A photo-induced electron transfer based reversible fluorescent chemosensor for specific detection of mercury (II) ions and its applications in logic gate, keypad lock and real samples

A quantitative mercuric detection is very important in the environmental and biological systems. In this paper, we report a novel bis-rhodanine derived fluorescent chemosensor for recognition of Hg²⁺ ion in DMSO-H₂O (1:1) medium. The ‘turn-on’ fluorescence response was exhibited specifically toward Hg²⁺ over other metal ions by receptor R2 at 410 nm, which could be ascribed to the restriction of photo-induced electron transfer (PET) process and chelation-enhanced fluorescence (CHEF) effect upon the complexation with mercury ions. The complexing stoichiometry of receptor R2 to Hg²⁺ was estimated to be 1:1 according to Job's plot experiments. The limit of detection was calculated to be 7.33 × 10⁻⁷ M based on the concentration dependent emission changes with good association constant of 8.97 × 10⁴ M⁻¹. As a result, we express that receptor R2 is a promising candidate for Hg²⁺ recognition without any significant interference of other co-existing cations. The receptor R2 was successfully applied to molecular logic and keypad lock applications and real water samples to determine its potential applications.