MXene quantum dots/polyethylenimine/covalent organic framework nanocomposite for selective determination of Hg²⁺ in water samples using differential pulse anodic stripping voltammetry

In this study, MXene quantum dots-functionalized polyethylenimine was composited with melamine-based covalent organic framework (MXene QDs-PEI/COF) and utilized for sensitive and selective determination of Hg²⁺ in water samples using differential pulse anodic stripping voltammetry (DPASV). The prepared pencil graphite electrode-modified MXene QDs-PEI/COF was carefully characterized with field emission scanning electron microscopy, Fourier transform infrared, X-ray diffraction, fluorescence spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry in detail. Electroactive surface area of the PGE/MXene QDs-PEI/COF was calculated to be 0.23 cm² which was remarkably improved in comparison with PGE/COF and PGE/MXene QDs-PEI with the surface areas of 0.0067 and 0.189 cm². The obtained results with DPASV technique for Hg²⁺ determination resulted a linear analytical response (R² = 0.9944) in the concentration range of 50 nM to 35 µM, with the sensitivity of 16.973 µA µM⁻¹ cm⁻² and detection limit of 16 nM (S/N = 3). The developed method was utilized carefully for mercury analysis in Caspian Seawater and tap water samples with suitable precision and accuracy.