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

Abstract 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.