A dual functional probe for “turn-on” fluorescence response of Pb2+ and colorimetric detection of Cu2+ based on a rhodamine derivative in aqueous media

A dual functional probe L based on rhodamine was devised and synthesized. Probe L can sense Pb2+ and Cu2+ in aqueous solution through two approaches: a significant fluorescence enhancement caused by Pb2+ and a visible color change from colorless to orchid induced by Cu2+. Competitive experiments showed that probe L had high fluorescence sensitivity for Pb2+ and excellent colorimetric selectivity for Cu2+ over many environmentally relevant ions. The mechanisms of L for sensing Pb2+ and Cu2+ have been well demonstrated by ESI-MS, H-1 NMR titration, IR, the crystal structure of L-Pb2+ and density functional theory calculation of L-Cu2+. In addition, fluorescence image detection of Pb2+ in living cells displayed an enhanced fluorescence effect.