A carbon-dot-based dual-emission probe for ultrasensitive visual detection of copper ions

In this work, we successfully developed an ultrasensitive dual-emission fluorescent sensor (CRB) for instant visual determination of Cu2+ by modifying a Cu-sensitive rhodamine B derivative (RB) onto photostable carboxyl modified carbon dots (CDs). The RB moiety of the CRB was extremely sensitive to Cu2+ and exhibited significant orange fluorescence in 1 second, while the blue CD moiety was stable to Cu2+. As a result, significant fluorescent color transformation from blue to orange could be observed in the presence of Cu2+, which could be applied to rapid visualization of Cu2+. The CRB exhibited good selectivity and excellent sensitivity to Cu2+, and the detection limit (LOD) was estimated to be 2 ppb. Moreover, a portable test strip has been successfully developed and applied for the visual inspection of Cu2+, which provides a convenient and reliable approach to monitor Cu2+ on site without resorting to instrumental analysis.