SERS Detection and Removal of Mercury(II)/Silver(I) using Oligonucleotide-Functionalized Core/Shell Magnetic Silica Sphere@Au Nanoparticles

Heavy metal ions, such as Hg2+ and Ag+, pose severe risks in human health and the environment. For sensitive detection and selective removal of Hg2+ and Ag+ ions, here, we demonstrate a surface-enhanced Raman scattering (SERS)-active platform by employing the oligonucleotide-functionalized magnetic silica sphere (MSS)@Au nanoparticles (NPs). This system exploits mismatched T-Hg-T and C-Ag-C bridges to capture Hg2+ and Ag+ ions, exhibiting excellent responses for Hg2+ ions in the range of 0.1-1000 nM and for Ag+ in the range of 10-1000 nM. The assay is highly selective for the target ions and does not respond to other metal ions. Additionally, the Hg2+ and Ag+ ions in this system can be effectively removed from surrounding solutions by an external magnetic field or through spontaneous precipitation. Moreover, more than 80% of the MSS@Au NPs can be easily recycled with the help of cysteine. We anticipate that the designed strategy could be extended to other analytes that can bind to DNA molecules with a high affinity, and can be used in many potential applications such as environmental renovation, toxin detection, and groundwater analysis.