Electrochemical sensor based on Y-shaped DNA by “one-pot” method for mercury detection

A DNA electrochemical sensor based on Y-shaped DNA probes was successfully designed for Hg2+ detection. The sensor was modified with carbon self-doping graphite-like carbon nitride (C-g-C3N4) and electrodeposited gold nanoparticles (EAu) to enhance conductivity and enrich the binding sites for DNA. DNA probe (S1) binded on the modified electrode via –SH, forming a stable Y-shaped DNA double helix structure with probe S2 and probe S3 anchoring on gold nanoparticles (nanoAu) in the presence of Hg2+ solution. The Y-shaped DNA duplex, with its tight and nondeformable rigid structure, created well-defined stereoscopic reaction areas and efficiently captures Hg2+ due to its structural differences, thereby improving the signal response. Moreover, larger amounts of methylene blue (MB) could be loaded to provide adequate electrochemical response signal. The proposed sensor possessing signal amplification ability displayed a linear relationship between the square wave voltammetry (SWV) peak currents. Under the optimal conditions, Hg2+ could be detected in the range from 5000.0 to 5.0 nM with a detection limit of 8.5 pM. The sensor was also tested with tap water, river and medical wastewater samples. It showed the good recovery and accuracy and represented a promising method for Hg2+ detection.