Chitosan-based fluorescent probe for the detection of Fe in real water and food samples.

Iron ions play a crucial role in the environment and the human body. Therefore, developing an effective detection method is crucial. In this paper, we report CNS2, a chitosan-based fluorescent probe utilizing naphthalimide as a fluorophore. CNS2 is designed to "quench" its own yellow fluorescence through the specific binding of compounds containing enol structures to Fe. Studying the fluorescence lifetime of CNS2 in the presence or absence of Fe reveals that the quenching mechanism is static. The presence of multiple recognition sites on the chitosan chain bound to Fe gave CNS2 rapid recognition (1 min) and high sensitivity, with a detection limit as low as 0.211 μM. Moreover, the recognition of Fe by CNS2 had a good specificity and was not affected by interferences. More importantly, in this study, CNS2 was successfully utilised to prepare fluorescent composite membranes and to detect Fe in real water samples and a variety of food samples. The results show that the complex sample environment still does not affect the recognition of Fe by CNS2. All the above experiments obtained more satisfactory results, which provide strong support for the detection of Fe by the probe CNS2 in practical applications.