A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu2 + in aqueous solution

• The rhodamine-based sensor is simple to synthesize. Its structure was confirmed by single crystal X-ray diffraction.
• This sensor can be used to determine Cu2 + ion with high selectivity and sensitivity.
• The recognition of Cu2 + gave rise to color changes from colorless to pink that was clearly visible to the naked eye.

A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu2 +. The optical feature of 1 for Cu2 + was investigated by UV–vis absorption spectroscopy. Upon the addition of Cu2 +, 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 Cu2 + 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 Cu2 + with high sensitivity.

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