Dielectric-metal hybrid structured LSPR sensor based on graphene oxide amplification for lead ion detection

The detection of lead ions (Pb²⁺) is crucial due to its harmful effects on health and the environment. In this article, what we believe to be a novel dielectric-metal hybrid structure localized surface plasmon resonance (LSPR) sensor for ultra-trace detection of Pb²⁺ is proposed, featuring a zinc sulfide layer, silver nanodisks (Ag-disks), and graphene oxide (GO) covering the Ag-disks. The sensor works by detecting the variation of gold nanoparticles (AuNPs) on its surface when Pb²⁺ cleaves a substrate strand linked to a DNAzyme, causing the AuNPs modified on the substrate strand to disperse. The LSPR sensor boasts superior performance with a bulk refractive index sensitivity of 714.34 nm/RIU. It also exhibits a log-linear response to Pb²⁺ concentrations ranging from 10 pM to 100 nM, with a sensitivity of 3.93 nm/log(µM) and a detection limit of 10 pM. This represents a 1.25-fold increase in sensitivity and an order of magnitude lower detection limit compared to the GO-uncoated sensor. The improved performance is due to the abundant reactive groups and expansive surface area of graphene oxide, which facilitate the absorption of biochemical molecules. In addition, the sensor has good specificity and stability, holding significant potential for a variety of practical applications, and paving the way for LSPR sensors in detecting trace heavy metal ions.