Electrochemistry and Photocurrents of the Tris(bipyridine)ruthenium(II) and Methyl Viologen Cations Immobilized in Carrageenan Hydrogel
A procedure for immobilization of both a photochromophore, tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+), and a quencher, methyl viologen (MV2+), within a carrageenan hydrogel matrix at an electrode surface is described. Ru(bpy)32+ and MV2+ exhibited diffusion coefficients that ranged from 10-7 to 10-6 cm2/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)32+, MV2+, and triethanolamine and resulted in a maximum value of 12 μA/cm2 after the hydrogel was cured with a solution containing 5 mM Ru(bpy)32+ and 50 mM MV2+. The photocurrent was the result of reoxidation of MV+ at the electrode surface following reduction of MV2+ by photoexcited Ru(bpy)32+. The quenching rate constant of Ru(bpy)32+* by MV2+ in the hydrogel was 4.2 X 108 M-1 s-1. The photocurrent action spectrum was consistent with Ru(bpy)32+ acting as the photochromophore. Offsetting the potential of the hydrogel electrode verified the role of the MV2+/+ redox couple as the source of the current. © 1991, American Chemical Society. All rights reserved.
Rillema, DP; Edwards, AK; Perine, SC; Crumbliss, AL
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