Chitosan-Capped Silver Nanoparticles for the Electrochemical Detection of Congo Red in River Water Samples

Congo red (CR), a synthetic azo dye, is known for its high toxicity and potential to bioaccumulate in the food chain. Exposure to CR-contaminated water can lead to various health issues, including cancer, underscoring the need for effective quantification and treatment methods. While reliable, traditional chromatographic and spectroscopic techniques are often complex, require toxic solvents, and may not be suitable for rapid or on-site analysis. Herein, we report a replacement tool for quantifying CR in water samples using an electrochemical sensor modified with biosynthesized chitosan-capped silver nanoparticles (AgNPs). AgNP identification was accomplished using ultraviolet-visible spectroscopy and square wave voltammetry (SWV), which showed AgNP characteristic peaks at 438 nm and 0.06 V, respectively. A transmission electron microscope confirmed the spherical shape of AgNPs and their average size (30 nm). The electrocatalytic activity of AgNPs towards CR was also approved using cyclic voltammetry, SWV, and impedance spectroscopy. Thus, the SWVs of different concentrations of CR were used to obtain the calibration curve, showing limits of detection and quantification of 0.017 and 0.056 μM, respectively. Additionally, the interferences and real sample studies showed that the chitosan-capped AgNPs sensor is suitable for quantifying CR in river water samples with high selectivity.