Simple and Efficient Synthesis of Various Sized Gold Nanoparticles for the Selective Electrochemical Determination of Dopamine

Neurotransmitters, the material bases for nerve signaling, play an important role in the physiological activities in the body. Accurate analysis of neurotransmitter concentration is of great significance for disease prevention and control. They are secreted in low concentrations; therefore highly sensitive detection methods are needed. In this paper, 3 spherical gold nanoparticles were prepared with diameters of 5 nm, 20 nm, and 50 nm. The gold nanoparticles were deposited on the surface of carbon fiber microelectrodes by a one-step potentiostatic process to obtain nanogold-modified carbon fiber microelectrodes (AuNPs/CFME). These electrodes were electrochemically characterized before and after modification. The electrochemical properties of dopamine, norepinephrine, ascorbic acid, and potassium ferricyanide were also studied on the microelectrodes before and after modification. The results demonstrated that AuNPs/CFME had an electrocatalytic influence upon catecholamines with positive charges with shielding effects against negatively charged substances. The smaller spherical gold nanoparticles had better catalytic shielding properties. Under the optimum conditions, the differential pulse voltammetry (DPV) peak current and the concentration of dopamine with high concentration of ascorbic acid displayed a linear range of 0.1 mu M to 10 mu M with a detection limit of 0.013 mu M based on a signal-to-noise ratio of 3. This work provides a simple and easy approach to selectively determine positively charged substances and shielding negatively charged compounds. The prepared gold nanoparticles were employed for the selective determination of dopamine in the presence of high concentrations of ascorbic acid in the mouse serum samples with excellent analytical performance. This work shows high selectivity for dopamine, which can be applied to its selective determination in the presence of high concentrations of ascorbic acid in biological systems.