Non-covalently functionalised rGO–fluorescein unit for selective detection of fluoride ions

Abstract

The combination of reduced Graphene oxide and Fluorescein dye serves as a highly selective optical switch for sensing fluoride ion via colorimetric and fluorimetric modes. A turn off stage viz., quenching of optical signal of fluorescein was observed by the formation of a supramolecular assembly between reduced graphene oxide (host matrix) and the dye (indicator). This OFF stage was turned ON instantly with the advent of fluoride ion (guest), with high selectivity. The limit of detection values obtained are 4.2 ppm and 1.7 ppb respectively, via colourimetric and fluorimetric strategy. Solid state test strips of the sensor unit could detect fluoride in aqueous media at concentration down to 3 ppm with the help of UV source.