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 tracelevel detection and discrimination of multiple cations, viz. Al3+, Zn2+, Cd2+, and Hg2+ 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 x 10(-9) M Al3+, 1.2 x 10(-9) M Zn2+, 6.7 x 10(-9) M Cd2+, and 1.7 x 10(-10) M Hg2+, whereas the respective association constants are 1.33 x 10(5) M-1, 2.11 x 10(4) M-1, 1.35 x 10(5) M-1, and 4.09 x 10(5) M-1. The other common ions do not interfere. The probe is useful for intracellular imaging of Zn2+, Cd2+, and Hg2+ in squamous epithelial cells. RHES is useful for the determination of the ions in sea fish and real samples.