A rhodamine based near-infrared fluorescent probe for selective detection of Cu2+ ions and its applications in bioimaging

A novel near-infrared fluorescent probe TM2 based on a rhodamine-bearing framework was disclosed with a large Stokes shift (100 nm). TM2 exhibits highly selective recognition for Cu2+ in EtOH/H2O (1 : 1, v/v) solution with a low detection limit (2.3 mu M) and a wide detection range (0-50 mu M). Detection of Cu2+ is undisturbed at physiological pH levels of 5-9. This recognition mechanism is attributed to the formation of a 1 : 1 complex between TM2 and Cu2+, validated by Job's plot, 1H NMR titration, and LC-MS experiments. Moreover, the successful fluorescence imaging of Cu2+ both in vitro and in vivo was also accomplished.