Abstract
A rhodamine-based smart probe (RHES) has been developed for trace-level 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 × 10-9 M Al3+, 1.2 × 10-9 M Zn2+, 6.7 × 10-9 M Cd2+, and 1.7 × 10-10 M Hg2+, whereas the respective association constants are 1.33 × 105 M-1, 2.11 × 104 M-1, 1.35 × 105 M-1, and 4.09 × 105 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.