Electrochemical adsorption and covalent attachment of erythrosin to modified tin dioxide electrodes and measurement of the photocurrent sensitization to visible wavelength light

Erythrosin (2,4,5,7-tetraiodofluorescein) has been attached to SnO₂ electrode surfaces either through electrochemical adsorption or covalent attachment. SnO₂ electrodes modified with mercaptopropyltrimethoxysilane, 3-(2-aminoethyl)propyltriethoxysilane, or γ-aminopropyltrimethoxysilane showed a considerable enhancement of the currents passed during oxidation of erythrosin and a deposition of several monolayers of active chromophore. Erythrosin was covalently attached to the silane-modified SnO₂ surfaces by means of an amide bond or by the formation of a thiol bond. Small surface concentrations of the adsorbed and covalently attached dye were easily detected by monitoring the I(3d_3/2,5/2) x-ray photoelectron transitions. Sensitization of the SnO₂ current/voltage response to visible wavelength light was observed for both the adsorbed and covalently attached dye electrodes. Enhanced stability and efficiency of the photocurrent response was observed for the covalently attached vs. adsorbed dye molecules.