Perspectives on dual-purpose functional nanomaterials for detecting and removing fluoride ion from environmental water

Fluoride (F–) is a unique analyte because when in small quantities, it is beneficial and harmful when in larger or negligible quantities, leaving it essential for dual-purpose detection and removal from a water sample to prevent fluoride-caused health risks. F– detection and removal using organic molecules and hybrid materials are extensively reported in the literature, but very few reports discuss dual-purpose detection and removal. Functional nanomaterials (FNM) based on nanoparticles, metal-organic frameworks, and carbon dots conjugated with fluorophore moiety are largely used for these purposes. Functional groups present on nanomaterial surfaces exhibited various types of interactions such as agglomeration, electrostatic, hydrogen bonding, ion exchange, coordination and π-π stacking interactions enabling dual-purpose detection and removal of F–. These materials offer unique properties such as tunable pore structure, size, and morphology coupled with large surface area and high thermal/chemical stability. Further, this perspective review discusses prospects for sustainable technologies in addition to describing the advantages and disadvantages of using FNM based on its optical properties as well as the removal efficiency. We believe this is the first account that summarizes the single FNM that can be used for both the selective detection of F– in aqueous media as well as its efficient removal.