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) (Pb2+) ions, preferably at sub-nM level due to the possible long-term accumulation of Pb2+ in the human body, which may cause serious threats to human health. However, a suitable Pb2+ sensor meeting the demands is still scanty. Herein, we develop a polyadenine-assisted, surface-enhanced Raman scattering (SERS) silicon chip (0.5 cm X 0.5 cm) composed of core (Ag)-satellite (Au) nanoparticles (Ag-Au NPs)-decorated silicon wafers (Ag-Au NPs@Si) for high-performance Pb2+ detection. Typically, strong SERS signals could be measured when DNAzyme conjugated on the SERS silicon chip is specifically activated by Pb2+, cleaving the substrate strand into two free DNA strands. A good linearity exists between the normalized Raman intensities and the logarithmic concentrations of Pb2+ ranging from 10 pM to 1 mu M with a good correlation coefficient, R-2 of 0.997. Remarkably, Pb2+ ions with a low concentration of 8.9 X 10(-12) M can be readily determined via the SERS silicon chip ascribed to its superior SERS enhancement, much lower than those (similar to nM) reported by other SERS sensors. Additionally, the developed chip features good selectivity and recyclability (e.g., similar to 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 Pb2+ ions in real systems including lake water, tap water and industrial wastewater, with the RSD value less than 12%.