Disposable Faraday cage-type aptasensor for ultrasensitive determination of sub-picomolar Hg(II) via fast scan voltammetry

•Fast scan voltammetry was used to improve the detection sensitivity of aptasensors first time.•Faraday cage-type aptasensor for the detection of metal ions was built first time.•Hg(II) could be detected ultrasensitively with a LOD of 0.03 pmol/L. A disposable Faraday cage-type aptasensor for ultrasensitive determination of sub-picomolar Hg(II) was developed based on fast scan voltammetry (FSV). Signal unit rGO-AFc@AuNPs-DNA was designed, in which aminoferrocene (AFc) is the signal label, gold nanoparticles (AuNPs) improve the conductivity of rGO and combine DNA through Au-S bond, DNA could selectively capture Hg(II) with DNA3 through the formation of thymine-Hg(II)-thymine (T-Hg(II)-T) complex, and rGO provides the basis for loading above functional components. In presence of Hg(II), the signal unit could be immobilized on the disposable electrode through T-Hg(II)-T mismatch to build a Faraday cage-type aptasensor, and the scan rate of 400 V/s was used by FSV, resulting in ultrasensitive determination of Hg(II) in concentration range from 0.1 μmol/L to 0.1 pmol/L with a limit of detection (LOD) 0.03 pmol/L. The sensitivity is greatly improved due to the following points: a large number of signal labels AFc are immobilized, conductive rGO allows all AFc immobilized to participate in the electrode reaction, and a high scan rate is used. Satisfied stability, selectivity and accuracy were obtained. Thus, this proposed disposable Faraday cage-type aptasensor provides a new path to ultrasensitive on-site rapid determination of Hg(II) or analog heavy metal ions.