Multiwalled Carbon Nanotube/Fe-Doped ZnO-Based Sensors for Droplet Electrochemical Detection and Degradation Monitoring of Brilliant Green

The present research work aims to contribute toward the sustainable development goal of water cleanliness by monitoring and removing toxic effluents from wastewater. Herein, we present an electrochemical sensing platform made of a glassy carbon electrode modified with Fe-doped ZnO nanoparticles (NPs) and multiwalled carbon nanotubes (MWCNTs) for the detection of brilliant green (BG) using a smart droplet analysis approach. The Fe-ZnO NPs were synthesized via a hydrothermal method and characterized by various analytical techniques such as UV-visible spectroscopy, XRD, SEM, EDX, and FTIR spectroscopy. Fe-ZnO NPs were found to act as a mediator between the transducer and BG for efficient electron transport, while MWCNTs led to the enhanced current response of BG at the electrode surface owing to their conductive and adsorptive characteristics. Under optimized conditions of pH 6, 0.1 V deposition potential, and 40 s deposition time, a 0.40 nM limit of detection was achieved at the designed nanosensor. Photocatalytic degradation of the dye with NPs was also investigated in different pH media using UV-visible spectroscopy. The dye was found to photocatalytically degrade up to 99% in just 30 min, following first-order kinetics with a rate constant of 0.14 min^-1. The photocatalytic degradation was also monitored electrochemically at the designed sensing platform, and the findings were found to be in good agreement with the results of UV-visible spectroscopy. The developed electrochemical droplet analysis approach is not only economical but also efficient, ultra-sensitive, and environmentally friendly.