A facile and green strategy for preparing newly-designed 3D graphene/gold film and its application in highly efficient electrochemical mercury assay

In this work, we report a facile and green strategy for in situ and one step preparation of a novel 3D graphene/gold (G/Au) film. Triggering with unique driving force from hydrothermal growth, a 3D interlaced graphene framework with hierarchically porous structures was directly attached on a gold substrate pretreated with a self-assembled monolayer. Simultaneously, highly dispersive Au nanoparticles with tunable morphologies were anchored on the framework utilizing generated graphene as an endogenous reductant. Newly-designed 3D G/Au film possessed excellent properties of significantly large specific area, good electrical conductivity, high structure stability and substrate binding strength, etc. As a paradigm, an electrochemical Hg²⁺ biosensor was constructed on 3D G/Au film, in which an exonuclease III-assisted target recycling was introduced. Impressively, an ultralow detection limit of 50 aM (S/N=3), a wide linear range from 0.1 fM to 0.1 μM, a high selectivity and a good reliability for Hg²⁺ assay in real water and serum samples were realized using prepared biosensor. It is highly envisioned that this work opens the door towards simply fabricating varying types of 3D graphene based hybrid films, and such G/Au film will have widespread applications in electroanalysis and electrocatalysis.