Electrochemistry and photocurrents of the tris(bipyridine)ruthenium(II) and methyl viologen cations immobilized in carrageenan hydrogel

• Published in: Inorganic chemistry 1991-11, Vol.30 (23), p.4421-4425
• Main Authors: Rillema, D. Paul, Edwards, A. Kirk, Perine, Sherry C, Crumbliss, Alvin L
• Format: Article
• Language: English
• Subjects: 400400 - Electrochemistry; 400500 - Photochemistry; AMINES; AZINES; BIPYRIDINES; CHEMICAL PREPARATION; CHEMICAL REACTION KINETICS; CHEMICAL REACTIONS; CHEMISTRY; COMPLEXES; CURRENTS; DECOMPOSITION; ELECTRIC CURRENTS; ELECTROCHEMISTRY; ELECTRODES; EVALUATION; Exact sciences and technology; General and physical chemistry; HETEROCYCLIC COMPOUNDS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; KINETICS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; OXIDATION; PHOTOCHEMICAL REACTIONS; PHOTOCHEMISTRY; PHOTOCURRENTS; PHOTOELECTRIC EFFECT; Photoelectrochemistry. Electrochemiluminescence; PHOTOELECTROMAGNETIC EFFECTS; PHOTOLYSIS; PYRIDINES; REACTION KINETICS; REDUCTION; RUTHENIUM COMPLEXES; SURFACE PROPERTIES; SYNTHESIS; TRANSITION ELEMENT COMPLEXES
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic00023a026

A procedure for immobilization of both a photochromophore, tris(2,2{prime}-bipyridine)ruthenium(II) (Ru(bpy){sub 3}{sup 2+}), and a quencher, methyl viologen (MV{sup 2+}), within a carrageenan hydrogel matrix at an electrode surface is described. Ru(bpy){sub 3}{sup 2+} and MV{sup 2+} exhibited diffusion coefficients that ranged from 10{sup {minus} 7} to 10{sup {minus} 6} cm{sup 2}/s in the hydrogel, which represents an improvement over other immobilization matrices. Photolysis of the resulting hydrogel surface modified electrodes gave rise to a significant photocurrent which depended on the concentrations of Ru(bpy){sub 3}{sup 2+}, MV{sup 2+}, and triethanolamine and resulted in a maximum value of 12 {mu}A/cm{sup 2} after the hydrogel was cured with a solution containing 5 mM Ru(bpy){sub 3}{sup 2+} and 50 mM MV{sup 2+}. The photocurrent was the result of reoxidation of MV{sup +} at the electrode surface following reduction of MV{sup 2+} by photoexcited Ru(bpy){sub 3}{sup 2+}. The quenching rate constant of Ru(bpy){sub 3}{sup 2+} by MV{sup 2+} in the hydrogel was 4.2 {times} 10{sup 8} M{sup {minus}1} s{sup {minus}1}. The photocurrent action spectrum was consistent with Ru(bpy){sub 3}{sup 2+} acting as the photochromophore. Offsetting the potential of the hydrogel electrode verified the role of the MV{sup 2+}/{sup +} redox couple as the source of the current.