Electrochemical, in situ spectrocyclic voltammetric and electrochromic studies of phenosafranine in Nafion_^® film

Abstract

The standard Gibbs energy of hydrophobic interaction of phenosafranine (PS⁺) dye with Nafion^® film (δG_h°) was estimated as -21.17 ± 0.04 kJ mol^-1. The positive and negative scans of PS⁺ in Nafion^® film showed markedly different electrochemical behavior. The apparent diffusion coefficient D_app^red calculated for the reduced PS⁺ (PSH₂⁺) was higher than that of the PS⁺ (D_app^ox) in Nafion^® film, explained by the greater interaction of PS⁺ with the hydrophobic region of the Nafion^® film than the PSH₂⁺. Addition of 2-propanol to the supporting electrolyte (0.5 M H₂SO₄) led to the release of PS⁺ from the electrochemically inactive to the electrochemically active regions of the Nafion^® film. In the in situ spectrocyclic voltammetry study of PS⁺ in Nafion^® film, the formation of leuco dye (PSH₂⁺) was observed during the reduction of PS⁺. The formation of monomer PS⁺ and dimer (PS⁺)₂ was also observed in the in situ spectral study during the oxidation of PSH₂⁺ in Nafion^® film aside from its electrochromic behavior.