Electrochemical-Assisted Encapsulation of Catechol on a Multiwalled Carbon Nanotube Modified Electrode

Abstract

Electrochemical-assisted encapsulation of a neurotransmitter, catechol (CA), as nanoaggregates on a multiwalled carbon nanotube (>90% of carbon basis MWNT) modified gold electrode (Au/CA@CNT) has been demonstrated without any derivatization or electrode preactivation procedures. Characterization of the CA@CNT by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared atteuated total reflection (FTIR/ATR) spectroscopy, and cyclic voltammetry (CV) collectively revealed stable encapsulation of the CA within strained and misalignment areas of the MWNT capsule. The Au/CA@CNT shows a couple of redox peaks centered at 0 (A1/C1) and 200 mV vs Ag/AgCl (A2/C2) due to the encapsulated (chemisorbed) and physisorbed CA moieties, respectively. The calculated chemisorbed catechol surface excess, Γ_CA, value was 98.3 × 10⁻¹⁰ mol·cm⁻². Control solution phase preparations of CA@CNTs yielded poor loading and instability problems, if it is chemically modified on the gold electrode. Electrochemical mediated oxidation of hydrazine on the Au/CA@CNT was demonstrated with an ∼20 times increase in peak current and 200 mV reduction in the overpotential values in a pH 7 phosphate buffer solution.