Electrochemical Aptasensor Based on Sulfur-Nitrogen Codoped Ordered Mesoporous Carbon and Thymine-Hg-Thymine Mismatch Structure for Hg Detection.

A renewable electrochemical aptasensor was proposed for super-sensitive determination of Hg. The novel aptasensor, based on sulfur-nitrogen codoped ordered mesoporous carbon (SN-OMC) and thymine-Hg-thymine (T-Hg-T) mismatch structure, used ferrocene as signal molecules to achieve the conversion of current signals. In the absence of Hg, the thiol-modified T-rich probe 1 spontaneously formed a hairpin structure by base pairing. After being hybridized with the ferrocene-labeled probe 2 in the presence of Hg, the hairpin structure of probe 1 was opened due to the preferential formation of the T-Hg-T mismatch structure, and the ferrocene signal molecules approached the modified electrode surface. SN-OMC with high specific surface area and ample active sites acted as a signal amplification element in electrochemical sensing. The sensitive determination of Hg can be actualized by analyzing the relationship between the change of oxidation current caused by ferrocene signal molecules and the Hg concentrations. The aptasensor had a fine linear correlation in the range of 0.001-1000 nM with a detection limit of 0.45 pM. The aptasensor also displayed a good response in real sample detection and provided a promising possibility for in situ detection.