Ultra-sensitive electrochemical aptasensor based on zeolitic imidazolate framework-8 derived Ag/Au core-shell nanoparticles for mercury detection in water samples

Mercury(II) is one of the most toxic heavy metals ion that is widely distributed in environment. Therefore, mercury(II) detection in environments is critical. In this study, an electrochemical aptasensor based on Au electrode (AE) was developed for mercury detection using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). To improve the performance of the aptasensor, Zeolitic Imidazolate Framework-8 (ZIF-8)-derived Ag@Au core-shell nanoparticles (Ag@Au/ZIF-8), as an aptasensor modifier, was synthesized and characterized by various techniques. It was shown that Ag@Au core-shell nanoparticles could support the covalent attachment of the aptamers on the electrode surface, and ZIF-8 as a substrate can provide a large surface area to uniform and non-agglomerated distribution of Ag@Au core-shell nanoparticles. By drawing the calibration curve for different concentrations of Hg- (2+) under optimal experimental conditions, wide linear ranges of 1.0 x 10(-16) - 1.0 x 10(-12) M and 5.0 x 10(-16)-1.0 x 10(-17) M were obtained when using DPV and EIS, respectively. Also, the developed electrochemical aptasensor exhibited a superior ultra-low detection limit of 1.8)+/- 0.04(x 10(-17) M Hg2+ with DPV method and 1.3(+/- 0.01) x10(-16) Hg(2)(+ )when using EIS, with a promising application in water samples. The relative standard deviations (RSD) were lower than 2.6 % (n = 3, using certified validation at the confidence level of 95.0 %), and with recoveries ranging from 96.0 % to 102.0 %. The repeatability of the proposed aptasensor to determine 5.0 fM Hg(2+ )was calculated as 3.9 %. (n = 5).

Automated summary

An electrochemical aptasensor based on Ag@Au/ZIF-8 modifier was developed successfully for mercury(II) detection, showing low detection limits and excellent repeatability.