A novel graphene quantum dots/choline chloride/gold nanoparticles-modified carbon fiber microelectrode for sensitive and selective determination of dopamine in the presence of a high concentration of ascorbic acid

We prepared a three-layer composite of gold nanoparticles (AuNPs), choline (Ch) and graphene quantum dots (GQDs), and applied it to modify a carbon fiber microelectrode (CFME) by potentiostatic deposition to obtain a GQDs/Ch/AuNPs/CFME for high-sensitivity determination of dopamine (DA) without inference from ascorbic acid (AA). The surface morphology of electrodes was investigated by scanning electron microscopy. The electrochemical behavior of DA and AA at different modified electrodes was investigated by cyclic voltammetry and differential pulse voltammetry in Tris-HCl buffer (pH = 9.0). Owing to a synergistic effect, the GQDs/ Ch/AuNPs/CFME exhibited an obvious electrocatalytic effect on positively charged DA and a significant shielding effect on negatively charged AA. The influence of experimental variables (duration of modification, pH of the working solution, scan rate) was studied. Under optimum conditions, in the presence of AA (1.0 x 10-3 mol/L), the GQDs/Ch/AuNPs/CFME described a fine linear enhancement for DA oxidation in the concentration range 0.01-10.0 mu M with an estimated lower limit of detection of 1.616 nM and limit of quantification of 5.389 nM. The modified electrochemical sensor was applied for DA determination in the presence of high concentration of AA in mouse serum without separation steps and with good recovery.