Complex Electrochemical Behavior of Crystal Violet in Aqueous Solution in the Presence of Triton X-100

Abstract

The electrochemical behavior of aqueous crystal violet in the presence of a nonionic surfactant, Triton X-100 (TX-100), was investigated using cyclic voltammetry. The cyclic voltammogram of crystal violet at a platinum electrode in an aqueous solution using 0.16 M NaCl as the supporting electrolyte was very sensitive to solution pH. In the pH range of 1.76 to 2.29, a well-defined voltammogram with one cathodic reduction peak and one anodic oxidation peak indicates unusual electrochemical reactions of crystal violet to yield the diquinoid of N,N,N’,N’-tetramethyl benzidine (TMBOx) upon oxidation, which is reduced through a two-electron process to N,N,N’,N’-tetramethyl benzidine (TMB). The cyclic voltammetric behavior of crystal violet in the presence of TX-100 surfactant, both below and above the critical micelle concentration, depends on the dissolved states of the surfactant. The electrochemical properties of crystal violet have been found to be diffusion controlled and dependent on TX-100 concentration. The electrochemical reaction is coupled with a preceding and a following chemical reaction and follows a CEC (chemical-electrochemical-chemical) mechanism. Interestingly, the unusual electrochemical reaction also occurs in the micellar system, and overall electrochemical behavior is dictated by the structure of crystal violet depending on the solution pH as well as the dissolved state of the surfactant. The findings of the present study may be useful to understand the host-guest chemistry of crystal violet and TX-100 at the molecular level.