Dual-Emissive Carbon Dots for the Sensitive and Selective Detection of Lead Ions and Differentiation of Multiple Metal Ions

A reliable and efficient detection of metal ions such as Pb2+ is critical for pollution prevention, industrial management, and food safety. In this work, dual-emissive carbon dots (CDs) with blue and green emissions were developed as efficient sensors for the detection of lead ions. The carbon dots’ emissions could be quenched by dithizone. Upon the addition of lead ions, the fluorescence of the CDs could be recovered significantly. The limit of detection for Pb2+ could reach as low as 0.117 and 0.056 nM using the blue and green emissions, respectively. The addition of other ions under lower concentrations (10–10 to 10–6 M) did not affect the CDs’ fluorescence obviously. The changes in fluorescence could be attributed to selective binding between dithizone and lead ions. High concentrations (>10–5 M) of several metals (such as Ni2+, Zn2+, and Cu2+) resulted in noticeable fluorescence changes toward the probe, which may interfere with the detection of Pb2+. Taking advantage of principal component analysis (PCA) and a multidimensional sensing platform, differentiation of these metal ions was further achieved. The designed on–off–on strategy provides insights into the development of probes for other analytes if appropriate chelating reagents are used. The integration of the on–off–on strategy, multidimensional sensing, and chemometric analysis allows us to develop probes for the desired targets.