Chitosan-based fluorescein amphiphile macromolecular sensor for Hg2+ detection

Contamination of environmental water sources by heavy metals is considered a high threat to humans and plants. Detection and removal of heavy metals from wastewater are considered suitable solutions for health protection. Mercury is one of the most toxic threats among the various heavy metals in water. Herein, chitosan biopolymer was grafted by chemically modified fluorescein to obtain a fluorescent biopolymer sensor for the detection of Hg2+ metal ions in different water sources. The prepared biopolymer sensor was characterized using FTIR, 1H NMR, and XRD spectroscopy. The prepared biopolymer sensor showed high selectivity towards Hg2+ ions in the presence of several ions. The limit of detection was promising at 5.52 nM which is 5.4 times lower than the reported sensors. The recovery of Hg2+ from the medium was highly effective and followed the Freundlich adsorption isotherm according to the pseudo-second-order kinetic model. The prepared biosensor showed high efficiency and selectivity during sensing Hg2+ ions in tap water and river water. The quenching mechanism of the fluorescence process was discussed. The prepared biopolymer sensor showed negative antibacterial and antifungal efficacies, while its metal complexes by copper, cobalt, and zinc showed high efficacies with considerably low minimum inhibiting concentration. Sulfate-reducing bacteria assay of the different biopolymer sensor-metal complexes showed high efficiency towards defeating the SRB growth in an anaerobic environment.