Single cytosine-based electrochemical biosensor for low-cost detection of silver ions

Three-electrode system was microfabricated on a glass wafer. SC was immobilized on the working electrode surface, and then this electrode was exposed to a solution with Ag ions and other SC for mismatching cytosine-Ag+-cytosine. Before detecting Ag ion, cyclic voltammetry and energy-dispersive X-ray spectroscopy were used for the identification of stable immobilization of SC on the surface of the functionalized Au electrode. The electrochemical analysis for increasing Ag ion concentration and the Ag+ selectivity of the SC probe were performed by square wave voltammetry. The resulted current increase is linear with the logarithmic concentration of Ag ion from 0.5 nM to 1 mM with ∼20 pM of detection limit. The slope of in a target concentration range mentioned above are 9.14 × 10−2 per concentration decade with R2 value of 0.9814. The reason why our system has a lower detection limit than the previous studies is because the bound each single Ag ion performs a path role for electron transfer. Moreover, the proposed electrochemical assay has good selectivity to other environmentally relevant metal ions.