Exploring the Scope of Photo-Induced Electron Transfer–Chelation-Enhanced Fluorescence–Fluorescence Resonance Energy Transfer Processes for Recognition and Discrimination of Zn2+, Cd2+, Hg2+, and Al3+in a Ratiometric Manner: Application to Sea Fish Analysis

A rhodamine-based smart probe ( RHES ) has been developed for trace-level detection and discrimination of multiple cations, viz. Al 3+ , Zn 2+ , Cd 2+ , and Hg 2+ in a ratiometric manner involving photo-induced electron transfer-chelation-enhanced fluorescence-fluorescence resonance energy transfer processes. The method being very fast and highly selective allows their bare eye visualization at a physiological pH. The optimized geometry and spectral properties of RHES and its cation adducts have been analyzed by time-dependent density functional theory calculations. RHES detects as low as 1.5 × 10 -9 M Al 3+ , 1.2 × 10 -9 M Zn 2+ , 6.7 × 10 -9 M Cd 2+ , and 1.7 × 10 -10 M Hg 2+ , whereas the respective association constants are 1.33 × 10 5 M -1 , 2.11 × 10 4 M -1 , 1.35 × 10 5 M -1 , and 4.09 × 10 5 M -1 . The other common ions do not interfere. The probe is useful for intracellular imaging of Zn 2+ , Cd 2+ , and Hg 2+ in squamous epithelial cells. RHES is useful for the determination of the ions in sea fish and real samples.