Fluorescence and electrochemical integrated dual-signal sensor for the detection of iron ions in water based on an ITO substrate

A novel type of fluorescent and electrochemical dual-signal sensor was constructed for the sensitive and selective detection of iron ions (Fe³⁺) based on a fluorescent material (Chi-FITC-4MU), which was synthesized by combining the organic dye 4-methylumbelliferone (4-MU), chitosan, and fluorescein isothiocyanate (FITC) in a simple step process. The 4-MU could bind to Fe³⁺ to form a complex, and clearly improved the selectivity of Chi-FITC-4MU for Fe³⁺ detection. FITC showed excellent fluorescence performance and chitosan was beneficial to the curing of the material. By solidifying the fluorescent material on an ITO surface, the dual-signal detection of Fe³⁺ could be realized with excellent selectivity, stability, and anti-interference ability. Based on the unique fluorescence properties of this sensor, the concentration of Fe³⁺ could be visualized in the linear range of 0.1-100 μM based on the degree of fluorescence quenching. Moreover, the highly sensitive and rapid analysis of low concentrations of Fe³⁺ was achieved through the electrochemical properties of the ITO sensor. The limit of detection (LOD) and the corresponding linear range were 0.0184 nM and 0.1-500 nM, respectively. Furthermore, this dual-signal sensor was effectively used for the detection of Fe³⁺ in actual water.