Characterization of a fluorescent hydrogel synthesized using chitosan, polyvinyl alcohol and 9-anthraldehyde for the selective detection and discrimination of trace Fe3+ and Fe2+ in water for live-cell imaging

Abstract A three-dimensional fluorescent hydrogel based on chitosan, polyvinyl alcohol and 9-anthraldehyde (ChPA) has been successfully designed and synthesized for the selective detection and discrimination of Fe 3+ and Fe 2+ in aqueous environment. The unique characteristics of ChPA has been confirmed by the Fourier-transform infrared spectroscopy (FTIR), rheological measurement, scanning electron microscopy (SEM), thermogravimetry and differential thermogravimetry (TG-DTG), ultraviolet–visible spectroscopy (UV–vis), fluorescence studies, transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD) and dynamic light scattering (DLS). The emission intensity at 516 nm of the hydrogel has been enhanced remarkably with the addition of Fe 3+ due to the inhibition of the photoinduced electron transfer (PET) process. However, it gets strongly quenched in the case of Fe 2+ owing to chelation enhanced quenching (CHEQ). The probe (ChPA) causes no significant change in the fluorescence and becomes highly specific and sensitive towards Fe 3+ and Fe 2+ compared to other interfering heavy and transition metal ions (HTM). The detection limits of the sensor for the Fe 3+ and Fe 2+ are 0.124 nM and 0.138 nM, respectively. The probe is also promising as a selective sensor for the Fe 3+ and Fe 2+ in the fluorescence imaging of living cells. Thus, such a probe opens up new opportunities to improve the chitosan based fluorescent chemosensor having biocompatibility, biodegradability, sufficient thermal stability and stability in a wide pH range.