Characterization of a Cu^2+ -selective fluorescent probe derived from rhodamine B with 1,2,4-triazole as subunit and its application in cell imaging

A rhodamine B derivative containing 1,2,4-triazole as subunit was characterized as an “off–on” type Cu^2+ - selective fluorescent probe. It exhibited high selectivity and sensitivity for Cu^2+ in ethanol–water solution (9:1, v:v, pH 7.0, 20 mM HEPES) and underwent ring opening. A prominent fluorescence enhancement at 570 nm was observed in the presence of Cu^2+ with the change in the absorption spectrum, and a 1:1 metal–ligand complex was formed. With the optimized experimental conditions, the probe exhibited a dynamic response range for Cu^2+ from 8.0 × 10 ^−7 to 7.5 × 10 ^−6 M with a detection limit of 2.3 × 10 ^−7 M in ethanol–water solution (9:1, v:v, pH 7.0, 20 mM HEPES). Its application in Cu^2+ imaging in living cells was also studied.