An electrochemiluminescence biosensor for sensitive and selective detection of Hg²⁺ based on π-π interaction between...

A solid-state electrochemiluminescence (ECL) biosensor based on a DNA-modified electrode platform that depends on the variation of π-π interaction before and after the binding of target analytes is put forward. The single-stranded DNA (ssDNA) probe was successfully assembled on the surface of a glassy carbon electrode (GCE), which was pre-modified with Ru(bpy)₃ ²⁺ complex and gold nanoparticles (GNPs). The ssDNA probe could strongly adsorb graphene due to the strong π-π interaction between nucleotides and graphene (GN), while in the presence of Hg²⁺, the conformational transformation of DNA from a single-stranded to a double-stranded structure resulted in inhibited adsorption of GN. With thymine (T)-rich ssDNA as a Hg²⁺ probe, we prepared the ECL biosensor by using ferrocene-graphene (Fc-GN) as a quenching unit to quench the ECL emission of Ru(bpy)₃ ²⁺, and the Hg²⁺ can be detected by quenching efficiency transformation when the Fc-GN gets away from Ru(bpy)₃ ²⁺. The biosensor exhibited a sensitive response to various ranges of concentration of Hg²⁺ with a detection limit of 18 pM. The ECL biosensor held great promise in the highly sensitive and selective detection of Hg²⁺ in natural water.