A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu(2+) in aqueous solution.

A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu(2+). The optical feature of 1 for Cu(2+) was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu(2+), the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu(2+) complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 µM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu(2+) with high sensitivity.