Ultrathin Carbon Nanoparticle Composite Film Electrodes: Distinguishing Dopamine and Ascorbate

Abstract

Ultrathin carbon nanoparticle -poly(diallyldimethylammonium chloride) films (CNP-PDDAC films) are formed on tin-doped indium oxide (ITO) electrodes in a layer-by-layer electrostatic deposition process employing 9 -18 nm diameter carbon particles. Transparent and strongly adhering films of high electrical conductivity are formed and characterized in terms of their electrochemical reactivity. When immersed in aqueous 0.1 M phosphate buffer pH 7, each layer of CNP-PDDAC (of ca. 5 -6 nm average thickness) is adding an interfacial capacitance of ca. 10 mF cm À2. Absorption into the CNP -PDDAC nanocomposite film is dominated by the sites in the PDDAC cationomer and therefore anionic molecules such as indigo carmine are strongly bound and retained within the film (cationic binding sites per layer ca. 150 pmol cm À2 ). In contrast, cationic redox systems such as ferrocenylmethyltrimethyl-ammonium þ fail to bind. For solution phase redox systems such as hydroquinone, the rate of electron transfer is dramatically affected by the CNP-PDDAC film and switched from completely irreversible to highly reversible even with a single layer of carbon nanoparticles. For the mixed redox system ascorbate -dopamine in 0.1 M phosphate buffer pH 7 cyclic voltammograms suggest a rapid and selective temporary poisoning process which causes the ascorbate oxidation to be suppressed in the second potential cycle. This effect is exploited for the detection of micromolar concentrations of dopamine in the presence of millimolar ascorbate.

Fabrication, Characterization, and Application of ‘Sandwich‐Type’ Electrode Based on Single‐Walled Carbon Nanotubes and Room Temperature Ionic Liquid

“…These two oxidation peak potentials were both lower, respectively, than those reported [3, 29 -31], suggesting that the overpotentials for the oxidation of DA and AA in the sandwich -type electrode were lower. There was only a pair of redox peaks of DA and the oxidation peak of AA disappeared in successive second cycle (curve b), which was in accordance with the results reported by Amiri et al [30]. In the second cycle the current response of DA also decreased.…”

“Hydrothermal wrapping” with poly(4-vinylpyridine) introduces functionality: pH-sensitive core–shell carbon nanomaterials

“…The charge under the curve once again led to a Langmuir-type curve that plateaued at approximately 3.3 × 10 -4 C (see Figure 4e). This relates to a maximum number of adsorption sites on the CSNP film being approximately 4.1 x 10 15 (assuming a twoelectron process [33]). The oxidation and reduction peak-to-peak separation at low concentrations was approximately 75 mV which increased with increasing concentration to 95 mV.…”

Sensitive Electrochemical Sensor for Determination of Methyldopa Based on Polypyrrole/Carbon Nanoparticle Composite Thin Film Made by In Situ Electropolymerization

“…This rapidly expanding field creates many exciting new composite materials with desirable properties, which are unknown in the parent constituent materials [30][31][32]. The advantages of carbon nanoparticles such as their highly effective surface area, high porosity, more adsorption capability and excellent electrical conductivity make them suitable for improving properties of composite materials for preparation of modified electrodes [33,34].…”