Département de chimie moléculaire

The authors report the characterization of a dispersion of multi-wall carbon nanotubes (CNT) in a soln. of polyethylenimine (PEI) functionalized with dopamine (Do), the electrochem. behavior of glassy carbon electrodes (GCE) modified with the resulting dispersion, and its anal. application for the highly sensitive quantification of NADH without fouling of the surface. The dispersion was obtained by sonicating for 60 min 1.0 mg CNT in 1.0 mL of 1.0 mg/mL PEI-Do soln. prepd. in 50/50 (vol./vol.) ethanol/water. The presence of Do covalently bonded to PEI promotes hydrophobic $π$ interactions with the CNT walls and improves significantly the dispersability of CNT in this mixt. The dispersion is highly stable since after 2 mo resting at room temp. no phase sepn. was obsd. This dispersion was drop-coated over GCE, and after solvent evapn., a very reproducible and uniform coverage was obtained. An electrochem. pretreatment (activation) of such a modified GCE electrode allowed the sensitive quantification of NADH at potentials ≥-0.025 V The response of NADH at the electrochem. activated GCE modified with the dispersion of CNT in PEI-Do soln. (GCE/CNT-PEI-Do), demonstrated to be highly reproducible. The relative std. deviation for the NADH sensitivity obtained with 15 electrodes and 3 different dispersions was 8.9{%}. Even more important, after 10 calibrations for NADH with the same surface the decrease in the sensitivity was smaller than 10{%}. The dispersion was characterized by Field Emission SEM (FE-SEM), FTIR Spectroscopy (FTIR) while the electrodes modified with the dispersion were evaluated using different electrochem. techniques (Cyclic voltammetry (CV), Amperometry and Electrochem. Impedance Spectroscopy (EIS)). [on SciFinder(R)]