A Novel Chitosan-Based Fluorescence Chemosensor for Selective Detection of Fe (III) Ion in Acetic Aqueous Medium

An ecofriendly chitosan-based urolithin fluorescence (Uro-m-Ch) optical sensor was successfully synthesized and characterized by Fourier transform infrared spectroscopy. According to the FTIR results, the chitosan characteristic peaks were observed around 3500−3300 cm−1, 1656 cm−1, 1587 cm−1 and 1179 cm–1 which are attributed to hydroxyl, amide I, N–H deformation and C–O–C stretching, respectively. The Uro-m-Ch featured the representative peaks of chitosan and the lactone carbonyl stretching of the urolithin. The Uro-m-Ch demonstrated fluorescence character in the presence of 1% (v/v) CH3COOH/H2O solution with a maximum excitation wavelength (λmax) within 290–330 nm and λmax emission spectrum at 430 nm with Stokes shift of 100 nm without the target metal ion. Notably, in the presence of iron (III) concentration from 0.10 to 0.080 mM; Uro-m-Ch exhibited a maximum wavelength emission at 420 nm with a decreasing trend in fluorescence intensity. During the selectivity and interference studies, Uro-m-Ch demonstrated a remarkable quenching effect only with Fe3+ ion among various mono- and multivalent metal ions. Considering the fluorescence responses of the Uro-m-Ch, its sensing mechanism towards Fe3+ ion was attributed to intramolecular energy/electron transfer between the lactone group of the urolithin and/or the hydroxyl moiety of the chitosan backbone and the iron (III) ion. Results herein confirmed that Uro-m-Ch is rapid, selective and sensitive towards Fe3+ ion detection in aqueous acetic solution. Keywords: Chitosan, Urolithin B, Iron (III) ion, Fluorescent, Chemosensor, Selective detection