A Recyclable Optical Fiber Sensor Based on Fluorescent Carbon Dots for the Determination of Ferric Ion Concentrations

A new recyclable fiber optic sensor with a carbon dot/cellulose acetate (CA)-sensitive membrane, in which carbon dots prepared by a hydrothermal method were embedded in the CA film matrix, was successfully used for ferric ion detection. The fluorescent carbon dots immobilized in a sensitive CA membrane are effectively quenched by ferric ion in aqueous solution, and the linear relationship between the fluorescent response of the carbon dots and the Fe3+ concentration was described by the Stern-Volmer equation. A lock-in amplifier was used for detecting the Fe3+ concentration in this recyclable fiber optic sensor based on phase-modulation fluorometry. A linear calibration was obtained in the range from 0.1 to 1.0 mM with a detection limit of 0.03 mM (S/N = 3). This carbon dot/CA sensitive membrane can be recycled and used for ferric ion detection with a good linear calibration.