α-Ni(OH)2/PEI nanocomposite for heavy metal ion sensing

Abstract

Most of the heavy metals are highly toxic and detrimental to human health due to their non-biodegradable nature, even at very low concentrations. Heavy metal contamination as a consequence of industrialization and urbanization is one of the most serious environmental problems which leads to harmful effects on the entire ecosystem. Therefore, it is extremely important and necessary to design new materials, which exhibit ultrasensitivity in the detection of heavy metal ions. In this work, three-dimensional (3D) hierarchical flower-like Į-Ni(OH)2 nanocrystals have been successfully synthesized by intercalating anionic surfactants between the layers using a simple hydrothermal method. Į-Ni(OH)2/PEI nanohybrid was further prepared by the functionalization of polyethyleneimine (PEI) on the surface of 2D Į-Ni(OH)2 nanosheets through exfoliation-reassembling synthetic strategy. The as-prepared Į-Ni(OH)2 and Į-Ni(OH)2/PEI nanomaterials were characterized by powder XRD, FT-IR spectroscopy, and fieldemission scanning electron microscopy. Multiple physical characterizations have confirmed that the PEI molecules are successfully immobilized on the surface of exfoliated nanosheets due to strong electrostatic interactions between the nitrogen atom and nickel nanosheets. The resulting nanocomposite has been explored for the selective and sensitive detection of heavy metal ions, as it exhibits superior electrochemical properties due to its large specific surface area, effective charge transfer efficiency, the high adsorption capacity of hierarchical Į-Ni(OH)2, and excellent affinity of heavy metals ions on PEI. The electrochemical performance and stripping response for Pb(II) detection were studied using square wave anodic stripping voltammetry (SWASV). Operational parameters, including the pH value of supporting electrolyte, deposition time, and deposition potential, were also ii optimized. The Į-Ni(OH)2/PEI modified electrode exhibits a low detection limit of 0.072 µM and high repeatability with 0.916% of relative standard deviation, which is well below the standard permissible values. The result shows that hybrid materials modified electrode possesses high sensitivity, good selectivity, stability, and low limit of detection. Therefore, the proposed hybrid electrode can be a promising material for the ultrasensitive detection of heavy metals.