Development of an origami paper-based electrochemical sensor using N-doped graphene for simultaneous detection of Cd(II), Pb(II), and Hg(II) in water

Abstract

Heavy metals expose great hazards to the ecological environment and public health due to their high toxicity and non-biodegradability. In this work, a low-cost, portable origami electrochemical microfluidic paper-based analytical device (EµPAD) was developed using nitrogen-doped graphene (NG) for simultaneous detection of Cd(II), Pb(II), and Hg(II) in water. The origami structure functions as a valve between sample introduction and detection, reducing sample volume and enhancing operation convenience. Electrochemical linear scanning voltammetry was employed for the first time in the in-situ synthesis of NG on paper-based electrode for sensing heavy metal ions. With its large specific surface area and numerous active sites, NG-modified electrodes exhibited excellent analytical performance for simultaneous determination of Cd(II), Pb(II), and Hg(II). The EµPAD sensor exhibited a wide linear response ranging from 5 to 100 µg/L, and low detection limits (Cd(II): 0.5698 µg/L, Pb(II): 0.4024 µg/L, Hg(II): 0.2565 µg/L,), which were well below the drinking water standards. Additionally, the EµPAD has been successfully applied to real water samples, achieving recoveries of 96.4 % ∼106.2 % with RSDs below 7 %.