Sustainable Synthesis of Rare Earth Metal Tungstates (REWO, RE = Ce, SM, Gd) for Electrochemical Detection of 4-Nitrotoluene

In this study, the synthesis and application of rare earth tungstates Ce₄W₉O₃₃ (CeW), Sm₂(WO₄)₃ (SmW), and Gd₂(WO₄)₃ (GdW) for the electrochemical detection of 4-nitrotoluene were investigated. The nanoparticles were synthesized using a deep eutectic solvent (DES)-assisted solvothermal method, a technique known for its precision and reproducibility. It resulted in materials with high thermal stability, excellent catalytic activity, and enhanced electronic properties. The synthesized CeW, SmW, and GdW were employed to modify screen-printed carbon electrodes (SPCEs), a widely used and well-established method in the field, which were then characterized using various techniques. Electrochemical performance was evaluated through cyclic voltammetry, differential pulse voltammetry, and amperometric (i-t) responses, all of which are standard methods in electrochemical analysis. The modified electrodes exhibited superior electrochemical behavior compared to bare SPCEs, with CeW/SPCE showing the highest reduction peak current for 4-nitrotoluene detection. The linear range for detection was found to be for DPV= 0.01–576 μM and for i-t = 0.001–306 μM, with a limit of detection of DPV = 0.034 μM and i-t = 0.012 μM. The sensors demonstrated excellent selectivity, reproducibility, and stability, with minimal interference from other substances commonly found in environmental samples. Real-world applicability was confirmed by testing the modified electrodes in the river and tap water samples spiked with 4-nitrotoluene. The CeW/SPCE sensor showed rapid and sensitive response in both matrices, highlighting its potential for environmental monitoring. The robust performance of CeW, SmW, and GdW-modified electrodes underscores their suitability for practical applications in detecting nitrophenols, contributing to effective environmental monitoring and pollution control. This research has the potential to inspire further advancements in the field of electrochemical detection and environmental monitoring.