Rapid and sensitive detection of Hg²⁺ with a SERS-enhanced lateral flow strip

Mercury ions are some of the most toxic heavy metal ions widely distributed in the environment. Hg²⁺ cannot be degraded by microorganisms and can accumulate in the body through the food chain, posing a great threat to human health. Herein, a method combining surface-enhanced Raman scattering (SERS) with a lateral flow strip (LFS) (SERS-LFS) was developed for the rapid and quantitative analysis of Hg²⁺. The recognition of Hg²⁺ by the LFS depends on a specific T-Hg-T strategy. Rhodamine 6G (R6G), as a SERS reporter, was assembled on the surface of Au@Ag core-shell nanoparticles, which served as an effective SERS substrate on both the T and C lines of the LFS. Using this SERS-LFS, the presence of target Hg²⁺ could be measured through the appearance of an orange color on the T line of the LFS. Furthermore, with the direct measurement of SERS on the T lines of the LFS, the SERS signal could be collected even at a low concentration of Hg²⁺, at which point the signal on the T lines could not be observed. Based on the intensities of the characteristic peak at 1513 cm^-1 of R6G collected on the T lines of the LFS, a linear relationship was obtained in the range of 0.01 nM to 1 nM, and the detection limit of the LFS was greatly improved by at least 20 times over the colorimetric results of the traditional LFS based on naked-eye observation. More importantly, this SERS-LFS did not affect the intrinsic simplicity of the LFS. This developed SERS-LFS holds great potential in practical routine screening in food safety and environmental monitoring.