Large surface vanadium pentoxide nanosheet modified screen-printed electrode for nanomolar diclofenac determination

Abstract

This work reports on the utilization of vanadium pentoxide nanosheet (V2O5 NS)-modified screen-printed electrodes (SPEs) for the nanomolar voltammetric determination of diclofenac (DCF). V2O5 NSs were produced with a facile bath sonication method in a blend of 75/25% v/v H2O/isopropyl alcohol. The morphological, structural, and electrochemical characteristics of exfoliated V2O5 NSs were evaluated via scanning electron microscopy, X-ray diffraction, infrared spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). V2O5 NSs showed a 2D low dimensional morphology with most layers having dimensions of a few micrometers. Diagnostics CV studies using 5-hydroxydiclofenac or 2-(2-hydroxyphenyl) acetic acid, which have been proposed in literature to be involved in the electro oxidation of DCF, suggested that the actual mechanism is more complicated and need to be further elucidated. CV and EIS data demonstrated that at pH>6 V2O5 NSs deprived of their characteristic pseudocapacitive properties offering low background signals and enhanced electrocatalytic properties toward DCF. Among different preconcentration treatments examined, a short (192 s) cyclic potentiodynamic treatment was found to exhibit a stable, semi reversible pair of peaks of increased magnitude with successive cycles, and low background signal. The quantification of DCF was conducted using differential pulse voltammetry. A well-defined oxidation peak at ca. 380 mV at pH 7 vs. Ag/AgCl/3 M KCl was recorded and its height was found to be linearly correlated with the concentration of DCF over the range 20–200 nmol L−1, while a limit of detection (3Sx/slope) of 3.1 nmol L−1 was achieved. The response of V2O5 NS/SPE was evaluated against common interfering compounds, while the accuracy of the method was evaluated in spiked tap water samples.