Hg2+-induced hydrolysis of fluorescein hydrazone: A new fluorescence probe for selective recognition Hg2+ in an aqueous solution

Abstract

In this study, we report the synthesis of a new fluorescent probe, developed for the sensitive detection of Hg²⁺ in aqueous environments. The probe molecule was thoroughly characterized by several spectral methods. The probe derived from fluorescein hydrazide and 2,4-dimethoxybenzaldehyde demonstrate a significant increase in fluorescence emission and absorbance upon interaction with Hg²⁺ions. This response is attributed to converting the closed spirolactam form to the open form of the fluorescein ring. The sensing mechanism was elucidated through ¹H NMR and MALDI-TOF MS analyses revealing Hg²⁺-promoted hydrolysis of the fluorescein hydrazone. The conformational diversity of the probe, which affects its spectral properties, was analyzed using quantum chemical methods. Notably, the probe displayed excellent selectivity towards Hg²⁺, a low detection limit of 0.16 µM, and a rapid response time. Furthermore, it was successfully employed to monitor variations in Hg²⁺ concentrations in river water samples, highlighting its potential application in environmental monitoring and safety assessments.