‘Turn-on’ fluorescence sensing of Al(III) ions in water using a simple N-hydroxy-4-amino-1,8-naphthalimide chemosensor

A simple fluorophore, N-hydroxy-4-amino-1,8-naphthalimide (Nap-OH), has been designed and used as a fluorescent “turn-on” chemosensor for sensing metal cations in water. Nap-OH exhibited solvent-dependent photophysics in different solvents and displayed high selectivity and reversible sensing ability for Al(III) ions with femtomolar (10−15 M) sensitivity. The initial emission intensity of Nap-OH was drastically enhanced upon the addition of Al(III) ions and the calculated Stern-Volmer binding constant (KSV) is 4.70 × 104 M−1. The selective sensing of Al(III) was also reflected by sharp visual color changes and further demonstrated the use of Nap-OH for sensing Al(III) in real-water samples.