β-Cyclodextrin and calix[4]arene-25,26,27,28-tetrol capped carbon dots for selective and sensitive detection of fluoride.

In this work we have designed a novel system based on carbon dots prepared from chitosan gel capped with β-cyclodextrin and calix[4]arene-25,26,27,28-tetrol for sensitive and selective detection of fluoride ions in aqueous media. Fluorescent carbon dots prepared from chitosan gel when capped with β-cyclodextrin and calix[4]arene-25,26,27,28-tetrol results in quenching of its fluorescence intensity. Introduction of F(-) ions to carbon dots capped with β-cyclodextrin and calix[4]arene-25,26,27,28-tetrol system results in enhancement and restoration of fluorescence intensity leading to detection of F(-) ion. Minimum detection limit was determined to be ∼6.6 μM. The detection is selective as with other halide ions i.e. Cl(-), Br(-) and I(-) and hydroxyl ion (OH(-)), there is observed decrease of fluorescence intensity. A possible mechanism to justify the observation is also discussed in the paper.