Modification of flame etched carbon-fiber microelectrode (FE-CFME) by single walled carbon nanotube/pyreneacetic acid (SWCNT/PAA) nanocomposite for sensitive and selective detection of dopamine

Abstract

An inexpensive, simple and fast methode of sensor construction as well as negligible sensor surface fouling, along with the high sensitivity and selectivity has always been a challenge in the fabrication of electrochemical sensors. In this study, to achieve this goal, carbon fiber microelectrode (CFME) was pretreated by applying fast flame etching and then simply modifed by pyrene acetic acid (PAA) decorated single walled carbon nanotube (SWCNT) nanocomposite for highly sensitive and selective dopamine (DA) detection. The results show that, although the CFME became active upon flame etching due to introduces nanometer-scale roughness features on it, surface modification by SWCNT-PAA further increases its sensitivity due to synergistic effects. Attaching PAA onto SWCNTs can effectively inhibit the π-stacking of the SWCNTs to prevent their agglomeration and offer a large surface area of electrode, as well as enhancing the diffusion of positively charged DA by its anionic carboxylate moieties. This is the first report on applying PAA/SWCNT nanocomposite for surface modification of flame etched carbon fiber microelectrode (FE-CFME). The surface morphology of the Bare-CFME, FE-CFME, and FE-CFME/SWCNT-PAA electrodes were evaluated using Field-emission scanning electron microscopy (FE-SEM), being correlated with the electrochemical characteristics observed by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. As expected, the fabricated sensor showed improved electrochemical response with high sensitivity and selectivity. Under optimum conditions, this sensor exhibited high performance toward DA determination with good linearity in a broad linear range of 0.5 to 22 μM with the detection limit of 12.9 nM, and excellent reproducibility and repeatability. The practical applicability of the fabricated sensor has been successfully tested for the determination of DA in human serum and injection ampoule samples with recovery rates ranging from 98 % to 105 % and relative standard deviations below 3.1 %.