Functionalized MWCNT-Au nanoparticles composite as sensing platform for the electrochemical detection of diclofenac at neutral pH

MWCNT-based materials and derived composites with AuNPs were investigated as GCE modifiers for the indirect electrochemical detection of DCF. The morphology and surface chemistry, paying special attention to the influence of the type and distribution of oxygen functional groups on the electrochemical performance of the sensor, were assessed. The higher content and more homogeneous distribution of AuNPs were revealed on the surface of CNTs-COOH compared to CNTs-OH. The detection of DCF was performed at neutral pH being beneficial for real sample analysis. Enhanced sensor performance for DCF recorded on GCE/CNTs-COOH-AuNPs resulted in a low LOD = 185 nM, a wide LR = 0.3–120 µM and appropriate long-term behavior. Moreover, good recoveries of the proposed sensor were validated by testing tap water samples. These results, explained by the excellent characteristics of CNTs-COOH-AuNPs as active electrode materials, represent a significant step forward in the development of sensors for detecting small amounts of analytes in wastewater samples.