Silicon nanohybrid-based SERS chips armed with an internal standard for broad-range, sensitive and reproducible simultaneous quantification of lead(ii) and mercury(ii) in real systems†
Lead ions (Pb2+) and mercury ions (Hg2+), the two commonly coexisting heavy metal ions, pose severe risks to environment and human health. To date, no surface-enhanced Raman scattering (SERS) sensor has been reported for the simultaneous quantification of Pb2+ and Hg2+ in real systems. Herein, the first demonstration of SERS chips for simultaneous quantification of Pb2+ and Hg2+ in real systems is presented based on the combination of reproducible silicon nanohybrid substrates and a corrective internal standard (IS) sensing strategy. This chip was made of a silver nanoparticle-decorated silicon wafer via modification of the IS, i.e. 4-aminothiophenol, molecules. The as-prepared chip was further functionalized with Pb2+- and Hg2+- specific DNA strands capable of simultaneously detecting Pb2+ and Hg2+. Quantitatively, upon correction by the IS Raman signals, the broad dynamic ranges from 100 pM to 10 μM for Pb2+ and from 1 nM to 10 μM for Hg2+ were achieved, with the detection limit down to 19.8 ppt for Pb2+ and 168 ppt for Hg2+. For real applications, we further demonstrated that Pb2+ and Hg2+ spiked into industrial wastewater could be readily distinguished via the presented chip, and the relative standard deviation (RSD) value was less than ∼15%. More significantly, the resulting SERS chip can be well coupled with a hand-held Raman instrument and can then be used for the qualitative analysis of both Pb2+ and Hg2+ in real systems in a portable manner. Our results suggest that this high-quality SERS chip is a powerful tool for on-site detection of various heavy metal ions in real samples in the field of food safety and environment protection.