Ultrasensitive, Specific, Recyclable, and Reproducible Detection of Lead Ions in Real Systems through a Polyadenine-Assisted, Surface-Enhanced Raman Scattering Silicon Chip.

It is of great significance to accurately and reliably detect trace lead(II) (Pb(2+)) ions, preferably at sub-nM level due to the possible long-term accumulation of Pb(2+) in the human body, which may cause serious threats to human health. However, a suitable Pb(2+) sensor meeting the demands is still scanty. Herein, we develop a polyadenine-assisted, surface-enhanced Raman scattering (SERS) silicon chip (0.5 cm × 0.5 cm) composed of core (Ag)-satellite (Au) nanoparticles (Ag-Au NPs)-decorated silicon wafers (Ag-Au NPs@Si) for high-performance Pb(2+) detection. Typically, strong SERS signals could be measured when DNAzyme conjugated on the SERS silicon chip is specifically activated by Pb(2+), cleaving the substrate strand into two free DNA strands. A good linearity exists between the normalized Raman intensities and the logarithmic concentrations of Pb(2+) ranging from 10 pM to 1 μM with a good correlation coefficient, R(2) of 0.997. Remarkably, Pb(2+) ions with a low concentration of 8.9 × 10(-12) M can be readily determined via the SERS silicon chip ascribed to its superior SERS enhancement, much lower than those (∼nM) reported by other SERS sensors. Additionally, the developed chip features good selectivity and recyclability (e.g., ∼11.1% loss of Raman intensity after three cycles). More importantly, the as-prepared chip can be used for accurate and reliable determination of unknown Pb(2+) ions in real systems including lake water, tap water and industrial wastewater, with the RSD value less than 12%.