Naphthylthiourea-modified permethylcyclodextrin as a highly sensitive and selective "turn-on" fluorescent chemosensor for Hg2+ in water and living cells

A naphthylthiourea-modified cyclodextrin (1) and its urea derivative (2) were synthesized, and their fluorescence behaviors in the presence of various metal ions were investigated. Significantly, 1 showed a highly sensitive and selective fluorescence sensing ability for Hg2+ over other metal ions in both water and living cells. That is, the addition of Hg2+ to an aqueous solution of 1 gave a significantly enhanced fluorescence at similar to 380 nm. In contrast, the addition of other metal ions induced negligible fluorescence changes. The possible mechanism may be due to the transformation of thiourea to urea by Hg2+-induced desulfurization in water.