A novel rhodamine-based colorimetric and fluorescent sensor for the dual-channel detection of Cu2+ and Fe3+ in aqueous solutions

• A new rhodamine B-based dye is reported.
• The dye can be used to monitor Cu2+ and Fe3+ in aqueous solutions.
• The dye is a colorimetric and fluorescent sensor.
• The sensor has high selectivity and sensitivity.
• The sensor can be applied in a wide pH rang.

A novel xanthene dye was designed and synthesized from rhodamine B, hydrazine hydrate and 4-chloro-7-nitro-2,1,3-benzoxadiazole. The sensing activity of the new rhodamine dye toward metal ions was carefully investigated. In H2O/CH3CN (1/1, v/v), the dye showed high selectivity and sensitivity to Cu2+ by remarkable absorption and fluorescence enhancement, while in H2O/CH3CN (99/1, v/v), the dye behaved as a high selective and sensitive turn-on fluorescent sensor for Fe3+. The detection was essentially insensitive to H+ concentration between pH 2.6 and 10.9. The sensing mechanism was explored by IR and LC–mass spectroscopic techniques and the LC–mass analysis results indicated that a 1:1 complex was formed between Cu2+ (or Fe3+) and the sensor.