A rhodamine-based sensor for chromogenic detection of Cu2+ and fluorescent detection of Fe3+

Abstract

A rhodamine-benzimidazole conjugate (RB) as a probe was investigated. UV-Vis analysis showed that a strong absorption band at 552 nm was formed with the addition of Cu2+, while other transition metal ions induced a little more absorption. The absorption value of RB solution at 552 nm has a linear correlation with Cu2+ concentration between 35–70 μmol/L; the detection limit reached 6.82×10−2 μmol/L, which is lower than the settled limitation for copper in the drinking water (∼30 μmol/L) standardized by World Health Organization (WHO). Moreover, FL analysis showed that only Fe3+ could induce large fluorescence intensity enhancement at 582 nm; other common metal ions including Cu2+ cannot induce the enhancement. There was a good linear correlation between relative fluorescence intensity and Fe3+ concentration ranging from 2 μmol/L to 20 μmol/L, and the detection limit reached 1.70×10−2 μmol/L. The results showed that RB could detect Cu2+ and Fe3+ simultaneously, with the UV-Vis and fluorescence spectroscopy, respectively.