Electrokinetic Behavior of Multiwalled Carbon Nanotubes/Poly‐l‐lysine Modified Electrodes in Sodium Dodecylsulfate Bicontinuous Microemulsions

ABSTRACT This work demonstrates for the first time the application of multiwalled carbon nanotubes/poly‐l‐lysine modified pyrolytic graphite electrodes (MWCNTs/PLL/PGE) in sodium dodecylsulfate bicontinuous (SDS BC) microemulsions. Cyclic voltammetric studies of ruthenium(III)hexaamine electroactive probe in these media on both plain and modified pyrolytic graphite electrodes (PGE) mainly gave one peak for each of the cathodic and anodic scans. These reduction–oxidation responses were attributed to [Ru(NH3)6]2+/[Ru(NH3)6]3+ redox couple. In SDS BC microemulsions, the midpoint potentials were found to be −0.22 V for PGE plain and −0.24 V for MWCNTs/PLL/PGE versus saturated calomel electrode. The average peak separations for PGE plain and MWCNTs/PLL/PGE were found to be ∼0.05 and ∼0.04 V between the scan rates of 0.01 and 0.1 V/s, whereas their diffusion coefficients were 1.0 × 10−6 and 7.0 × 10−6 cm2/s, respectively. The rates of electron transfer constants were also found to be 1.47 × 10−1 cm/s for PGE plain and 7.38 × 10−1 cm/s for MWCNTs/PLL/PGE. These enhanced responses were attributed to possible increased surface area of the modified electrode, good distribution of nanotubes within the poly‐l‐lysine matrix, and increased porosity within the MWCNTs/PLL/PGE composite making the nanotubes fully accessible to the electroactive probe. Overly these observations in microemulsions are similar to those observed in phosphate buffer solutions, pH 6.5. Moreover, this study shows a possible application of microemulsions in electroanalysis where simultaneous analysis of both organic and inorganic pollutants in environmental samples is required.