A bimetallic CuFe layered double hydroxide supported on carbon black: An efficient and sustainable electrocatalyst for the electrochemical detection of ornidazole

Layered double hydroxide (LDH) materials have emerged as promising earth-abundant and cost-effective materials in a range of applications. Herein, a CuFe-LDH was synthesised using a hydrothermal reaction and supported by non-covalently functionalised carbon black (CB) to form a highly efficient electrochemical sensor (CuFe/CB) for the antimicrobial drug ornidazole. The CuFe-LDH and non-covalently functionalised CB were characterised using XPS, XRD and FE-SEM. On functionalising the pristine CB with tannic acid, discrete CB particles, that exhibited more crystalline features, became evident. By decorating the CB particles with the CuFe-LDH, a more compact surface was produced with the flakes of the CuFe-LDH filling the spaces between the CB particles. The CuFe/CB composite facilitated the electrochemical reduction of ornidazole, with a more thermodynamically favoured reduction potential of –0.586 V vs Ag/AgCl compared to the individual components or unmodified glassy carbon. Using differential pulse voltammetry, a linear calibration curve, extending to low concentrations of 10 nM was obtained with a sensitivity of 0.8712 µA µM –1 cm –2 and a limit of detection of 7.5 nM. Very good selectivity was seen in the presence of several other antimicrobial drugs, and in the presence of a variety of inorganic ions commonly found in aquatic systems. Very good recovery was achieved in both tap and canal/river water samples, ranging from 96.7 % to 102.0 % for the more complex canal/river water. • A sustainable sensor was formed with a Cu and Fe layered double hydroxide and carbon black. • The sensor was employed to detect ornidazole, a drug found in aquatic systems. • Detection in the nM region with excellent selectivity and sensitivity was achieved.