Multi-Walled Carbon Nanotubes and Copper Oxide Nanoparticles Composite Used as Transducer Medias in Nitrate Ion-Selective Electrodes

To improve the performance of nitrate solid contact ion-selective electrodes, their design was modified with a composite material consisting of multi-walled carbon nanotubes and copper oxide nanoparticles. The nanocomposite was used in the electrodes as a component of the ion-sensitive membrane (GCE/NC+ISM) and as a solid contact material applied by drop casting (GCE/NC/ISM). A series of comparative studies were conducted to determine which type of modification more favorably affected the performance of each electrode. A classical glassy carbon electrode with a membrane without a nanocomposite was used as a control electrode. The best electrode turned out to be the one in which transducer media in the form of a composite was implemented into the membrane. For the GCE/NC+ISM electrode, the highest sensitivity of 60.41 mV/decade, the lowest detection limit of 5.13 × 10 −7 M, and the widest linearity range of 1 × 10 −6 –1 × 10 −1 M were obtained. The presence of the nanocomposite in the membrane contributed to a significant improvement in electrical performance relative to the unmodified electrode, which in turn resulted in obtaining good potential reversibility and low potential drift—0.085 μV s −1 . The prepared electrode was used to determine the concentration of nitrates in environmental water samples.