Electrochemical Aptasensor Based on Sulfur–Nitrogen Codoped Ordered Mesoporous Carbon and Thymine–Hg2+–Thymine Mismatch Structure for Hg2+ Detection

A renewable electrochemical aptasensor was proposed for super-sensitive determination of Hg2+. The novel aptasensor, based on sulfur-nitrogen codoped ordered mesoporous carbon (SN-OMC) and thymine-Hg2+-thymine (T-Hg2+-T) mismatch structure, used ferrocene as signal molecules to achieve the conversion of current signals. In the absence of Hg2+, 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 Hg2+, the hairpin structure of probe 1 was opened due to the preferential formation of the T-Hg2+-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 Hg2+ can be actualized by analyzing the relationship between the change of oxidation current caused by ferrocene signal molecules and the Hg2+ 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.