A Study of the Electrochemical Behavior of Poly [N-Vinyl Carbazole] Formed on Carbon-Fiber Microelectrodes and Its Response to Dopamine

N-vinyl carbazole (NVCz) random polymers were electrochemically coated onto micron-size carbon fibers in lithium perchlorate/acetonitrile $({\hbox {LiClO}}_{4} /{\hbox {ACN}})$ , sodium perchlorate/acetonitrile $({\hbox {NaClO}}_{4} /{\hbox {ACN}})$ , and tetraethylammonium tetrafluoroborate/acetonitrile $({\hbox {TEABF}}_{4} /{\hbox {ACN}})$ solutions in order to form dopamine-sensing layers on the carbon fiber microelectrodes (CFMEs). The resulting micron-thick polymer films were characterized by using scanning electron microscopy and Fourier transform infrared reflectance spectroscopy. Electrocoating of polymeric film was performed by three different electrochemical methods such as cyclic voltammetry and chronoamperometric and chronopotentiometric polarizations. These modified CFMEs were tested against dopamine by applying only cyclovoltammetric techniques. Under optimum experimental conditions, the electrode shows a reversible and stable behavior during 24 days in a 0.1-M ${\hbox {TEABF}}_{4} /{\hbox {ACN}}$ solution and, hence, can be considered as a promising sensor for dopamine detection. The dopamine detection limit as low as 0.01 nM (3S/N) was obtained for the polymer film formed among applied cyclic voltammetry, chronoamperometry, and chronopotentiometry. The polymer film was demonstrated to offer high selectivity toward dopamine detection in the presence of ascorbic acid.