A single fluorophore ratiometric nanosensor based on dual-emission DNA-templated silver nanoclusters for ultrasensitive and selective Pb2+ detection

Lead ion (Pb 2+ ) is known as a major non-degradable environmental pollutant and is quite harmful to human health. In our investigation, a novel ratiometric fluorescent nanosensor with DNA-AgNCs as single fluorophore has been successfully constructed for ultrasensitive and specific detection of Pb 2+ . The single-strand DNA templated silver nanoclusters present green emission, which can be converted into red emission after approaching a specific DNA segment by forming duplex with its complementary DNA strands (ds-DNA-AgNCs). The ds-DNA-AgNCs contains rA cleavage site of Pb 2+ -dependent DNAzyme configuration. In the presence of Pb 2+ , the specific DNA segment would be released from the ds-DNA-AgNCs, resulting in discoloration of DNA-AgNCs from red to green. Since Pb 2+ can successively cleave the rA site, the signal change from red to green emission is amplified. Thus, benefiting from the Pb 2+ -dependent DNAzyme and the charming properties of DNA-AgNCs, the proposed platform exhibits a good linear relationship from 0.001 nM to 10 nM with a detection limit of 1.0 pM for Pb 2+ determination, which is lower than most of the reported Pb 2+ biosensors. Moreover, this sensitive ratiometric fluorescent probe exhibits excellent selectivity toward Pb 2+ detection in real samples, such as lake water, tap water, and human serum samples, illustrating the huge potential applications for complicated samples in the future.