Fabrication and optimization of ZnO-multiwalled carbon nanotubes modified glassy carbon electrode for the detection of 2-(4-(1-isonicotinoyl-5-aryl-4,5-dihydro-1 H -pyrazol-3-yl)phenoxy)- N -arylacetamides

A series of 2-(4-(1-isonicotinoyl-5-aryl-4,5-dihydro-1 H -pyrazol-3-yl)phenoxy)- N -arylacetamides has been synthesized in appreciable yields. The quantitative determination and redox behavior of the synthesized compounds were estimated by cyclic voltammetry (CV). Further, it was observed that nanocomposites have come to be the superior modifying materials for electrochemical sensing. Herein, a highly sophisticated and sensitive zinc oxide (ZnO)-multi walled carbon nanotubes (MWCNTs) composite film modified glassy carbon electrode (GCE) (ZnO-MWCNTs/GCE) was fabricated for its use as the working electrode. Prior to the fabrication, the synthesized ZnO material was characterized by SEM to confirm the successful synthesis. After the fabrication of the ZnO-MWCNTs/GCE sensor, it together with its corresponding forms i.e., ZnO/GCE and MWCNTs/GCE including bare GCE was characterized by voltammetry. The increase in effective surface area of modified GCE from that of unembellished GCE of 0.0314 cm 2 up to 0.081 cm 2 resulted in better electrocatalytic activity in terms of responses of the compounds under investigation. The composite film modified GCE resulted in an excellent sensor for the reported compounds in terms of low potential detection, a low detection limit, fast and clear response. Moreover, the effect of pH, varying scan rates, solvents, electrolytes, concentration, and substituents (in terms of the Hammett equation) have also been analyzed on the CV responses of the modified GCE. The best results were obtained for a pH value corresponding to 5.83 with TEAP as the surfactant at the scan rate of 0.1 V/s. The incorporation of ZnO nanoparticles with multi walled carbon nanotubes (MWCNTs) greatly increases the voltammetric peak current and electrochemical reactivity of the compounds. The electrochemical sensor shows sensitivity par excellence and exhibits a wide detection range varying from 1.0 × 10 –4 to 3.0 × 10 –4 M. Moreover, the detection limit is 1.25 × 10 −6 M with a correlation coefficient ( r 2 ) of 0.994. The studies delineated the diffusion-controlled and irreversible behavior of electrocatalytic reaction for all the compounds under investigation. Graphic Abstract