Evaluation of Electrochemically Reduced Gold Nanoparticle-Graphene Nanocomposites for the Determination of Dopamine

Two gold nanoparticle-graphene nanocomposites were electrochemically obtained by the one-step constant potential coreduction of graphene oxide and gold ions or the electrodeposition of gold nanoparticles on graphene oxide followed by electrochemical reduction of graphene oxide. The surface morphology, electron transfer rate, and electrocatalytic activity toward the oxidation of dopamine on these nanocomposites were systematically studied. The results showed that both preparations synthesized gold nanoparticle-graphene nanocomposites. The nanocomposite obtained by the one-step synthesis showed higher electron transfer kinetics and electrocatalytic activity toward dopamine than the material obtained by the two-step synthesis. Consequently, the one-step nanocomposite was used to modify a glassy carbon electrode to form a dopamine sensor. Differential pulse voltammetry was used to detect dopamine with a detection limit of 0.1 micromolar and a linear dynamic range from 0.2 to 20 micromolar. The sensor displayed good stability, high reproducibility, and was used for the determination of dopamine in human urine.