Polypyrrole with a functionalized multi-walled carbon nanotube hybrid nanocomposite: a new and efficient nitrite sensor

This study mainly focuses on the electrochemical-assisted synthesis of conducting polymers such as polypyrrole (PPy) with sodium dodecyl sulfate (SDS) as a surfactant and supported with functionalized multi-walled carbon nanotubes (f-MWCNTs). This nanohybrid composite was used as a nitrite sensor in aqueous medium. The co-deposition of f-MWCNTs into the polymer matrix was studied using scanning electron microscopy, atomic force microscopy and impedance analysis methods. The images obtained from the aforementioned techniques clearly revealed the incorporation of f-MWCNTs into the PPy/SDS matrix. The impedance values of the PPy/SDS/f-MWCNT composite films were found to be lower than those of pure PPy/SDS films. It was also observed that the capacitance of the PPy/SDS/f-MWCNT composite was found to be higher than the capacitance of the PPy/SDS composite. In addition, the capacitance of the composites gradually increased with respect to the increasing percentage of f-MWCNTs (from 0.1 to 0.3). The PPy/SDS/f-MWCNT composite-modified GCE exhibited a sensitive response to the electrochemical oxidation of nitrites. Under optimum conditions, the oxidation peak current of nitrites linearly increased with their concentration in the range from 3 M to 1120 M with the system exhibiting a lower detection limit (LOD) of 0.11 M (110 nM) (S/N = 3). This LOD was much lower than the maximum admissible levels of nitrites in drinking water established by the European Community. Thus, the prepared hybrid composite may be a viable alternative as a highly selective sensor for the detection of nitrite ions present in real water bodies.