A single fluorescent chemosensor for multiple targets of Cu2+, Fe2+/3+ and Al3+ in living cells and a near-perfect aqueous solution

A sulfonate-based chemosensor 1 was designed and synthesized for sensing various analytes: Cu2+, Fe2+/3+ and Al3+. Sensor 1 showed a high selectivity and sensitivity for the analytes in a near-perfect aqueous medium. Cu2+ and Fe2+/(3+) could be monitored by fluorescence quenching of 1. It had sufficiently low detection limits (1.25 mu M for Cu2+ and 3.96 mu M for Fe3+), which were below the recommended levels of the World Health Organization for Cu2+ (31.5 mu M) and the Environmental Protection Agency for Fe3+ (5.37 mu M). 1 showed the high preferential selectivity for Cu2+ and Fe3+ in the presence of competitive metal ions without any interference. Importantly, pyrophosphate could be used to distinguish Fe3+ from Cu2+. In addition, this sensor could monitor Al3+ through fluorescence emission change. Moreover, 1 was successfully applied to quantify and image Al3+ in water samples and living cells. Based on photophysical studies and theoretical calculations, the sensing mechanisms of 1 for Cu2+ and Al3+ were explained, respectively.