Impedimetric Hg~(2+) Detection on Multilayered Reduced Graphene Oxide-Modified Electrode

摘要

Recent efforts toward the development of electrochemical biosensors have emphasized the incorporation of nano-materials, such as carbon nanotubes, metal nanoparticles, and graphene into the electrode. This incorporation, particularly of graphene, significantly improves the sensor sensitivity and selectivity. Graphene, a single-atom-thick two-dimensional sp~2 carbon network material, serves as a good support for biomolecules due to its flat surface, large surface area, and rich π-conjugation structure. The combination of graphene and DNA has attracted much interest in the biosensor field. Recently, the interaction between hairpin DNA (hp-DNA) and graphene surface have been used to detect single nucleotide polymorphisms (SNP). Hp-DNA is a secondary DNA structure in which two regions of the same DNA strand form base-pairs in a double helix capped by an unpaired loop. The presence of the unpaired loop permits hp-DNA to readily adsorb onto graphene surfaces. The development of efficient methods for detection of trace Hg~(2+) is of significant importance for human health and the environment because Hg~(2+) is an extremely toxic heavy metal ion. Numerous strategies including optical and electrochemical methods for the detection of Hg~(2+) have been developed. Among them, electrochemical impedance spectroscopy (EIS) as a label-free method, is highly attractive for biosensing assay due to its high sensitivity and simplicity.