Electrodeposition of Pt–Ru nanoparticles on multi-walled carbon nanotubes: Application in sensitive voltammetric determination of methyldopa

Abstract

A modified glassy carbon electrode, prepared by potentiostatic electrodeposition of platinum–ruthenium nanoparticles (Pt–RuNPs) onto a multi-walled carbon nanotube (MWCNT) layer, offers dramatic improvements in the stability and sensitivity of voltammetric responses toward methyldopa (m-dopa) compared to glassy carbon electrodes individually coated with MWCNT or Pt–RuNPs. The surface morphology and nature of the hybrid film (Pt–RuNPs/MWCNT) deposited on glassy carbon electrodes was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. A remarkable enhancement in the microscopic area of the electrode together with the catalytic role of the composite modifier resulted in a considerable increase in the peak current (110 times) and a negative shift (−200 mV) in the oxidation peak potential of m-dopa. The mechanism of the electrocatalytic process on the surface of the modified electrode was analyzed via cyclic voltammograms at various potential sweep rates and pHs of the buffer solutions. Differential pulse voltammetry was applied and shown to provide a very sensitive analytical method for the determination of sub-micromolar amounts of m-dopa, for which a linear dynamic range of 0.05–40 μM and a detection limit of 10 nM was obtained. The modified electrode was successfully used for accurate determination of trace amounts of m-dopa in pharmaceutical and clinical preparations.