Dithizone-decorated reduced graphene oxide for simultaneous electroanalytical detection of lead and mercury ions in water

Reduced graphene oxide (rGO) is widely used as an electrochemical material; however, its sensing performance generally requires surface functionalization. In this study, rGO was prepared via green reduction of graphene oxide (GO) using Caesalpinia sappan extract and subsequently decorated with dithizone (Dtz) to obtain a functional electrode material for the simultaneous electrochemical detection of Pb(II) and Hg(II) ions in aqueous media. The GO, rGO, and rGO/Dtz materials were characterized by XRD, Raman and FTIR spectroscopies, SEM-EDX, and TEM. The electrochemical performance was evaluated using square wave anodic stripping voltammetry and cyclic voltammetry. The optimum sensor response was obtained at pH 5 with a deposition time of 180 s. The rGO/Dtz electrode exhibited linear responses for Pb(II) and Hg(II) in the concentration ranges of 6–16 mg/L and 8–16 mg/L, respectively, with sensitivities of 3.55 and 3.50 μA L mg −1 . The detection limits were 1.34 mg/L for Pb(II) and 1.49 mg/L for Hg(II). The sensor retained 85.4% of its initial response after 7 days of storage. In the presence of interfering ions such as Cd(II) and Cu(II), satisfactory recoveries of 96% and 103% were obtained, indicating that the proposed electrode system is suitable as a simple and green-fabricated electrochemical tool for the detection of Pb(II) and Hg(II) in moderately contaminated water samples. • rGO was prepared via green reduction using Caesalpinia sappan extract. • Dithizone was used to functionalize rGO for Pb(II) and Hg(II) detection. • The rGO/Dtz electrode showed linear responses for both metal ions. • The sensor exhibited good stability and selectivity in aqueous samples.