Preparation of fluorescein-based chemosensors and their sensing behaviors toward silver ions

Abstract

Two fluorescein-based fluorescent chemosensors L1 and L2 have been synthesized successfully by simultaneously introducing two functional groups as metal ion bonding sites on the 4,5-positions of fluorescein via a one-pot Mannich-type reaction. The chemosensors exhibit high selectivity and sensitivity for Ag⁺ ions due to the high thiophility and selenophility of silver ions. The detection mechanism is based on the Ag⁺-induced ring opening process of the spironolactone of the fluorescein fluorophore. The stoichiometry of the complex between the sensor and Ag⁺ is indicative of a 1 : 2 ratio which was determined by a Job's plot yielded from fluorescence titrations.