A multifunctional probe for lead(II) sensing using CdSe/ZnS-luminol-conjugated Fe3O4 magnetic nanocomposites

Based on the exchange of the DNA duplex-quadruplex, a multifunctional Pb(II) ion probe was fabricated, in which Pb(II) ion-driven DNA duplexes act as a bridge to link CdSe/ZnS-luminol and Fe 3 O 4 nanoparticles . As Pb(II) ion owns a strong binding capacity for G-quadruplex (G4), it can unwind the DNA duplex and release its complementary strand. In this strategy, three detection modes, chemiluminescence (CL), fluorescence (FL) assay and colorimetric assay (CA), can be realized via DNA duplex bridged CdSe/ZnS and Fe 3 O 4 nanocomposites . Amongst, FL assay shows the best detection performance, and it exhibits a linear range of 10 nM to 10 µM, as well as the limit of detection (LOD) with 1.63 nM (n = 3, ± 3.5%). In the selective analysis, Pb(II) ion can be specifically detected in the nine different interfering metal ions . Besides, the magnetic probe requires only one “mixing and separation” operation and greatly improves the detection efficiency. The three assays can be combined as one method to achieve a simple and rapid feature. Such a three-in-one analytical platform, therefore, can serve as a powerful tool for selective, accurate and sensitive detection of Pb(II) ion.