Functionalized Single‐Walled Carbon Nanotubes Modified Microsensors for the Selective Response of Epinephrine in Presence of Ascorbic Acid

Abstract

Modified stainless steel microelectrodes (microwire diameter: 300 mm) were assembled using functionalized singlewalled carbon nanotubes (SWCNTs) deposited by the EPD method (electrophoretical deposition process). The functionalized SWCNTs, which covered the microelectrode surfaces, showed an improved sensitivity and selectivity toward the electrochemical detection of epinephrine. These chemical sensors hampered the voltammetric responses of ascorbic acid (AA) and uric acid (UA), while the electrochemical oxidation of epinephrine was significantly enhanced. Using the differential pulse voltammetry (DPV) technique, epinephrine showed a very well resolved peak centered around 240 mV, while 1 mM of AA (present in the same solution) was not detected. The corresponding permeability and permselectivity parameters were also evaluated for ascorbic acid and uric acid. To investigate the sensor selectivity, a comparative study performed using microsensors assembled with non functionalized carbon nanotubes, deposited on the microelectrode surfaces by a chemical vapor deposition (CVD) technique, was also carried out. This study was useful to highlight that the presence, or the absence of electrostatic barriers on SWCNTs walls (due to the presence of some chemical functional groups), can be able to control the electrochemical response of these sensors. This optimization resulted in microsensors with a good linear range (2 -100 mM) epinephrine; a good sensitivity (28.1 A M À1 cm À2 ) and interelectrodes reproducibility (RSD% ¼ 7.0, n ¼ 6), a detection of limit (LOD ¼ 3s) of 2 mM; a response time of 6 s; a significant operational stability (of 13 hours in continuous working conditions) and long term stability (1 month).

Review: Carbon nanotube based electrochemical sensors for biomolecules

“…Because of their similar structures, epinephrine and norepinephrine are difficult to distinguish electrochemically. Valentini et al have detected epinephrine at a stainless steel wire coated with SWCNT by electrodeposition [61]. This electrode is smaller than most, 300 m in diameter, but the 2 M detection limits are high for physiological studies.…”

Efficient Electrocatalytic Detection of Epinephrine at Gold Electrodes Modified with Self‐Assembled Metallo‐Octacarboxyphthalocyanine Complexes

“…The epinephrine electrooxidation at bare electrode is associated with problems of slow electron transfer rate and adsorptions of epinephrine on the electrode surfaces leading to passivation [20]. Electrochemical methods for epinephrine analysis making use of modified carbon electrodes [14 -19], carbon nanotubes [20,21] and gold nanoparticles modified electrodes [14,22,23] have been reported. The major challenge in epinephrine analysis is the elimination of interferences from ascorbic acid; ascorbic acid oxidation peak is very close to that of epinephrine which often results to their peaks overlapping.…”

Gold Nanoparticles/Carbon Nanotubes Composite Film Modified Glassy Carbon Electrode Determination of Meclofenoxate Hydrochloride

“…Afterwards, the electrode was immersed in the aqueous suspension and connected as the positive pole whereas a platinum electrode was used as the negative pole. A potential of 10 V was applied for 30s electrophoretic accumulation of SWNTs [15]. After that, it could be seen the GCE was covered with a blue-color thin film.…”

“…A multi-potential steps was employed for the direct electrodeposition of metal particles. In a first series of experiments, a pulse potential profile of 200 mV (500 ms) ~ -1200 mV (100 ms) ~200 mV (500 ms) (vs. Ag/AgCl) was applied and 30 pulses were used for each deposition [15]. At the end of process, the modified electrode was thoroughly washed with pure water.…”