Adsorption investigation of two surfactants at solid/aqueous interface by a cyclic voltammetry method

In this paper, cyclic voltammetry (CV) was proposed as a convenient tool for monitoring the adsorption of surfactant at solid/aqueous interface and two cationic surfactants were studied. The adsorption of cetyl trimethylammonium bromide (CTAB) on Indium tin oxide glass (ITO) in different concentration aqueous solution was investigated and the calculated thickness indicates the changes of morphology of adsorbed layer. Experimental results showed that high electrolyte concentration made the adsorbed layer dense and thinner. Ethanediyl-α,β-bis(cetyldimethylammonium bromide), referred to as dimeric 16-2-16 surfactant (where 16 and 2 are the carbon numbers of the side alkyl chains and of the alkanediyl spacer) was also studied. The electrical properties of adsorbed layer of the surfactant 16-2-16 on ITO were also analyzed and the related morphology of adsorbed layer was discussed. Cyclic voltammetry proves to be a technology that can monitor the electrical properties of surfactant adsorbed layer in various concentrations even below cmc.