Highly Sensitive Detection and Removal of Lead Ions in Water Using Cysteine-Functionalized Graphene Oxide/Polypyrrole Nanocomposite Film Electrode

Abstract

We synthesized cysteine-functionalized graphene oxide (sGO) using carbonyldiimidazole as a cross-linker via amide and carbamate linkages. The sGO/polypyrrole (PPy) nanocomposite film was grown on the working electrode surface of a screen-printed electrode (SPE) via controlled one-step electrochemical deposition. The sGO/PPy-SPE was used to detect lead ions (Pb²⁺) in water by first depositing Pb²⁺ on the working electrode surface for 10 min at −1.2 V, and then anodic stripping by differential pulse voltammetry (DPV). The DPV signals were linear in the ranges of 1.4–28 ppb (<i>R</i>² = 0.994), 28–280 ppb (<i>R</i>² = 0.997), and 280–14 000 ppb (<i>R</i>² = 0.990) Pb²⁺. The measurable detection limit of the sensor is 0.07 ppb (<i>S</i>/<i>N</i> = 3), which is more than 2 orders of magnitude below the 10 ppb threshold for drinking water set by the World Health Organization. The average removal efficiency of Pb²⁺ deposited on the electrode was 99.2% (<i>S</i>/<i>N</i> = 3), with relative standard deviation (RSD) of 3.8%. Our results indicate good affinity of sGO/PPy nanocomposite to Pb²⁺, which can be used to effectively adsorb and remove Pb²⁺ in water samples. Therefore, sGO/PPy nanocomposite we synthesized is useful for highly sensitive on-site and real-time monitoring of heavy metal ions and water treatment