An electrochemical aptasensor based on silver-thiolated graphene for highly sensitive detection of Pb.

The presence of lead ions (Pb) in the environment not only leads to environmental contamination but also poses a significant risk to public health through their migration into food and drinking water. Therefore, the development of rapid and effective techniques for detection of trace amounts of Pb is crucial for safeguarding both the environment and biosafety. In this study, an aptamer-based electrochemical sensor was developed for specific detection of Pb by modifying a polylysine (PLL) coated silver-thiolated graphene (Ag-SH-G) nanocomposite (PLL/Ag-SH-G) on the surface of a glassy carbon electrode, which was further modified with gold nanoparticles (AuNPs) for attachment of aptamers (Apt) that specifically recognized Pb. The Ag-SH-G particles were synthesized using a one-step method, resulting in significantly enhanced electrochemical properties upon incorporating Ag nanoparticles into the PLL/Ag-SH-G composite. Coating of the covalently or no-covalently bonded Ag-SH-G particles with PLL provides an excellent supporting matrix, facilitating the assembly of AuNPs and a thiol-modified aptamer for Pb. Under optimized conditions, Apt/AuNPs/PLL/Ag-SH-G/GCE exhibited excellent sensing performance for Pb with a wide linear response range (10-1000 nM), a low detection limit (0.047 nM) and extraordinary selectivity. The sensor was employed and satisfactory results were obtained in river water, soil and vegetable samples for the detection of Pb.