The modification of graphite electrode surfaces with different hardness using hexane/CTAB-CTAmodified-butanol/water microemulsion forming system with inverse micelles (W/O) is presented. CTAB is modified by exchanging bromide ions of the surfactant with ferrocyanide ions in a salt solution. Carbon electrodes are modified by immersing them into a W/O microemulsion, followed by a rinsing step with pure water, and a potential cycling in a ferrocyanide solution. After this treatment, electrodes display two redox peaks, characteristic of strongly adsorbed species. The amount of adsorbed material at the electrode surface is greater for soft graphite electrodes than for hard ones. FTIR spectra of carbon electrodes before and after modification not show signal of C-C bonds and the increase of C-N signal from ferrocyanide ions attached to the surfactant. These results support the formation of a new bond between the surfactants tail and the carbon surface.
In this paper a voltammetric study of a three-phase system modified with the surfactant CTAB in a liquid/liquid interface is presented. The three-phase system consists of a nitrobenzene microdroplet (1µL) with 0.1 M ferrocene, immobilized in a paraffin impregnated graphite electrode and immersed in a LiClO 4 solution. Surfactant molecules present at the interface increase the ClO 4¯ ion transfer resistance at low concentrations, and the ferrocenium ion transfer at high concentrations. A current mapping of the ClO 4¯ ions around a nitrobenzene microdroplet using SECM is included. SECM results demonstrate that ionic transport takes place at the three-phase region, according to data published in the literature. Experimental data simulations using the finite element method qualitatively describe the system.
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