A fluorescent chemosensor for Hg2+ based on naphthalimide derivative by fluorescence enhancement in aqueous solution

Naphthalimide derivative (compound 1) containing hydrophilic hexanoic acid group was synthesized and used to recognize Hg(2+) in aqueous solution. The fluorescence enhancement of 1 is attributed to the formation of a complex between 1 and Hg(2+) by 1:1 complex ratio (K=2.08×10(5)), which has been utilized as the basis of fabrication of the Hg(2+)-sensitive fluorescent chemosensor. The comparison of this method with some other fluorescence methods for the determination of Hg(2+) indicated that the method can be applied in aqueous solution rather than organic solution. The analytical performance characteristics of the proposed Hg(2+)-sensitive chemosensor were investigated. The chemosensor can be applied to the quantification of Hg(2+) with a linear range covering from 2.57×10(-7) to 9.27×10(-5) M and a detection limit of 4.93×10(-8) M. The experiment results show that the response behavior of 1 toward Hg(2+) is pH independent in medium condition (pH 4.0-8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Hg(2+) in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward Hg(2+) is fast (response time less than 1 min). In addition, the chemosensor has been used for determination of Hg(2+) in hair samples with satisfactory results, which further demonstrates its value of practical applications.