Femtomole level photoelectrochemical aptasensing for mercury ions using quercetin–copper(II) complex as the DNA intercalator

An ultrasensitive and selective photoelectrochemical (PEC) aptasensor for mercury ions was first fabricated based on perylene-3, 4, 9, 10-tetracarboxylic acid/graphene oxide (PTCA/GO) heterojunction using quercetin–copper(II) complex intercalated into the poly(dT)–poly(dA) duplexes. Both the PTCA/GO heterojunction and the quercetin–copper(II) complex are in favor of the sensitivity for the fabricated PEC aptasensor due to band alignment and strong reduction capability, respectively. And they efficiently promote the separation of photoexcited carriers and enhance the photocurrent. The formation of thymine–Hg2+–thymine coordination chemistry resulted in the dehybridization of poly(dT)–poly(dA) duplexes and then the intercalator quercetin–copper(II) complex broke away from the surface of the PEC aptasensor. As the concentration of mercury ions increased, the photocurrent gradually decreased. The electrode response for mercury ions detection was in the linear range from 0.01 pmol L−1 to 1.00 pmol L−1 with the detection limit of 3.33 fmol L−1. The label-free PEC aptasensor has excellent performances with ultrasensitivity and good selectivity besides the advantage of economic and facile fabrication. The strategy of quercetin–copper(II) complex as a novel DNA intercalator paves a new way to improve the performances for PEC sensors.