Colorimetric Detection of Lead Ion Based on Gold Nanoparticles and Lead-Stabilized G-Quartet Formation

In this report, we present a method for the detection of Pb2+ based on the different adsorption capacity on the surface of gold nanoparticles (AuNPs) between ssDNA (single-stranded DNA) and G-quartet. In the absence of Pb2+, the DNA oligonucleotides probe, which is guanine-rich ssDNA, can be adsorbed on the surface of AuNPs protecting them from aggregation. After adding Pb2+, the DNA oligonucleotides probe can specifically form compact G-quartet, which can induce the aggregation of unmodified AuNPs, especially after adding NaCl aqueous solution. Consequently, the color turns from red to blue. Pb2+ can be detected by colorimetric response of AuNPs; its detection limit can reach 5 μM only observed by naked eyes. Most metal ions have no interferences, and the interference of Cu2+ can be effectively eliminated by adding cysteine. It provides a simple and effective colorimetric sensor for on-site and real time detection of Pb2+.