Abstract:

In the azobenzene-derivative (ABD) LB film deposited on 2-mercaptoethanol monolayer film, the reduction potential of cis-ABD to hydrazobenzene derivative(HBD) is more anodic than the oxidation potential of HBD to trans-ABD. It is because the separation of redox potentials between trans-ABD and HBD is smaller than the separation of reduction potentials between cis-ABD and trans-ABD. Furthermore, a pair of electrical spike currents are observed with the on and off of UV light irradiation in a certain potential region. In this report, we show that the redox rate constants of ABD monolayer film can be estimated by analyzing this electrical Spike current. The redox rate constants at different electrode potentials were calculated in the same way. Plotting log (K₁) against V vs. Ag/AgCl and log(K₂) against V vs. Ag/AgCl, two straight lines followed by Tafel equation are obtained at these potentials. It is concluded from this result that the charge-transfer process control these reaction kinetics.

Key words: photoelectrochemistry, ABD monolayer, Redox rate constants