An imidazo[1,2-a]pyridine-functionalized xanthene fluorescent probe for naked-eye detection of Hg2+ and its application in cell imaging and test strips†

An imidazo[1,2-a]pyridine-functionalized xanthene dye (Rh-Ip) was designed and developed as a fluorescent probe (Rh-Ip-Hy) for Hg²⁺ by introducing spirolactam to the molecule. The probe Rh-Ip-Hy with a ring-closed spirolactam structure reacts with Hg²⁺ to form a fluorescent ring-opened spirolactone structure. Due to its asymmetric structure and the presence of a Lewis base site, the probe exhibits a larger Stokes shift and higher pH tolerance than the traditional xanthene dyes and probes. Furthermore, the probe is highly selective to Hg²⁺ within a wide pH range of 5.0–11.0. The probe Rh-Ip-Hy also exhibits low cytotoxicity and can be used for the detection of Hg²⁺ in living HeLa cells through fluorescence imaging. Finally, a paper-based test strip was prepared and successfully applied for the detection of Hg²⁺ in tap water and lake water samples.