indium-tin oxide; Porphyrin monolayer; Oxygen quenching; Photochemistry; Electrode adsorption; Monolayer; Indium tin oxide electrode; Photoluminescence; Electrode electrolyte interface; Experimental study; Non metal porphyrin; Fluorescence spectrometry; Luminescence decay; Organic solvent; Luminescence quenching; Ultraviolet visible spectrometry
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2005.05.030

In order to investigate photoluminescence behaviour of an ordered molecular porphyrin monolayer and its quenching properties by oxygen gas, a porphyrin with long alkyl chains, 5,10,15,20-tetrakis[4-(11-carboxylundecane-1-oxy)phenyl]porphyrin ( 4), was synthesized and adsorbed onto an indium-tin oxide (ITO) substrate by a chemical dipping method. Cyclic voltammetry was used to analyze the ITO electrode coated with 4. The peak current of the first oxidation was proportional to the sweep rate, and the surface coverage was estimated to be 2.3–2.5 × 10 −10 mol cm −2. The UV–vis spectrum of the monolayer showed a broadened Soret band, which shifted to longer wavelength. These features suggest that the porphyrin moieties of 4 are packed to form a J-type structure. The oxygen quenching ratio of the porphyrin 4 monolayer on the ITO electrode, I 0/ I 100, was estimated to be 1.25, where I 0 and I 100 are, respectively, luminescence intensity values in 100% argon and 100% oxygen. On repeated step cycling between 100% argon and 100% oxygen atmospheres, the response times of luminescence quenching were 10 s (argon to oxygen) and 23 s (oxygen to argon). These findings suggest that a monolayer of sensing dye is applicable for oxygen sensing system without deterioration of size-accuracy of models.