A fully integrated fast scan cyclic voltammetry electrochemical method: Improvements in reaction kinetics and signal stability for specific Ag(I) and Hg(II) analysis

•A fully integrated FSCV electrochemical method is developed.•This proposed method is to improve reaction kinetics and signal stability.•TdT-yielded DNAs can be used to construct electrode substrate favorably.•The platform is suited for Ag(I) and Hg(II) analysis well.•The method is conducive to the development of the real-time detection device. Inspired by the urgent need to detect trace heavy metal ions in various real samples, we construct a unique electrochemical biosensing method for heavy metal ions Ag(I) and Hg(II) analysis in this work. The biosensor is constructed by using terminal deoxynucleotidyl transferase (TdT) to catalyze the addition of dCTP and dTTP in 3′-OH end of original DNAs, thus producing enough long DNAs. This unique DNAs have a strong affinity to Ag(I) and Hg(II), and C-Ag(I)-C and T-Hg(II)-T structures occurs at the electrode surface. Meanwhile, the introduction of fast-scanning cyclic voltammetry (FSCV) can achieve the stable signal output all the while, where the reaction kinetics are superior to the diffusion kinetics, resulting in a significant improvement on reaction kinetics and signal stability. Based on it, simple detection of Ag(I) or Hg(II) is demonstrated powerfully with good detection limit (3 × 10−14 M or 3 × 10−15 M, S/N = 3); additionally, simultaneous detection of Ag(I) and Hg(II) is achieved with negligible interference. Furthermore, the proposed method has been also applied for some DNA electronic computing logic gates by designing simple or multiple inputs and output favorably. Based on these, the FSCV method has potential applications for the monitoring of heavy metal ions in real sample analysis.