Graphene/MWCNT/copper-nanoparticle fabricated printed electrode for diclofenac detection in milk and drinking water: Electrochemical and in-silico analysis

• A novel printed electrode fabricated with graphene/MWCNT/copper nanoparticles and oleic acid (Graphene-MWCNT-CuNP@OA) demonstrates excellent electrochemical sensing performance for diclofenac sodium detection. • Quantum chemical calculations (DFT) were employed to investigate the interaction between the Graphene-MWCNT-CuNP@OA composite and diclofenac, revealing insights into binding interactions and electronic properties at the nanoscale. • The developed sensor exhibits high sensitivity with a low detection limit of 57.7 nM and a wide linear range of 17.41 μM to 206.45 μM for diclofenac detection. • The applicability of the sensor for real-world samples was validated through successful diclofenac detection in spiked milk and drinking water samples. This study investigates the electrochemical sensing of Diclofenac sodium. A single carbon printed electrode was modified with the combination of graphene (GRP), multi-walled carbon nanotube (MWCNT), and copper-nanoparticle (CuNP) blended with oleic acid (OA) (i.e. CuNP@OA) as working electrode material of the three-electrode system (i.e. GRP-MWCNT-CuNP@OA). Here, copper nanoparticles, being responsible for catalysis, are embedded on the matrix comprising of GRP and MWCNT which serves as the conductive matrix material for electrode. The OA acts as a stabilising agent for the active CuNPs. The chemical sensitivity feature (in terms of binding interaction) of the GRP-MWCNT-CuNP@OA composite model interacting with the Diclofenac has been examined by implementing quantum chemical calculation approaches like molecular modelling, semi-empirical, QTAIM, and NCI-plot based tools. Some useful and important properties have also been examined using electronic parameters such as HOMO, LUMO, HOMO-LUMO gap, charge transfer (CT), QTAIM-based topological parameters, etc. which could indeed be helpful for the experimentalists in understanding the structural, stability/energetics, and electronic features of the probed composite models at nano-level. Further, the characterization of the composite was carried out through some sophisticated characterization techniques like scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and powder XRD. Cyclic voltammetry (CV) is used for studying stability of the composite and chemical kinetics of the oxidation of Diclofenac sodium. Differential pulse voltammetry (DPV) was used to evaluate the sensing performance of the above-mentioned material by determining the lower range detection limit of Diclofenac (57.7 nM) and linear range (17.41 μM – 206.45 μM) of the electrochemical sensor. Further to validate the results obtained, real sample analysis was performed using the developed electrode in drinking water and milk spiked with Diclofenac.